Characterization of microbial consortia in paddy rice soil by phospholipidanalysis

Microbial biomass and community structure in paddy rice soil during the veg etation period of rice were estimated by analysis of their phospholipid fat ty acids (PLFA), hydroxy fatty acids of lipo-polysaccharides (LPS-HYFA), an d phospholipid ether lipids (PLEL) directly extracted from the soil. A clea r change in the composition of the community structure at different samplin g periods was observed, indicated by the principal component analysis of th e PLFA. A dramatic decline of ester-linked PLFA was observed in the soil sa mples taken at the second sampling time. In contrast to the ester-linked PL FA, the non-ester-linked PLFA composition did not change. The hydroxy fatty acids of lipopolysaccharides as well as ether lipids decreased consecutive ly during the observation period. Total microbial abundance was estimated t o be (4.1-7.3) x 10(9) cells g(-1) soil (dry weight). About 44% account for aerobic and 32% for facultative anaerobic bacteria, and 24% for archaea, o n average. According to the profile and patterns of PLFA in the soil sample , it may be suggested that the paddy soil at the August sampling period con tained more abundant facultative anaerobic bacteria (ca. 36%) and archaea ( ca. 37%), but the total microbial biomass was significantly lower than in t he remaining sampling periods. As the plant approached maturity, the microb ial community structure in the soil changed to contain more abundant Gram-n egative bacteria and methanotrophs.