A novel community of acidophiles in an acid mine drainage sediment

A sediment sample (pH 2.5) was collected at an acid mine drainage site in Anhui, China. The present acidophilic microbial community in the sediment was studied with a 16S rRNA gene clone library. Small-subunit rRNA genes were PCR amplified, cloned and screened by amplified rDNA restriction analysis (ARDRA). Subsequently, 10 different clones were identified and they were affiliated with Acidobacteria, beta/gamma-Proteobacteria, delta-Proteobacteria, Nitrospira, Candidate division TM7, and Low G + C Gram-positives. Phylogenetic analysis of 16S rRNA gene sequences revealed a diversity of acidophiles in the sediment that were mostly novel. Unexpectedly, 16S rRNA gene sequences affiliated with delta-Proteobacteria were found to constitute more than 60% of clone library. To our knowledge, this is the first occasion that bacteria of delta-Proteobacteria have been found dominant in the acidic habitat. Anaerobic sulfate- or metal reduction is the predominant physiological trait of bacteria of this subdivision. The high sulfate, ferric iron and the presence of bioavailable carbon in the anaerobic microenvironment may result in the dominance of bacteria of delta-Proteobacteria.