Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s00248-023-02261-3

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s00374-023-01743-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s00374-023-01733-5

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.crope.2022.09.002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

An in situ model paddy field experiment was conducted using non-contaminated soil to identify factors that locally increase the radiocesium activity concentrations in rice near the water inlet of paddy fields. The results demonstrated that irrigation water intake reduced exchangeable potassium concentration and increased radiocesium activity concentration in the soil near the water inlet; thus, the radiocesium activity concentration in rice was negatively correlated with the former and positively with the latter. Exchangeable potassium flushing and deposition of suspended solids in the soil owing to irrigation water intake facilitated the transfer of radiocesium to rice plants near the water inlet.

DOI： 10.1007/s10967-022-08448-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Countermeasures to reduce radiocesium uptake by crops have been implemented in farmlands affected by the accident at Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Plant in 2011. A widely practiced countermeasure is the application of K. Long-term maintenance of soil K is crucial due to the long physical half-life of Cs-137 (30 years). Plant-available K budgets can be used as an indication of sustainable maintenance. Our previous study found that large water outflow, especially percolation, associated with excessive irrigation caused major K outflow and a negative K budget in a paddy field in Fukushima in 2018. The present study evaluated whether decreasing the water outflow by reducing the irrigation volume from 6300 to 1900 mm reduced K outflow and improved the K budget in the field during the cropping period in 2019. K concentrations in soil solution were comparable in both years, and the percolation water volume decreased to 37% that of 2018, resulting in a 53% reduction in the K output from 392 to 184 kg ha(-1). The input via irrigation also decreased (-35 kg ha(-1)), but the output via surface runoff showed a greater reduction (-58 kg ha(-1)) owing to a 70% decrease in the water volume compared with 2018. Consequently, the K budget was substantially improved (from -289 to -57 kg ha(-1)), highlighting the importance of controlling water outflow, particularly percolation, for soil K maintenance in paddy fields with high permeability.

DOI： 10.1080/00380768.2022.2108685

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DOI： 10.1007/s10967-022-08350-w

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Environmental pollution by microplastics (MPs) has become a global problem, but little is known about MPs in soils. This is because MP extraction methods from soils have not yet been standardized. In this study, we tried to establish a simple and economical method to extract soil MPs using the buoyancy of canola oil and the density separation process using sodium chloride (NaCl). In addition, the incineration method was adapted to evaluate the effectiveness of extraction methods precisely. First, the ability and suitability of seven different oils to extract MP from soil were investigated and canola oil was selected. Then, the spiking and recovery test was performed with canola oil and NaCl solution for low-density polyethylene (LDPE), polypropylene (PP), and polyvinylchloride (PVC) as follows: (1) soil and MP mixtures were prepared, (2) 5 g L−1 NaCl and canola oil were added and shaken thoroughly, (3) the oil phase containing MPs were separated after sedimentation, (4) the extracted MPs were rinsed with 99.5% ethanol, and (5) the organic adherents to the extracted MPs were digested with hydrogen peroxide. After drying and incineration, the substantial recovery rates were calculated. In the spiking and recovery test for MP particles (<1 mm) from five typical Japanese agricultural soils, the recoveries of LDPE, PP, and PVC were 95.2–98.3%, 95.2–98.7%, and 76.0–80.5%, respectively, higher than those obtained by the density separation using saturated NaCl solution. In conclusion, the method is effective for extracting MPs, especially LDPE and PP, from soils and is less sensitive to soil type, texture, and physicochemical properties.

DOI： 10.3390/soilsystems6020054

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s00374-022-01619-y

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.scitotenv.2021.150246

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s00374-021-01611-y

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.soilbio.2021.108397

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.rhisph.2021.100357

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.soilbio.2021.108186

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s00374-020-01523-3

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s00374-020-01525-1

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Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s00374-020-01502-8

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

To identify the cause of the phenomenon that rice plants close to the water inlet contain relatively higher radiocesium within a paddy field plot, we conducted a field experiment by establishing experimental channel using polypropylene corrugated sheets, and sampling surface water, paddy soil and rice plants according to the distance from the water inlet in 2014 and 2015. It was found that the 137Cs activity concentrations in both dissolved and particulate forms in paddy surface water presented a declining trend from the water inlet towards the outlet. The 137Cs activity concentration in paddy soil in the harvesting season and those of brown rice and rice straws were highest at 1-2 m from the water inlet. Balance calculation suggests that destination of the lost 137Cs from the surface water was likely to be adsorption of the dissolved form and sedimentation of particulate form onto the soil. The concentration of exchangeable potassium ion in paddy soil was below the recommended standard of 250 mg kg-1 (as K2O in dry soil) near the water inlet at the harvesting period both years．These findings suggested that the possible crucial factors to induce rice plant uptake of radiocesium near the water inlet were either (1) direct absorption of dissolved 137Cs in surface water by rice plants, (2) absorption of 137Cs, which was originally retained in particulate matter and released by ion exchange and/or by organic matter decomposition in combination with (3) loss of soil exchangeable potassium caused due partly to transportation of soil particles with exchangeable potassium by the rapid water flow near the water inlet and/or leaching by ion exchange onto the soil of other cations such as calcium ion flowing into the paddy field. These findings will contribute to providing possible measures for producing safe rice in highly contaminated areas in which agricultural production will resume in the near future. We propose providing a non-planting zone for the area closer than about 5 m from the water intake to avoid the occurrence of high 137Cs concentrations in rice crops.

