Comparison of phospholipid fatty acid composition in percolating water, floodwater, and the plow layer soil during the rice cultivation period in a Japanese paddy field

Abstract

The composition of phospholipid fatty acids (PLFAs) in the percolating water (PW), the floodwater (FW), and the plow layer soil (PLS) in a paddy field was compared during the period of rice cultivation. The amounts of PLFAs in PW, FW, and PLS ranged from 19.2 to 40.3 μg L−1, from 41.6 to 72.3 μg L−1, and from 56.4 to 75.3 μg g−1 dry-soil, respectively. There was no appreciable seasonal variation in the amount of PLFAs in PW and PLS. However, the amount of PLFAs in FW tended to decrease after the middle stage of rice cultivation. Dominant PLFAs in PW and FW were 16 : 1ω7c, 18 : 1ω7, and 16 : 0 PLFAs, and those in PLS were 16 : 1ω7c, 18 : 1ω7, 16 : 0, 18 : 1ω9, i15 : 0, ai15 : 0, and 10Me17 : 0 PLFAs. The proportion of straight, mono-nnsaturated PLFAs and branched-chain PLFAs ranged from 36.6 to 64.8% and from 9.8 to 23,8% in PW, from 49.2 to 63.7% and from 12.6 to 27.5% in FW, and from 23.4 to 28.1% and 41.7 to 47.7% in PLS, respectively. Principal component analysis of the PLFA composition enabled to clearly differentiate the community structure of the microbiota in PW and FW from that in PLS. A potential indicator of the environmental stress imposed upon the microbiota expressed by the trans vs. cis ratio of 16 : 1ω7 PLFA in the PLFA composition was consistently lower in PW and FW than in PLS, suggesting that the microbial community in PW was not appreciably stressed from the percolation through PLS.