2000 Fiscal Year Final Research Report Summary
Studies on chemolithotrophic ammonia-oxidizing bacteria producing nitrous oxide in crop rhizosphere
Project/Area Number |
10660061
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Research Category |
Grant-in-Aid for Scientific Research (C)
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Allocation Type | Single-year Grants |
Section | 一般 |
Research Field |
Plant nutrition/Soil science
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Research Institution | Yamaguchi University (1999-2000) Kagawa University (1998) |
Principal Investigator |
YOKOYAMA Kazuhira Faculty of Agriculture, Yamaguchi University, Associate Professor, 農学部, 助教授 (10230658)
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Project Period (FY) |
1998 – 2000
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Keywords | Ammonia-oxidizing bacteria / Nitrous oxide / Rhizosphere |
Research Abstract |
I found that there was no apparent inhibition by spinach roots on the activity and population of chemolithotrophic ammonia-oxidizing bacteria (AOB) in rhizosphere soil with the relatively higher concentration of ammoniumu ion. MPN-nested PCR and specific probings revealed that Nitrosospira spp. was a cosmoporitan throughout rhizosphere and non-rhizosphere soil while Nitrosomonas spp. was detected inconsistently. A half of the bacteria enumerated remained being unidentified by oligonucleotide probes for Nitrosospira spp., Nitrosolobus multiformis, Nitrosomonas europaea and Nitrosomonas eutropha. The production of nitrous oxide was not detected during the assay by the chlorite-inhibition method, suggesting that these bacteria did not produce a significant amount of the gas under aerobic conditions. The effect of organic compounds in anabolisms on the nitrite production by N.europaea was tested. Citrate inhibited the nitrite production by N.europaea when the activity was very low. With the
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increase in the cell activity, its performance turned stimulating. The cells of N.europaea in a logarismic phase were not affected by the addition of organic compounds. These facts suggested that some of organic compounds would effect the growth of AOB in rhizosphere. I tested the specific fluorescent staining of active ammonia monooxygenase (AMO) by fluorescein thiocarbamoylpropargylamine (FTCP), first designed by McTavish et al.(1993). FTCP inhibited the nitrite production by Nitrosomonas sp.TK794. After washing, the FTCP-treated cells started to produce nitrite in a FTCP-free medium. Acetylene-pretreated cells were stained by FTCP.These strongly suggested that FTCP might be a competetive inhibitor rather than the suicide substrate for AMO. I tested the production by the contribution of AOB in nitrous oxide emission from spinach rhizosphere by dimethylether inhibition and a non-destructive methods. 37 days after seeding, the potential of nitrification was higher in the system supplied with the medium containing 9 : 1 and 5 : 5 (NH_4^+ : NO_3^-, in a moler ratio) than 1 : 9. However. AOB were accounted less than 36% of the total emission even in the 9 : 1 treatment. There was no evidence that these bacteria preferentially colonized on root surface. Less
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