DOI： 10.1016/j.jenvrad.2020.106441

PubMed

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.apsoil.2020.103599

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s42161-020-00503-8

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：一般社団法人 日本土壌肥料学会  

DOI： 10.20710/dohikouen.65.0_135_2

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Language：English   Publishing type：Research paper (scientific journal)  

Salinity critically limits rice metabolism, growth, and productivity worldwide. Improvement of the salt resistance of locally grown high-yielding cultivars is a slow process. The objective of this study was to develop a new salt-tolerant rice germplasm using speed-breeding. Here, we precisely introgressed the hst1 gene, transferring salinity tolerance from "Kaijin" into high-yielding "Yukinko-mai" (WT) rice through single nucleotide polymorphism (SNP) marker-assisted selection. Using a biotron speed-breeding technique, we developed a BC3F3 population, named "YNU31-2-4", in six generations and 17 months. High-resolution genotyping by whole-genome sequencing revealed that the BC3F2 genome had 93.5% similarity to the WT and fixed only 2.7% of donor parent alleles. Functional annotation of BC3F2 variants along with field assessment data indicated that "YNU31-2-4" plants carrying the hst1 gene had similar agronomic traits to the WT under normal growth condition. "YNU31-2-4" seedlings subjected to salt stress (125 mM NaCl) had a significantly higher survival rate and increased shoot and root biomasses than the WT. At the tissue level, quantitative and electron probe microanalyzer studies indicated that "YNU31-2-4" seedlings avoided Na+ accumulation in shoots under salt stress. The "YNU31-2-4" plants showed an improved phenotype with significantly higher net CO2 assimilation and lower yield decline than WT under salt stress at the reproductive stage. "YNU31-2-4" is a potential candidate for a new rice cultivar that is highly tolerant to salt stress at the seedling and reproductive stages, and which might maintain yields under a changing global climate.

DOI： 10.3390/ijms20102585

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Soil bacterial community compositions and temporal changes in organic paddy fields were elucidated using a 16S rRNA gene amplicon sequencing analysis with a high-throughput next generation sequencer. At transplanting, bacterial community compositions in organic and conventional paddy fields were mostly similar despite differences in field management. The bacterial community composition in organic fields differed from that under conventional management during the rice growth period, possibly as a result of the decomposition process of organic fertilizers. However, differences in the frequency of tillage and photosynthetic bacterial inoculations in the organic plots had less of an impact on bacterial communities.

DOI： 10.1264/jsme2.ME18101

PubMed

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Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor and Francis Ltd.  

This study evaluated three Trichoderma strains (T. harzianum TR05, T. virens TR06 and T. asperellum TR08) originating from Bangladesh as potential biological control agents against collar rot of tomato under greenhouse conditions. After seed treatment with TR05, a disease incidence of collar rot (5.36%) was lower than for TR06 (34.2%) and TR08 (20.8%). Germination percentage of tomato was highest for TR05 (90.3%). In soil treatment, inoculation with TR08 resulted in the lowest disease incidence (9.78%), and the disease incidence was statistically no different from that for TR05 (16.4%). Thus, TR05 and TR08 have potential as biological control agents of collar rot in tomato.

DOI： 10.1080/03235408.2016.1265243

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

In this research, we evaluated the range of Cs-137 discharge rates from paddy fields during land preparation and mid-summer drainage. First, we investigated Cs-137 discharge loads during land preparation and mid-summer drainage and their ratio to the Cs-137 inventory of paddy field soil. We found that total discharge rates were 0.003-0.028% during land preparation and 0.001-0.011% during mid-summer drainage. Next, we validated the range of obtained total discharge of Cs-137 from the paddy fields using a simplified equation and literature review. As a result, we conclude that the range of total outflow loads of suspended solids for the investigated paddy field was generally representative of paddy fields in Japan. Moreover, the Cs-137 discharge ratio had a wide range, but was extremely small relative to Cs-137 present in paddy field soil before irrigation. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jenvrad.2016.01.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Mediterranean Turkey has long been at the forefront of Turkish agriculture and the use of organochlorinated pesticides (OCPs) in this area rose considerably between the 1940s and 1980s. This study aimed to determine OCP residue levels in agricultural soils collected from the Mersin and Adana Districts, Cukurova Basin in Mediterranean Turkey. Most soil samples were contaminated with one, or both, of two OCP metabolites; 4,4'-dichlorodiphenyldichloroethylene (4,4'-DDE) and endosulfan sulfate. 4,4'-DDE occurred in 27 of the 29 samples and ranged from 6 to 1090 A mu g kg(-1)-dry soil (ds)(-1), while six samples contained endosulfan sulfate ranging between 82 and 1226 A mu g kg(-1)-ds(-1). Generally, horticultural and corn-planted soils contained only 4,4'-DDE, whereas greenhouse cultivation appeared to accumulate both residues. This study indicated that 4,4'-DDE occurred above acceptable levels of risk in agricultural soils of Mersin District and further studies on the qualitative and quantitative assessment of OCPs in other agricultural regions with intensive pesticide use are necessary to fully understand the impact of OCPs on agricultural soil in Turkey.

DOI： 10.1007/s00128-015-1714-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor and Francis Ltd.  

Nineteen Trichoderma isolates, collected from different locations in Bangladesh, were characterised through phenotypic, biochemical and molecular means. Besides, they were assessed for their antifungal action in vitro. The isolates were divided into three groups: T. asperellum, T. virens and T. harzianum. A dual culture assay and a culture filtrate assay against 6 phytopathogens revealed that 9 of the 19 isolates showed significant antifungal activities. The isolate T. harzianum TR05 showed the highest inhibition against Fusarium oxysporum, Rhizoctonia solani, Fusarium circinatum and Phomopsis vexans, followed by T. asperellum TR08 and T. virens TR06. TR08 had the highest inhibition against Sclerotium rolfsii and Pythium aphanidermatum, followed by TR05 and TR06. These findings were in agreement with their activities of extracellular hydrolytic enzymes, including chitinase, β-1,3-glucanase, and proteinase. Our results suggest that isolates TR05, TR06 and TR08 have the potential to be effective biocontrol agents against the phytopathogenic fungi.

