2002 Fiscal Year Final Research Report Summary
Augmentation of Nitrite-reducing Capacity of Ruminal Bacteria
| Project/Area Number |
13660273
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Zootechnical science/Grassland science
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| Research Institution | Meiji University |
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Principal Investigator |
HINO Tsuneo Meiji University, School of Agriculture, Professor, 農学部, 教授 (50012050)
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| Project Period (FY) |
2001 – 2002
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| Keywords | Ruminal microbes / Nitrate / nitrite reduction / Methane suppression / Selenomonas ruminantium / Veillonella parvulla / Wolinella succinogenes / Methanogens / Competitive PCR |
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| Research Abstract |
1) Effect of protozoa on nitrate and nitrite reduction
Nitrate reduction rate was higher when protozoa coexisted with bacteria than when only bacteria were grown. The effect of protozoa was greater on nitrite reduction than on nitrate reduction, which resulted in decreased nitrite accumulation. Stimulation of nitrate and nitrite reduction by protozoa was shown to be mainly due to the production of H2 and lactate (electron donors) by protozoa.
2) Effects of energy substrates on nitrate reduction and nitrate reductase in Selenomonas ruminantium
Nitrate reduction rate was parallel to the amount of nitrate reductase (NaR) in cells. The amount of NaR was inversely related to growth rate. Nitrate reduction rate (the amount of NaR) was inversely related to the level of intracellular ATP and the ratio of NADH to NAD^+. Therefore, the synthesis of nitrate reductase may be regulated in response to the sufficiency of energy and electron supply. NaR synthesis was suggested to be enhanced by nitrate.
3) Numbers of nitrate-reducing bacteria in the rumen as estimated by competitive PCR
The cell number of S. ruminantium in the rumen of goats was much larger than Veillonella parvula and Wollinella succinogenes. However, the numbers of the latter two bacteria were increased by feeding a high-nitrate diet.
4) Effect of nitrate and nitrite reduction on the suppression of methanogenesis
The above three bacteria were found to acquire energy by electron transport phosphorylation coupled with nitrate and/or nitrite reduction, and are more tolerant to nitrite toxicity than other ruminal bacteria. Therefore, high-nitrate diets may favors the growth of these bacteria in the rumen. Methane production was markedly reduced by the presence of the three bacteria. Methanogenic bacteria were shown to be more sensitive to nitrite than other bacteria, which may additionally suppress methanoaenesis.
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