Biogeochemical characterization of bacterial assemblages in relation to release of arsenic from South East Asia (Bangladesh) sediments

Arsenic release experiments using natural indigenous microbial assemblages and natural sediment samples in Bangladesh have been performed. The As release appears to be facilitated by moderate organic input. Addition of some nutrients caused reducing conditions, which may generate the appropriate environment for Fe-reducing bacteria to become active. Detailed cellular phospholipid fatty acid (PLFA) analysis suggests the presence of SO4-reducing and Fe-reducing bacteria in the sediments. These Fe-reducing bacteria may serve as the agents catalyzing As release in the organic-rich sediments. 16S rDNA analysis of one cultured sample suggests the presence of clostridia, some of which are known to mediate Fe reduction. Based on new PLFA analyses, it is proposed that combined microbial processes of SO4 reduction to generate anaerobic conditions and Fe reduction to co-reduce As are important biogeochemical factors for As release in the Bangladesh sediments.