DOI： 10.1080/03235408.2016.1147121

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Biological control, especially with Bacillus-based biocontrol agents, offers an attractive alternative to synthetic pesticides for sustainable management of white mold disease caused by Sclerotinia sclerotiorum. In this study, eight effective Bacillus isolates were isolated from rhizospheric soil samples as potential bacterial biocontrol agents. Cultural, biochemical, and molecular analyses of 16S rDNA and gyrase subunit A (gyrA) confirmed that all isolates were identified as Bacillus amyloliquefaciens subsp. plantarum. The production of hydrolytic enzymes and the plant growth-promotional attributes of these isolates confirmed their multifaceted potential. Molecular analysis of the eight biosynthetic genes, which are related to antibiotic properties of bacilli, revealed that all of the isolates possess five genes: bacA for bacilysin, dfnM for difficidin, fenA for fengycin, ituA for iturin, and sfp for surfactin. The Bacillus isolates inhibited mycelial growth and suppressed formation of sclerotia during an in vitro test against S. sclerotiorum. Deformities and cell-wall lysis of mycelia, abnormalities of apothecia, and germination failure of ascospores through interaction with the Bacillus isolates were observed with light and scanning electron microscopes, suggesting that they have high antagonistic effects against S. sclerotiorum. Seed bacterization with the Bacillus isolates protected mustard seedlings in vitro up to 98 % against S. sclerotiorum. In a pot experiment, damages of mustard plants against the pathogen decreased up to 90 % after foliar spray of the Bacillus isolates. In addition, the isolates increased seed germination and accelerated seedling vigor of mustard, suggesting that they have plant growth-promoting functions.

DOI： 10.1007/s13313-016-0397-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

A minimal amount of information is currently available concerning arbuscular mycorrhizal (AM) fungal associations with crops in semi-arid zones on Leptosols in Turkey. Therefore, using molecular ecological techniques, we studied the effects of different management practices (without fertilization, chemical fertilization, farmyard manure, and plant compost amendments) on AM fungal communities associated with wheat roots. Experiments were conducted in a field established in 1996 in southern Mediterranean Turkey where soil productivity is low owing to unfavorable climatic effects and soil characteristics. We determined 201 partial sequences of AM fungal nuclear ribosomal large subunit genes. The higher AM fungal richness was found in the control treatment without fertilization and plant compost treatments compared with the chemical fertilization and farmyard manure treatments. Clones related to Rhizophagus were found in all treatments and accounted for 37% of the total AM fungal clones, whereas those of Funneliformis were dominant under chemical fertilization. Redundancy analysis based on the frequency of operational taxonomic units revealed that AM fungal communities were divided into three groups, namely, the control treatment, the chemical fertilization treatment, and the organic treatments (farmyard manure and plant compost treatments). Although different organic amendments supported relatively similar AM fungal communities, plant compost induced higher AM fungal richness than farmyard manure fertilization.

DOI： 10.1080/15324982.2016.1177749

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s13314-014-0155-9

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Language：Japanese   Publishing type：Research paper (scientific journal)  

CiNii Article

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Radioisotope Association  

<i>After the Fukushima Dai‐ichi Nuclear Power Plant accident in March 2011, contamination of mulberry-leaf tea with over 100</i>Bq kg^－1 ¹³⁷Cs<i> was found. We therefore investigated </i>¹³⁷Cs<i> distribution in mulberry trees(Morus alba) and soil in Nihonmatsu City from 2012. As a result, mulberry leaves near the end of branches(0 - 30</i>cm<i>), which are usually used as edible leaves, were shown to contain higher </i>¹³⁷Cs<i> concentration than the others. Trunk showed highest </i>¹³⁷Cs<i> concentration among the plant parts of mulberry investigated, while root </i>¹³⁷Cs<i> concentration was relatively low. Autoradiographic studies for leaf, bark and cross-sectional trunk suggest that radioactive substances were deposited onto bark and leaf radioactive contamination could be due to translocation of </i>¹³⁷Cs<i> from trunk. Spray application of 0.5</i>% KH₂PO₄<i> solution onto trunk surface significantly reduced </i>¹³⁷Cs<i> concentration in edible leaves emerged about one month after the application. However, the effect was limited and insufficient to solve the problem of radioactive contamination in edible mulberry leaves.</i>

DOI： 10.3769/radioisotopes.64.613

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：EDIZIONI ETS  

DOI： 10.4454/JPP.V97I2.046

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Diphenylarsinic acid (DPAA) is often found as a toxic intermediate metabolite of diphenylchloroarsine or diphenylcyanoarsine that were produced as chemical warfare agents and were buried in soil after the World Wars. In our previous study Guan et al. (J Hazard Mater 241-242:355-362, 2012), after application of sulfate and carbon sources, anaerobic transformation of DPAA in soil was enhanced with the production of diphenylthioarsinic acid (DPTAA) as a main metabolite. This study aimed to isolate and characterize anaerobic soil microorganisms responsible for the metabolism of DPAA. First, we obtained four microbial consortia capable of transforming DPAA to DPTAA at a high transformation rate of more than 80 % after 4 weeks of incubation. Sequencing for the bacterial 16S rRNA gene clone libraries constructed from the consortia revealed that all the positive consortia contained Desulfotomaculum acetoxidans species. In contrast, the absence of dissimilatory sulfite reductase gene (dsrAB) which is unique to sulfate-reducing bacteria was confirmed in the negative consortia showing no DPAA reduction. Finally, strain DEA14 showing transformation of DPAA to DPTAA was isolated from one of the positive consortia. The isolate was assigned to D. acetoxidans based on the partial 16S rDNA sequence analysis. Thionation of DPAA was also carried out in a pure culture of a known sulfate-reducing bacterial strain, Desulfovibrio aerotolerans JCM 12613(T). These facts indicate that sulfate-reducing bacteria are microorganisms responsible for the transformation of DPAA to DPTAA under anaerobic conditions.

DOI： 10.1007/s10532-014-9713-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Kluwer Academic Publishers  

Symptoms of white mould were first observed on jackfruit (Artocarpus heterophyllus) in Rangpur, Bangladesh, during February 2012. Fluffy, white mycelia developed on the fruit surface, along with large irregular black sclerotia. Morphological characteristics and the internal transcribed spacer sequences of ribosomal DNA identified the fungus as Sclerotinia sclerotiorum.

