sp. nov., an acidophilic, metal-resistant sulfate-reducing bacterium from acid mine drainage.

A novel, spore-forming, acidophilic and metal-resistant sulfate-reducing bacterium, strain OL, was isolated from a microbial mat in a tailing dam at a gold ore mining site. Cells were slightly curved immotile rods, 0.5 µm in diameter and 2.0-3.0 µm long. Cells were stained Gram-negative, despite the Gram-positive cell structure revealed by electron microscopy of ultrathin layers. OL grew at pH 4.0-7.0 with an optimum at 5.5. OL utilised H, lactate, pyruvate, malate, formate, propionate, ethanol, glycerol, glucose, fructose, sucrose, peptone and tryptone as electron donors for sulfate reduction. Sulfate, sulfite, thiosulfate, nitrate and fumarate were used as electron acceptors in the presence of lactate. Elemental sulfur, iron (III), and arsenate did not serve as electron acceptors. The major cellular fatty acids were Cω7 (39.0 %) and C (12.1 %). The draft genome of OL was 5.29 Mb in size and contained 4909 protein-coding genes. The 16S rRNA gene sequence placed OL within the phylum , class , family , genus 59.4B was the closest relative with 97.6 % sequence similarity. On the basis of phenotypic and phylogenetic characteristics, strain OL represents a novel species within the genus , for which we propose the name sp. nov. with the type strain OL (=DSM 104464=VKM В-3021).