Dominance of Oscillospira and Bacteroides in the bacterial community associated with the degradation of high-concentration dimethyl sulfide under iron-reducing condition

Microbial consumption of high-concentration dimethyl sulfide (DMS) under various redox conditions was investigated with freshwater sediments as inoculum. After about 1-year cyclic static enrichment at an initial DMS concentration of 10 mM, it was found that addition of ferric iron can lead to better DMS degradation efficiency compared to bicarbonate, nitrate, and oxygen as the electron acceptors especially, significantly higher than sulfate addition. The rate constant of DMS degradation was only 0.01106 +/- 0.00139 day(-1) under sulfate reduction, but increased to 0.02355 +/- 0.00173 day(-1) under iron reduction. Enriched bacterial communities under both aerobic and iron-reducing conditions were highly organized. Thus, the specialized bacterial communities were responsible for the different degradation conditions. The genera Thiobacillus and Pseudomona, which had been found previously to be capable of DMS degradation, belong to the most abundant bacteria in the aerobic microbial community. In the iron-reducing community, the four genera Oscillospira, Bacteroides, Parabacteroides, and Petrimonas are dominant, and in total account for 88 % of the total bacterial sequences. Species from the four anaerobic genera might be involved in ferric reduction and/or high-concentration DMS degradation. Thus, sediments in eutrophic lakes might harbor a diverse of functionally specific bacteria for DMS degradation.