DOI： 10.1007/s13314-014-0155-9

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：日本土壌微生物学会  

DOI： 10.18946/jssm.69.2_128_2

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：日本土壌微生物学会  

DOI： 10.18946/jssm.69.2_125_2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Little is known about the distribution of arbuscular mycorrhizal fungi (AMF, phylum Glomeromycota) in the Turkish arable soils. In this study, we investigated AM fungal phylotype composition in the roots of 13 different plant samples from one site each of the East Black Sea, Mediterranean, and Central Anatolian regions of Turkey. Fifty-seven distinguished operational taxonomic units at 97% nucleotide sequence identity were recorded among 424 partial sequences of the nuclear ribosomal large subunit (LSU) RNA genes determined. Most of the new sequences were clustered within 10 well-resolved phyloclades of the order Glomerales. About half of the newly determined sequences lacked similar sequences in the public databases. In particular, all sequences from Camellia sinensis collected in the East Black Sea region had only 83-97% sequence similarity to known AMF species. The findings suggest that novel and endemic AMF species may exist in Turkish agricultural soils. The AM fungal community composition in the East Black Sea region was relatively simple and completely differed from those in the other two regions, presumably due to the low soil pH and host specificity. The AM fungal community compositions of the Mediterranean and Central Anatolian samples were broadly similar; however, some sequences related to Rhizophagus were found only in the Mediterranean samples. This reflects the trend that more diverse AM fungal communities are established in the Mediterranean region than the Central Anatolian region.

DOI： 10.1080/00380768.2014.890916

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

There is concern that radiocesium deposited in the environment after the accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011 will migrate to paddy fields through hydrological pathways and cause serious and long-lasting damage to the agricultural activities. This study was conducted in the Towa region of Nihonmatsu in the northern part of Fukushima Prefecture, Japan, (1) to quantify Cs-137 in stream water used to irrigate paddy fields by separating the dissolved and particulate components in water samples and then fractionating the particulate components bonded in different ways using a sequential extraction procedure, and (2) to determine the amounts of radiocesium newly added to paddy fields in irrigation water relative to the amounts of radiocesium already present in the fields from the deposition of atmospheric fallout immediately after the FDNPP accident. Three catchments were studied, and the Cs-137 activity concentrations in stream water samples were 79-198 mBq L-1 under stable runoff conditions and 702-13,400 Bq L-1 under storm runoff conditions. The residual fraction (F4, considered to be non-bioavailable) was dominant, accounting for 59.5-82.6% of the total 137Cs activity under stable runoff conditions and 69.4-95.1% under storm runoff conditions. The 137Cs newly added to paddy fields in irrigation water only contributed 0.03-0.05% of the amount already present in the soil (201-348 kBq m(-2)). This indicates that the Cs-137 inflow load in irrigation water is negligible compared with that already in the soil. However, the contribution from the potentially bioavailable fractions (F1 + F2 + F3) was one order of magnitude larger, accounting for 0.20-0.59%. The increase in the dissolved and soluble radiocesium fraction (F1) was especially large (3.0% to infinity), suggesting that radiocesium migration in irrigation water is increasing the accumulation of radiocesium in rice. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.scitotenv.2014.01.129

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Diphenylarsinic acid (DPAA) is a toxic phenylarsenical compound often found around sites contaminated with phenylarsenic chemical warfare agents, diphenylcyanoarsine or diphenylchloroarsine, which were buried in soil after the World Wars. This research concerns the elucidation of the chemical structure of an arsenic metabolite transformed from DPAA under anaerobic sulfate-reducing soil conditions. In LC/ICP-MS analysis, the retention time of the metabolite was identical to that of a major phenylarsenical compound synthesized by chemical reaction of DPAA and hydrogen sulfide. Moreover the mass spectra for the two compounds measured using LC/TOF-MS were similar. Subsequent high resolution mass spectral analysis indicated that two major ions at m/z 261 and 279, observed on both mass spectra, were attributable to C12H10AsS and C12H12AsSO, respectively. These findings strongly suggest that the latter ion is the molecular-related ion ([M+H]+) of diphenylthioarsinic acid (DPTA
(C6H5)2AsS(OH)) and the former ion is its dehydrated fragment. Thus, our results reveal that DPAA can be transformed to DPTA, as a major metabolite, under sulfate-reducing soil conditions. Moreover, formation of diphenyldithioarsinic acid and subsequent dimerization were predicted by the chemical reaction analysis of DPAA with hydrogen sulfide. This is the first report to elucidate the occurrence of DPAA-thionation in an anaerobic soil. © 2013 Elsevier B.V.

DOI： 10.1016/j.jhazmat.2013.08.020

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

DPAA is often found as one of the major degradation products in soil and groundwater contaminated with diphenylcyanoarsine or diphenylchloroarsine. These compounds were produced mainly during the World Wars as chemical warfare agents. This study investigated the effect of DPAA contamination on soil bacterial and archaeal community structures under anaerobic conditions in a model experiment using 16S rRNA targeted PCR-DGGE fingerprinting of DNA extracted from the contaminated soil. DPAA decreased in anaerobically incubated soil cultures due to microbiological activity. Addition of rice straw partially enhanced the extent of DPAA degradation. Inorganic arsenic acid, PM, and an unknown arsenical species were detected as degradation products using LC-ICPMS. PCR-DGGE fingerprinting for bacterial community analysis revealed that anaerobic bacterial and archaeal species, including Clostridium and Methanosarcina, became abundant in the incubated soil within a week. In the soil cultures incubated with DPAA, while a few bacterial bands found on the DGGE gels disappeared or became weaker, most of the bands showed no significant changes. Addition of DPAA had no significant effect on archaeal communities. These findings suggest that, even though DPAA may have a direct effect on some abundant bacterial species, overall bacterial and archaeal community structures under the anaerobic soil conditions tended to be stable regardless of DPAA contamination. (c) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.geoderma.2012.12.007

