Enhancement effects of decabromodiphenyl ether on microbial sulfate reduction in eutrophic lake sediments: A study on...

Although sulfate (SO₄^2-) reduction by sulfate-reducing bacteria (SRB) is an important sulfur cycling processes, little is known about how the persistent organic pollutants affect the SO₄^2- reduction process in the eutrophic lake sediments. Here, we carried out a 120-day microcosm experiment to explore the effects of decabromodiphenyl ether (BDE-209) on SO₄^2- reduction mediated by SRB in sediment collected from Taihu Lake, a typical eutrophic lake in China. The results showed that BDE-209 contamination significantly enhanced the activity of dissimilatory sulfite reductase (DSR) (r = 0.83), which led to an increased concentration of sulfide produced by SO₄^2- reduction. This stimulatory effect of BDE-209 on DSR activity was closely related to variations in the dsrA- and dsrB-type SRB communities. The abundances and diversities of the dsrA- and dsrB-containing SRB increased and their community composition varied in response to BDE-209 contamination. The gene copies (r = 0.72), Chao 1 (r = 0.50), Shannon (r = 0.55), and Simpson (r = 0.70) indices of dsrB-containing SRB was positively correlated with BDE-209 contamination. Co-occurrence network analysis revealed that network complexity, connectivity, and the interspecific cooperative relationship in SRB were strengthened by BDE-209 contamination. The keystone species identified in the SRB community mainly belonged to the genera Candidatus Sulfopaludibacter for the dsrA-containing SRB and Desulfatiglans for the dsrB-containing SRB, and their relative abundances were positively correlated with DSR activity in the sediment. The relative abundance of the keystone species and SRB diversity were important microbial factors directly contributing to the variations in DSR activity based on structural equation modeling analysis. Notably, the results of abundance, community structure, and interspecific relationships showed that the dsrB-containing SRB may be more sensitive to the BDE-209 contamination than the dsrA-containing SRB. These results will help us understand the effects of BDE-209 on microbial sulfate reduction in eutrophic lakes.