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Müller, H.* ; Marozava, S. ; Probst, A.J.* ; Meckenstock, R.U.*

Groundwater cable bacteria conserve energy by sulfur disproportionation.

ISME J. 14, 623-634 (2020)
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Cable bacteria of the family Desulfobulbaceae couple spatially separated sulfur oxidation and oxygen or nitrate reduction by long-distance electron transfer, which can constitute the dominant sulfur oxidation process in shallow sediments. However, it remains unknown how cells in the anoxic part of the centimeter-long filaments conserve energy. We found 16S rRNA gene sequences similar to groundwater cable bacteria in a 1-methylnaphthalene-degrading culture (1MN). Cultivation with elemental sulfur and thiosulfate with ferrihydrite or nitrate as electron acceptors resulted in a first cable bacteria enrichment culture dominated >90% by 16S rRNA sequences belonging to the Desulfobulbaceae. Desulfobulbaceae-specific fluorescence in situ hybridization (FISH) unveiled single cells and filaments of up to several hundred micrometers length to belong to the same species. The Desulfobulbaceae filaments also showed the distinctive cable bacteria morphology with their continuous ridge pattern as revealed by atomic force microscopy. The cable bacteria grew with nitrate as electron acceptor and elemental sulfur and thiosulfate as electron donor, but also by sulfur disproportionation when Fe(Cl)(2) or Fe(OH)(3) were present as sulfide scavengers. Metabolic reconstruction based on the first nearly complete genome of groundwater cable bacteria revealed the potential for sulfur disproportionation and a chemo-litho-autotrophic metabolism. The presence of different types of hydrogenases in the genome suggests that they can utilize hydrogen as alternative electron donor. Our results imply that cable bacteria not only use sulfide oxidation coupled to oxygen or nitrate reduction by LDET for energy conservation, but sulfur disproportionation might constitute the energy metabolism for cells in large parts of the cable bacterial filaments.
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Publication type Article: Journal article
Document type Scientific Article
Keywords Targeted Oligonucleotide Probes; In-situ Hybridization; Sequence Similarity; Sulfide Oxidation; Iron; Reduction; Transport; Alignment; Resource; Nitrate
ISSN (print) / ISBN 1751-7362
e-ISSN 1751-7370
Journal ISME Journal
Quellenangaben Volume: 14, Issue: 2, Pages: 623-634 Article Number: , Supplement: ,
Publisher Nature Publishing Group
Publishing Place Macmillan Building, 4 Crinan St, London N1 9xw, England
Reviewing status Peer reviewed