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society of Irrigation, Drainage and Rural Engineering  

Radiocesium (Cs) decontamination of land has been required as one of the restoration measures after the Tohoku-Pacific Ocean Earthquake disaster. The Ministry of Agriculture, Forestry and Fisheries (MAFF) of Japan plans to carry out decontamination measures of farmland in response to the situation of land contamination. However, in order to achieve effective restoration, strategic and comprehensive measures including land readjustment are necessary. In this paper, we examined characteristics of Cs contamination from the view of the spatial extent contamination, land use, land improvement and working environment, and made the following proposals: (1) Implementation of Cs decontamination works ought to follow the principle of &ldquo;containment&rdquo;, &ldquo;isolation&rdquo;, and &ldquo;securing long-term safety&rdquo; of Cs, and improve both production environment and working environment of farmlands. (2) Strategic approaches should be carried out in a comprehensive and unified manner for the effective implementation of Cs decontamination.

DOI： 10.11408/jsidre.80.555

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Diphenylarsinic acid (DPAA) is known to be the major contaminant in soils where diphenylchloroarsine and diphenylcyanoarsine were abandoned after World Wars I and II. In this study, experimental model studies were performed to elucidate key factors regulating the transformation of DPAA under anaerobic soil conditions. The elimination of DPAA in Gleysol soils (Qiqihar and Shindori soils) was more rapid than in Mollisol and Regosol soils (Heihe and lkarashi soils, respectively) during a 5-week incubation. No clear relationship between decreasing rates of DPAA concentrations and soil Eh values was found. The Ikarashi soil showed the slowest decrease in DPAA concentrations among the four soils, but the transformation of DPAA was notably enhanced by addition of exogenous sulfate together with acetate, cellulose or rice straw. Addition of molybdate, a specific inhibitor of sulfate reduction, resulted in the stagnation of DPAA transformation, suggesting that indigenous sulfate reducers play a role in DPAA transformation under anaerobic conditions. Arsenate, phenylarsonic acid, phenylmethylarsinic acid, diphenylmethylarsine oxide and three unknown compounds were detected as metabolites of DPAA. This is the first study to reveal enhancement of DPAA transformation under sulfate-reducing conditions. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jhazmat.2012.09.054

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A magnitude 9.0 earthquake and subsequent large tsunami hit the northeastern coast of Japan on March 11, 2011. This resulted in serious damage to the reactors of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), operated by the Tokyo Electric Power Company. Large amounts of radionuclides were released from the FDNPP, a proportion of which were deposited onto the ground. In this study, we investigated soil radiocesium contamination of rice fields in Aga and Minamiuonuma, Niigata, similar to 130 and 200 km away from the FDNPP, respectively, as Niigata is one of the largest rice growing regions in Japan. Soil samples were collected from the plow layer of five rice fields in August and September, 5-6 months after the FDNPP accident. Results showed that radiocesium concentrations (the sum of Cs-134 and Cs-137) in the rice soil samples were similar to 300 Bq (kg dry soil)(-1). All samples contained a Cs-134/Cs-137 activity ratio of 0.68-0.96 after correction to March 11, 2011, showing that the radiocesium released from the FDNPP were deposited on these areas. Although the rice fields had been disturbed by farming processes after the FDNPP accident, the depth distribution of radiocesium concentrations in the plow layers showed higher concentrations in the upper soil layers. This suggests that spring tillage, flooding and puddling performed before rice transplantation may not disperse radiocesium deposited on the surface through the whole plow layer. In addition, the planar distribution of radiocesium concentrations was examined near the water inlet in one of the rice fields. Highest activities were found aligned with the direction of irrigation water discharge, indicating that radioactivity levels in rice fields may be elevated by an influx of additional radionuclides, probably in irrigation water, during farming. (c) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.scitotenv.2012.05.032

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Melamine has recently been recognized as a food contaminant with adverse human health effects. Melamine contamination in some crops arises from soil and water pollution from various causes. To remove melamine from the polluted environment, a novel bacterium, Nocardioides sp. strain ATD6, capable of degrading melamine was enriched and isolated from a paddy soil sample. The enrichment culture was performed by the soil-charcoal perfusion method in the presence of triazine-degrading bacteria previously obtained. Strain ATD6 degraded melamine and accumulated cyanuric acid and ammonium, via the intermediates ammeline and ammelide. No gene known to encode for triazine-degrading enzymes was detected in strain ATD6. A mixed culture of strain ATD6 and a simazine-degrading Methyloversatilis sp. strain CDB21 completely degraded melamine, but the degradation rate of cyanuric acid was slow. The degradation of melamine and its catabolites by the mixed culture was greatly enhanced by including Bradyrhizobium japonicum strain CSB1 in the inoculum and adding ethanol to the culture medium. The melamine-degrading consortium consisting of strains ATD6, CDB21, and CSB1 appears to be potentially safer than other known melamine-degrading bacteria for the bioremediation of farmland and other contaminated sites, as no known pathogens were included in the consortium.

DOI： 10.1007/s00253-011-3673-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Microorganisms capable of degrading diphenylarsinic acid (DPAA) were enriched from contaminated soil using the soil-charcoal perfusion method. Two novel bacterial strains, L2406 and L2413, that can degrade DPAA in a mineral salt medium supplemented with DPAA as the sole carbon source were isolated. Based on comparative morphology, physiology, and comparison of the 16S rRNA gene sequences, both were presumed to be species closely related to Ensifer adhaerens. As the metabolites, phenylarsonic acid (PAA) was determined by liquid chromatography-mass spectrometry analysis as well as three unknown peaks all of whose molecular weights were estimated to be 278. The increase of m/z = 16 from DPAA in the unknowns suggests monohydroxylation of DPAA at the 2-, 3- and 4-positions. The ability of strains L2406 and L2413 to degrade DPAA was suppressed in iron insufficient conditions, e.g. less than 7.2 mu M iron in the culture medium. These facts strongly suggest the following hypothesis: Monooxygenase works at the initial degradation step of DPAA degradation by the isolates; and direct hydrolysis from DPAA to PAA is not likely to occur. In addition, release of arsenic acid from PAA by strain L2406 was confirmed by liquid chromatography-inductively coupled plasma mass spectrometry. From these results, strain L2406 was considered to be capable of degrading DPAA to arsenic acid via PAA when DPAA was supplied as the sole carbon source.

