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

Abstract

A novel, spore-forming, acidophilic and metal-resistant sulfate-reducing bacterium, strain OLT, 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. OLT grew at pH 4.0–7.0 with an optimum at 5.5. OLT utilised H2, 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 C16:1ω7c (39.0 %) and C16 : 0 (12.1 %). The draft genome of OLT was 5.29 Mb in size and contained 4909 protein-coding genes. The 16S rRNA gene sequence placed OLT within the phylum Firmicutes , class Clostridia , family Peptococcaceae , genus Desulfosporosinus. Desulfosporosinus nitroreducens 59.4BT was the closest relative with 97.6 % sequence similarity. On the basis of phenotypic and phylogenetic characteristics, strain OLT represents a novel species within the genus Desulfosporosinus , for which we propose the name Desulfosporosinus metallidurans sp. nov. with the type strain OLT (=DSM 104464T=VKM В−3021T).

Acetate Degradation at Low pH by the Moderately Acidophilic Sulfate Reducer Acididesulfobacillus acetoxydans gen. nov. sp. nov.

“… Desulfosporosinus acididurans ( Sánchez-Andrea et al, 2015 ), Desulfosporosinus acidiphilus ( Alazard et al, 2010 ), Desulfosporosinus metallidurans ( Panova et al, 2021 ), Desulfosporosinus orientis ( Adams and Postgate, 1959 ; Campbell and Postgate, 1965 ; Klemps et al, 1985 ; Robertson et al, 2001 ; Ramamoorthy et al, 2006 ), Desulfitobacterium dehalogenans ( Utkin et al, 1994 ), Desulfitobacterium metallireducens ( Finneran et al, 2002 ). +, supported growth; −, did not support growth; (+), weak growth.…”

“…acididurans (pH 3.8–7.0, optimum 5.5; Sánchez-Andrea et al, 2015 ), and Ds. metallidurans (pH 4.0–7.0, optimum 5.5; Panova et al, 2021 ).…”

“…The capacity for complete oxidation of organic acids to CO 2 is not common in other acidophilic/acidotolerant SRB described so far ( Alazard et al, 2010 ; Sánchez-Andrea et al, 2013 , 2015 ) and was only recently reported to promote limited growth in Ds. metallidurans ( Panova et al, 2021 ). Because of the increasing toxicity of organic acids at pH values below their pK a , lowering their concentration by complete oxidation likely constituted an important detoxification mechanism for A. acetoxydans strain INE.…”

“…metallidurans , where weak growth on acetic acid was reported. However, acetate oxidation was proposed to occur through the TCA cycle instead of the Acetyl-CoA pathway based on genome analysis ( Panova et al, 2021 ).…”

“…The in-depth study of the physiology and dominant stress resistance mechanisms of acidophilic SRB requires pure culture isolates. So far, only a few moderately acidophilic or acidotolerant SRB species have been described, Thermodesulfobium narugense (pH 4.0–6.5; Mori et al, 2003 ) and T. acidiphilum (pH 3.7–6.5; Frolov et al, 2017 ), both from the genus Thermodesulfobium within the family Thermodesulfobiaceae ; Desulfothermobacter acidiphilus (pH 2.9–6.5; Frolov et al, 2018 ) from the family Thermoanaerobacteraceae ; and Desulfosporosinus acididurans (pH 3.8-7.0; Sánchez-Andrea et al, 2015 ), D. acidiphilus (pH 3.6–5.5; Alazard et al, 2010 ), and D. metallidurans (pH 4.0–7.0; Panova et al, 2021 ) from the genus Desulfosporosinus in the family Peptococcaceae of the Clostridia class in the Firmicutes phylum. Here, we report the characterization of a novel moderately acidophilic SRB from a novel genus, Acididesulfobacillus acetoxydans strain INE, enriched from Tinto River sediments ( Sánchez-Andrea et al, 2013 ).…”