Microbial community and potential arsenic-transforming microorganisms in agricultural soils

Arsenic is considered hazardous substance due to its abundance, toxicity and potential of human exposure. It can affect human health. Physical, chemical and biological approaches are available for arsenic removal. However, arsenic bioremediation has gained a great attention because it is environmental-friendly and inexpensive compared to other approaches. Microorganisms play important roles in arsenic removal through arsenic biotransformation pathways, such as arsenite oxidation, arsenate reduction and arsenic methylation. This study focused on analysis of agricultural soil microbiomes and investigation of potential arsenic-transforming microorganisms. Soil samples of the dry and wet seasons (T1 and T2) were collected from a banana plantation in Nakhonpathom, Thailand. Arsenic-contaminated soil likely results from using insecticides/pesticides. The analysis of 16S rRNA gene revealed that the most abundant phyla found in T1 and T2 were Actinobacteriota (33.78% and 15.50%), Proteobacteria (17.12% and 18.16%), Chloroflexi (13.80% and 18.15%), Firmicutes (9.04% and 12.55%), Myxococcota (6.99% and 4.82%) and Acidobacteriota (5.83% and 6.90%). Potential arsenic-transforming microorganisms are associated with arsenate reduction (Bacillus and Nocardioides), arsenic methylation (Streptomyces), and arsenic resistant (Pseudonocardia), respectively accounting for 7.02%, 3.37%, and 1.12% in T1 and 8.66%, 1.22%, and 0.22% in T2. This study suggests that soil microbiomes potentially contribute to arsenic removal.