DOI： 10.1007/s10532-009-9318-3

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SOC MICROBIOLOGY  

A novel aerobic pentachloronitrobenzene-degrading bacterium, Nocardioides sp. strain PD653, was isolated from an enrichment culture in a soil-charcoal perfusion system. The bacterium also degraded hexachlorobenzene, a highly recalcitrant environmental pollutant, accompanying the generation of chloride ions. Liberation of (14)CO(2) from [U-ring-(14)C] hexachlorobenzene was detected in a culture of the bacterium and indicates that strain PD653 is able to mineralize hexachlorobenzene under aerobic conditions. The metabolic pathway of hexachlorobenzene is initiated by oxidative dechlorination to produce pentachlorophenol. As further intermediate metabolites, tetrachlorohydroquinone and 2,6-dichlorohydroquinone have been detected. Strain PD653 is the first naturally occurring aerobic bacteria capable of mineralizing hexachlorobenzene.

DOI： 10.1128/AEM.02329-08

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Nocardioides sp. strain MTD22 degraded atrazine, ametryn and atraton, as did Arthrobacter aurescens strain TC1 and Nocardioides sp. strain C190. These strains contain trzN, a gene coding for TrzN, triazine hydrolase showing a broad substrate range. However, Nocardioides sp. strain AN3 degraded only atrazine despite containing trzN. These differences in s-triazine degradation are presumed to be due to differences in the amino acid sequences of TrzNs. Consequently, 1371 nucleotides of the trzN coding sequences of strains AN3 and MTD22 were determined. Comparisons of the amino acid sequences of TrzNs indicated that three residues of strain AN3 (Thr(214), His(215) and Gln(241)) were distinct from those of the other three strains (Pro(214), Tyr(215) and Glu(241)). To confirm the relationships between these amino acid sequences and the substrate specificities of TrzNs, wild and chimera trzN genes were constructed and expressed in Escherichia coli cells. Cells expressing wild MTD22 trzN (Pro(214)Tyr(215)Glu(241)) and chimera AN3-MTD22 trzN (Thr(214)His(215)Glu(241)) degraded all s-triazines, but the degradation rate was markedly decreased in AN3-MTD22 trzN. Wild AN3 trzN (Thr(214)His(215)Gln(241)) and chimera MTD22-AN3 trzN (Pro(214)Tyr(215)Gln(241)) degraded only atrazine. These results suggest that the substitution of Glu(241) for Gln(241) significantly decreases enzyme affinity for ametryn and atraton.

DOI： 10.1111/j.1574-6968.2008.01271.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PESTICIDE SCI SOC JAPAN  

A special type of charcoal, Charcoal A 100, was enriched with a newly developed bacterial consortium using a perfusion method. The bacterial consortium consisted of a methylthio-s-triazine-degrading bacterium (Rhodococcus sp. FJIII7YT) and the chloro-s-triazine-degrading bacterial consortium CD7 (containing Bradyrhizobium japonicam CSBI, Arthrobacter sp. CD7w and beta-Proteobacteria CDB21). Enriched charcoal was capable of degrading chloro-s-triazines (simazine and atrazine) and methylthio-s-triaiznes (simazine and atrazine) and methylthio-s-triazines (simetryn and dimethametryn) simultaneously in sulfur-free medium. Almost complete degradation was observed after 4-day cultivation of chloro-s-triazines and 9-day cultivation of methylthio-s-triazines. These triazines were mineralized via their 2-hydroxy analogues.

DOI： 10.1584/jpestics.G08-08

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society of Soil Microbiology  

Methanogenesis in irrigated rice fields is carried out by methanogenic archaea under strictly anaerobic conditions. In the present study, the effect of rice straw on methanogenesis in surface layers of paddy soil was investigated in a pot experiment with surface application of rice straw. Rice straw application led to a significant development of reduced conditions in the surface soil, and markedly increased methane (CH_4) emissions. Potential methanogenic activity in the straw residues and the soil layer immediately under the residues (0〜1 cm depth) was considerably promoted, while that in the deeper soil layers (4〜6 cm depth) was not affected by the residues of rice straw. These results indicate that the increased CH_4 emission in the treatment with surface application of rice straw was due to the activation of methanogenesis in the vicinity of the residues. Consequently, in the present study, it was demonstrated that rice straw application enhanced methanogenesis even in the surface layers of paddy soil, which are generally considered to be oxic layers.

DOI： 10.18946/jssm.61.1_17

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Other Link： http://hdl.handle.net/10191/24984

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

A moderately persistent herbicide, simazine, has been used globally and detected as a contaminant in soil and water. The authors have isolated a simazine-degrading bacterium from a simazine-degrading bacterial consortium that was enriched using charcoal as a microhabitat. The isolate, strain CDB21, was gram-negative, rod-shaped (0.5-0.6 mu m x 1.0-1.2 mu m) and motile by means of a single polar flagellum. Based on 16S rRNA sequence analysis, strain CDB21 was identified as a novel beta-proteobacterium exhibiting 100% sequence identity with the uncultured bacterium HOClCi25 (GenBank accession number AY328574). PCR using primers that were specific for the genes of the atrazine-degrading enzymes (atzABCDEF) of Pseudomonas sp. strain ADP showed that strain CDB21 also possessed the entire set of genes of these enzymes. Nucleotide sequences of the atzCDEF genes of strain CDB21 were 100% identical to those of Pseudomonas sp. strain ADP. Sequence identity of the atzA genes between these bacteria was 99.7%. The 398-nucleotide upstream fragment of the atzB gene of strain CDB21 was 100% identical to ORF30 of Pseudomonas sp. strain ADP, and the 1526-nucleotide downstream fragment showed 99.8% sequence similarity to the atzB gene of the pseudomonad. (c) 2007 Society of Chemical Industry.

