Succession of microbiota estimated by phospholipid fatty acid analysis and changes in organic constituents during the composting process of rice straw

The succession of responsible microbiota, during the composting process of rice straw (RS) was studied for 145 d in relation to the changes in the organic constituents of RS. During the composting process, the C/N ratio of RS decreased from 56 to 22. On a C basis, the relative contents of lipid, water-soluble organic matter (WSOM), hemicellulose, cellulose, and lignin fractions in RS changed from 5.6, 8.9, 32.9, 17.9, and 34.0%, to 7.3, 5.8, 30.7, 3.8, and 51.1%, respectively, indicating that the cellulose fraction was mainly decomposed in the composting process. Biomass C accounted for 18.3% (on day 75 when the total amount of phospholipid fatty acids (PLFAs) reached a peak) and 11.5% (at the end of composting) of the total C of RS under the composting process. As for PLFAs, the biomarkers of fungi and Gram-negative bacteria predominated in the RS material used. At the thermophilic stage (the first 2 weeks), biomarkers of Gram-positive bacteria and actinomycetes predominated. After the thermophilic stage, biomarkers of other Gram-positive bacteria became dominant. Finally, at the curing stage, the proportion of the biomarkers of Gram-negative bacteria and eukaryotes increased, indicating the co-contribution of Gram-positive and Gram-negative bacteria and fungi in the decomposition process at this stage. The trans/cis ratio of 16 : 1omega7 PLFA of RS under the composting process ranged from 0.18 to 0.30, indicating that the composting process of RS prepared a significantly lower environmental stress (P < 0.01) compared to the decomposition of RS in a submerged paddy soil.