Microbial community responsible for the decomposition of rice straw in a paddy field: estimation by phospholipid fatty acid analysis

摘要

To estimate the microbial communities responsible for rice straw decomposition in paddy field, phospholipid fatty acid (PLFA) composition of leaf sheaths and blades was analyzed during the decomposition of both residues under upland conditions after harvest and under flooded conditions at the time of transplanting of rice plants. In addition, rice straw that had been placed in the field under upland conditions (November to April) was taken out in spring, and placed again in the same field under flooded conditions at the time of transplanting. High proportions of the branched-chain PLFAs were observed under flooded conditions (June to September); the proportions of straight mono-unsaturated and straight poly-unsaturated PLFAs were high under upland conditions in the winter season for 4 months. The dominant PLFAs in straight mono-unsaturated, straight poly-unsaturated and branched-chain PLFA groups were 18:1ω9, 18:1ω7 and 16:1ω7c, 18:2ω6c and i15:0, i17:0 and ai15:0, respectively, under both upland and flooded conditions. These findings indicated the important roles of Gram-negative bacteria and fungi under upland conditions and of Gram-positive bacteria and anaerobic Gram-negative bacteria under flooded conditions. Cluster analysis of PLFA composition showed the difference of community structure of microbiota in rice straw between upland and flooded conditions. In addition principal component analysis revealed the difference between leaf sheaths and blades under upland conditions and indicated that the content of straight unsaturated PLFAs (sheaths > blades) characterized their community structures.