DOI： 10.1002/ps.1334

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

A novel bacterial strain FJ1117YT was isolated from an enrichment culture with the herbicide simetryn. The isolate was capable of degrading the herbicide supplied as the sole sulfur source in an aquatic batch culture. The strain FJ1117YT was identified as that belonging to Rhodococcus sp. on the basis of comparative morphology, physiological characteristics and comparison of the 16S rRNA gene sequence. The biodegradation pathway of simetryn was established by isolating the methylsulfinyl analogue as the first metabolite and by identification of the methylsulfonyl intermediate and the hydroxy analogue by liquid chromatography-mass spectrometry (LC-MS) and/or nuclear magnetic resonance (NMR) analysis. The results indicate that the methylthio group was progressively oxidised and hydrolysed by the strain FJ1117YT. The same strain is also able to metabolise other methylthio-s-triazines such as ametryn, desmetryn, dimethametryn and prometryn through similar pathways. (c) 2007 Society of Chemical Industry.

DOI： 10.1002/ps.1331

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society of Soil Science and Plant Nutrition  

DOI： 10.20710/dojo.78.1_89

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Other Link： http://agriknowledge.affrc.go.jp/RN/2010734296

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

It is known that methylthio-s-triazines can be transformed to the corresponding 2-hydroxy derivatives through sulfoxides and sulfones in aerobic and flooded soil; however, production of sulfoxides and/or sulfones from methylthio-s-triazines by isolated s-triazine-degrading bacteria has not been reported yet. In the present study, a new bacterial strain, JUN7, was obtained from Japanese soil; the bacterium is capable of transforming simetryn to 2-methylsulfinyl 4,6-bis(ethylamino)-s-triazine (sulfoxide simetryn) and 2-hydroxy-4,6-bis(ethylamino)-s-triazine (2-hydroxy simetryn) in a Luria-Bertani (LB) medium. This is the first isolation of the specific microorganism that mediates sulfur oxidation of methylthio-s-triazines, as far as we know. Strain JUN7 could decrease other methylthio-s-triazines such as dimethametryn and prometryn, but not chlorinated s-triazines (atrazine, simazine, and terbuthylazine) and methoxy-s-triazine (atraton) in 1/10 LB medium. Strain JUN7 did not possessed gene atzA or trzN encoding triazine-degrading enzymes, suggesting that the strain may have another metabolic system. Characterizations of strain JUN7 based on comparative morphology, physiological classification, and comparison of the partial 16S rRNA sequence indicated that it is assigned as a Bacillus cereus species. (c) 2006 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.soilbio.2006.03.018

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Three strains-Nocardioides sp. MFC-A, Rhodococcus rhodochrous MFC-B, and Stenotrophomonas sp. MFC-C-were newly isolated from rice soil or bark compost as microorganisms capable of cometabolically degrading mefenacet (2-benzothiazol-2-yloxy-N-methylacetanilide). Several other species belonging to the genera Nocardioides, Rhodococcus, and Stenotrophomonas were also capable of degrading mefenacet, suggesting that the ability is not specific to these isolates, but common at least in these genera. N-methylaniline and 2-benzothiazoloxy acetic acid were identified as the metabolites by liquid chromatography-mass spectrometry. Besides mefenacet, the isolates could degrade one or more other amide pesticides, such as flutolanil, mepronil, metolachlor, and pretilachlor. These results indicate that the strains Nocardioides sp. MFC-A, Rhodococcus rhodochrous MFC-B, and Stenotrophomonas sp. MFC-C degrade mefenacet via hydrolysis of the amide bond, but their substrate specificities differ. (c) 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.soilbio.2005.04.015

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC SOIL SCIENCE PLANT NUTRITION  

Phototrophic purple bacteria (PPB) are one group of dinitrogen (N-2)-fixing bacteria often found in the anoxic and photic zone of paddy soil. In the present study, the effects of inoculation of PPB on grain yield of rice and changes in their populations and nitrogenase activity were investigated with and without surface application of rice straw in a pot experiment. As an inoculant, Rhodopseudomonas palustris strain KN122 isolated from a paddy soil was selected, and the cell suspension was inoculated into the floodwater once or three times during the cultivation. As a result, the inoculation of PPB increased the grain yield of rice. Compared to the control, the grain yield was 9% higher in the inoculated plot without rice straw application. The treatment was more effective in combination with rice straw application. In the plots where PPB were inoculated with rice straw, grain yields were 21% (single inoculation) and 29% (triple inoculation) higher. Populations of PPB in the plots without rice straw application significantly increased by the inoculation, unlike those in the plots with rice straw application, except for the bulk soil. Phototrophic and heterotrophic nitrogenase activities (acetylene-reducing activity) associated with the soils or residues of the rice straw were not affected by PPB inoculation throughout the experiment. This indicates that the inoculation of PPB into floodwater may not be effective for enhancing N2 fixation in paddy soils and that the beneficial effect of PPB inoculation on the grain yield of rice may be due to unidentified functions of PPB other than biological N-2 fixation.

DOI： 10.1111/j.1747-0765.2005.tb00041.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

A pot experiment was conducted to investigate the influences of indigenous phototrophs on methane (CH4) emissions from a paddy soil where rice straw was incorporated or was surface-applied. During the cultivation, half of the pots were covered with aluminum foil, except for the minimum space for rice plants, to prevent ambient light reaching the floodwater or the soil surface. Growth of oxygen-producing phototrophs was hardly observed in the unilluminated plots, whereas intensive growth of algae, duckweed and hydrophytes was found in the illuminated ones. Plant growth was not affected by the different treatments. Seasonal changes in CH4 emission determined by a closed chamber method indicated that illumination had no or only minor effects on CH4 emissions when rice straw was incorporated or was not applied, but significantly reduced CH4 emissions when rice straw was surface-applied. Methanogenesis occurring in the soil-floodwater interface was further investigated in two lab-scale model experiments measuring methanogenic activity. As a result, more activated methanogenesis was found in the surface-applied rice straw and the soil around the straw compared with the soil incubated without rice straw. The magnitude of the methanogenic activity in the rice straw incubated under illuminated conditions was significantly lower than that incubated in the dark. Consequently, this study demonstrates that methanogenesis in paddy soil occurs even in the soil-floodwater interface if plant residues like rice straw exist, and such methanogenesis is likely to be suppressed by growth of indigenous phototrophs under illumination.

