123-29 Isolation and Characterization of Bacteria That Efficiently Eliminate Ammonium Nitrate.



Monday, October 17, 2011
Henry Gonzalez Convention Center, Hall C, Street Level

Mitsuaki Ota, Graduate School of Agriculture, Meiji University, Kawasaki, Japan, Shuichiro Murakami, Agricultural Chemistry, School of Agriculture, Meiji University, Kawasaki, Japan and Kosuke Noborio, Agriculture, School of Agriculture, Meiji University, Kawasaki, Japan
Nitrous oxide (N2O) has a 200-300-fold-stronger greenhouse effect than carbon dioxide. N2O is produced in agricultural fields through a denitrification process by microorganisms. In this process, nitrate ion (NO3-) is reduced to nitrogen (N2) through subsequent reductive reactions by denitrifying bacteria under an anaerobic condition. The reduction of N2O to N2, the final step of denitrification is, however, strongly suppressed by oxygen. Because agricultural fields are under aerobic conditions, the large amount of N2O is produced from fertilized NO3-, and account for 52% of man-made N2O. Regarding global climate change, it is important to decrease N2O emission in agricultural fields. To decrease N2O emission, we thought that it could be possible by managing microorganisms with an ability to convert NO3- into N2 or into N-containing organic compounds under aerobic conditions in agricultural fields. We, therefore, attempted to isolate bacteria that were suitable for our purpose. Seventy-seven rhizosphere soil samples were collected from vegetable fields.  Enrichment culture was performed in a screening medium containing 0.1% NH4NO3 and 2% glucose. Finally, four strains (named N-I, N-II, N-III, and N-IV) were selected because of efficient NH4NO3 elimination under an aerobic condition, and identified as Enterobacter cloacae on the basis of morphological, physiological, biochemical, and genetical properties. To identify the products of NH4NO3, total nitrogen of couture (supernatant and strain) was analyzed. The four strains did not denitrify but synthesized other nitrogen compounds and accumulated them in the supernatants.  Although the supernatants contained few amino acids, the acid hydrolysates from the supernatants showed some amino acids by HPLC analysis, suggesting that the nitrogen compounds were similar to peptide. Subsequently, we purified peptide-like compounds and are working on structural analyses for the compounds.
See more from this Division: S03 Soil Biology & Biochemistry
See more from this Session: Microbe, Plant , and Soil Interactions (Includes Graduate Student Poster Competition)