Comparison of community structures of microbiota at main habitats in rice field ecosystems based on phospholipid fatty acid analysis

Abstract

The present study compares the community structures of microbiota at different habitats in Japanese rice fields by comparing their phospholipid fatty acid (PLFA) compositions to understand the contribution of different habitats to microbiological diversity. The data were collected from four neighboring rice fields. Comparison was made for the PLFA compositions extracted from the floodwater, percolating water, rice soils under flooded and drained conditions, rice straw (RS) placed in flooded and drained rice soils, RS in the composting process, and RS compost placed in a flooded rice field. Average amounts of PLFAs were 33 μg L−1 in the floodwater, 17.1 μg L−1 in the percolating water from plow layers, 34.6 μg L−1 in the percolating water from subsoil layers, 108 μg g−1 dry weight basis (dw) in flooded rice soils, 382 μg g−1 dw in RS materials, 2,510 μg g−1 dw in RS composts, 2,850 μg g−1 dw in RS composts after application to a flooded rice soil, 222 μg g−1 wet weight basis (ww) in RS in drained rice soils, and 284 μg g−1 ww in RS in flooded rice soils. The total amount of PLFAs to the soil depth of 10 cm was estimated to be about 12 g m−2. The PLFA compositions were different from each other depending on the habitats. Rice soils were characterized by the predominance of actinomycetes and Gram-positive bacteria in comparison with the other habitats. In contrast, the microbial communities in the floodwater and percolating water were characterized by the predominance of Gram-negative bacteria and eukaryotes (presumably algae), and Gram-negative bacteria, respectively. The microbial community of RS materials was dominated by fungi. Gram-positive bacteria became predominant in RS after application to flooded rice soils, while RS placed in a drained rice field after harvesting rice was characterized by the predominance of Gram-negative bacteria and fungi. The community structures at respective habitats were stable and specific, irrespective of the season of sampling and the duration of decomposition of RS.