DOI： 10.1007/s00374-004-0793-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC SOIL SCIENCE PLANT NUTRITION  

Phototrophic purple bacteria (PPB) were isolated from a Japanese paddy soil and their microbiological characteristics were then analyzed based on comparative morphology, chemotaxonomy, and comparison of 16S rDNA sequences. As a result, 18 strains of PPB were isolated, of which 17 strains were identified as Rhodopseudomonas palustris strains. The other was as a Rubrivivax gelatinosus strain. All the isolates showed a positive reaction in the acetylene reduction assay in the N-reduced medium. Effects of inoculation of the isolates into the soil slurries on soil acetylene-reducing activity (ARA) and methane (CH4) emissions from the slurries were examined using washed cells. The inoculated slurries showed a positive ARA reaction after 10-d incubation under illumination, unlike the control. CH4 emissions from the soil slurries 10-d after the inoculation of the isolates identified as Rps. palustris strains were significantly lower (44-62%) than those from the slurries without inoculants. These results suggest that PPB contribute to the enhancement of soil nitrogen fixation and mitigation of CH4, emissions from paddy soils.

DOI： 10.1080/00380768.2003.10410041

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER-VERLAG  

Interactions between sulfate reduction (SR) and phototrophic nitrogenase activities were investigated in rice soil slurries mixed with rice straw. Activation of SR by adding exogenous sulfate suppressed acetylene-reducing activity (ARA) of the slurries, which was associated with phototrophic purple bacteria (PB) enumerated to 10(8)-10(9) MPN g(-1) dry weight (dw) soil. Adding 5 mM sodium molybdate, an inhibitor of SR, markedly increased ARA. However, in the slurries receiving both molybdate and exogenous sulfate, the effects declined simultaneously with partial recovery of SR. These results indicate outcompetition of sulfate-reducing bacteria (SRB) with PB in rice soil, when sulfate concentrations are high enough to support SR. The increasing effects of molybdate on ARA continued during the incubation in the sulfate-depleted condition, probably because of absence of SR and toxicity of molybdate to methanogenesis. Accordingly, stopping activities of the competitive microorganisms may be efficient to increase N-2 fixation in rice soil.

DOI： 10.1007/s002840010236

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The interaction between phototrophic dinitrogen fixers and methanogens was examined in soil slurries amended with rice straw using 2-bromoethanesulfonic acid (BES), a specific methanogenic inhibitor. Slurries incubated in light increased phototrophic nitrogenase activity (acetylene reducing activity), and showed growth of phototrophic purple bacteria and reduction of CH4 emission, indicating outcompetition of purple bacteria with methanogens in photic zones. Adding BES effectively inhibited methane production and markedly increased phototrophic acetylene reducing activity accompanied with acetate accumulation, but did not affect populations of purple bacteria in the slurries. More acetate accumulated in the inhibited slurries incubated in dark. We suggest that increased availability of organic substrates for purple bacteria after slopping methanogenic consumption by BES caused the increased phototrophic acetylene reducing activity. These results indicate that, after purple bacteria glow enough, performance of their N-2 fixation may be limited by substrate availability, which methanogenesis may profoundly influence. (C) 2001 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0168-6496(01)00095-2

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (other)   Publisher：新潟県土壌肥料懇話会  

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Language：English   Publishing type：Article, review, commentary, editorial, etc. (bulletin of university, research institution)   Publisher：新潟大学農学部  

Pseudomonas sp. strain ADP has been studied most extensively. Dechlorination of the s-triazine ring by the strain is mediated by atrazine chlorohydrolase (AtzA) and the subsequent degradation is associated with AtzBCDEF. A novel simazine-degrading β-proteobacterium strain CDB21 isolated by the author's group also possessed entire-set of genes of these enzymes (atzABCDEF). However, while atzA is located between ORF30 and atzB in strain ADP, ORF30 fused with atzB in strain CDB21. This indicates that localization of atzA in CDB21 differs from that in the pseudomonad, meaning that genetic variations regarding the degradation genes exist among microorganisms capable of degrading chloro-s-triazines. It is known that methylthio-s-triazines can be transformed to the corresponding hydroxy analogues via sulfur oxidation in aerobic and flooded soil. Recently, two types of bacteria that engage the process were isolated. One is Bacillus cereus strain JUN7 that can degrade methylthio-s-triazines to give the methylsulfinyl and hydroxy analogues under nutrient-rich conditions such as those with the Luria-Bertani medium. The other is Rhodococcus sp. strain FJ1117YT that is able to degrade methylthios-triazines supplied as the sole sulfur source. These strains were unable to degrade chloro-s-triazines. No gene encoding AtzA or TrzN (triazine hydrolase) was found in these strains, suggesting that they may have another metabolic system. Using a special charcoal material enriched with a simazine-degrading bacterial consortium involving strain CDB21, in situ bioremediation study was conducted in a golf course, where simazine is routinely applied for preservation of turf. As a result, the material was effective for preventing penetration of simazine into subsoils and aquatic environments nearby for approximately 2 years. This result suggests that use of adequate habitat materials is preferable to maintain population and activity of inoculant bacteria applied to soil environment.

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Other Link： http://agriknowledge.affrc.go.jp/RN/2010742733

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher：Environmental Communications, Co., Ltd.  

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Language：English   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Poster presentation  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Poster presentation  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Poster presentation  

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Language：English   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Poster presentation  

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Language：English   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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