Effects of Sb on AOM and microbial community in an Sb-contaminated paddy soil

Sb was amended into the paddy soil to investigate the effects of Sb contamination on AOM and the microbial communities such as methanotrophs in the paddy soil. Significant inhibition of AOM was observed in the treatment with Sb addition in comparison with the treatment without Sb addition. The similar inhibition of AOM was also determined in the treatment with the addition of the methanogenic and methanotrophic inhibitor 2-bromoethanesulfonate (BES). The significant increases in the abundance of the mcrA genes, which are responsible for methane production and oxidation, were observed in the treatment with/without Sb addition. In contrast, no significant increases in the copy number of the mcrA gene was were detected in the treatment with BES addition. These results suggested that the Sb contamination might inhibit only AOM but not methane production, while BES could inhibit both of these two pathways. In addition, amplicon high-through sequencing showed that the Sb addition impaired the diversity of microbial communities and impacted the biotic interactions in the soil. However, the abundance of bacterial methane-oxidizing phylum NC10 and its biotic connections with other microbes were enhanced by the addition of Sb. The underlying mechanisms remain unknown. On the level of genus, Pseudogulbenkiania and Methanosarcina dominated the bacterial and archaeal communities in the treatment without Sb addition, while the bacteria Ramlibacter and Geothrix and the archaea Methanomethylovorans were the most abundant genera in the treatment with Sb addition. These analyses of microbial communities indicated that Sb addition had significant effects on both the compositions of bacterial and archaeal communities and that its effects on microbial communities were different from those of BES. This study expands our knowledge of the effects of Sb contamination on AOM and the microbial (especially methanotrophs) diversity and composition in paddy soils.