Effects of different antimony contamination levels on paddy soil bacterial diversity and community structure

To clarify the response mechanism of paddy soil microorganisms to contamination caused by antimony (Sb) alone, we added K(SbO)C₄H₄O₆.1/2 H₂O with different contents to uncontaminated paddy soil and carried out related studies. 16S rRNA was sequenced in V3-V4 regions of paddy soil bacteria with different Sb contamination levels. Then, α diversity and species enrichment and separation of paddy soil microorganisms were analyzed. The biochemical behavior and the influences of Sb fractions on bacterial communities and ecological function were explored in paddy soil with different contamination levels. The results showed that the contents of Sb_tot and Sb(V) increased with the increase of contamination level, and the difference was significant among the groups. For Sb_exe and Sb_srp there were slight differences between S100 and S200 groups, but significant differences among other groups. The diversity index increased with the increase of Sb concentration, which reached the maximum value in S200 group and the minimum value in control group (SC). The relative importance analysis demonstrated that Sb(III) and Sb_srp were the main Sb fractions affecting the diversity index of bacterial community. In addition, the results of principal coordinate analysis (PCoA) showed that there were significant differences between the bacterial communities in SC and in the soil with different Sb contamination levels. Based on diversity analysis, it was found that Proteobacteria, Actinobacteria and Bacteroidetes were the main dominant phyla in paddy soil with different Sb concentrations, and their enrichment and separation were greater than those of other dominant phyla. Though the Static Bayesian network inference, it was shown that Sb_tot affected Sphingomonadaceae, and Sb_srp affected Burkholderiaceae, Xanthomonadaceae and Acidobacteriale to further affect bacterial communities, while Sb(V) mainly affected Flavobacteriaceae, Rhodopirillaceae and Acidobacteriale. The above results provide a scientific basis for the biochemical restoration potential of paddy soils with different Sb contamination levels.