@article {3045, title = {H Is a Major Intermediate in Corrosion of Iron.}, journal = {mBio}, volume = {14}, year = {2023}, month = {2023 Apr 25}, pages = {e0007623}, abstract = {

Desulfovibrio vulgaris has been a primary pure culture sulfate reducer for developing microbial corrosion concepts. Multiple mechanisms for how it accepts electrons from Fe have been proposed. We investigated Fe oxidation with a mutant of in which hydrogenase genes were deleted. The hydrogenase mutant grew as well as the parental strain with lactate as the electron donor, but unlike the parental strain, it was not able to grow on H. The parental strain reduced sulfate with Fe as the sole electron donor, but the hydrogenase mutant did not. H accumulated over time in Fe cultures of the hydrogenase mutant and sterile controls but not in parental strain cultures. Sulfide stimulated H production in uninoculated controls apparently by both reacting with Fe to generate H and facilitating electron transfer from Fe to H. Parental strain supernatants did not accelerate H production from Fe, ruling out a role for extracellular hydrogenases. Previously proposed electron transfer between Fe and via soluble electron shuttles was not evident. The hydrogenase mutant did not reduce sulfate in the presence of Fe and either riboflavin or anthraquinone-2,6-disulfonate, and these potential electron shuttles did not stimulate parental strain sulfate reduction with Fe as the electron donor. The results demonstrate that primarily accepts electrons from Fe via H as an intermediary electron carrier. These findings clarify the interpretation of previous corrosion studies and suggest that H-mediated electron transfer is an important mechanism for iron corrosion under sulfate-reducing conditions. Microbial corrosion of iron in the presence of sulfate-reducing microorganisms is economically significant. There is substantial debate over how microbes accelerate iron corrosion. Tools for genetic manipulation have only been developed for a few Fe(III)-reducing and methanogenic microorganisms known to corrode iron and in each case those microbes were found to accept electrons from Fe via direct electron transfer. However, iron corrosion is often most intense in the presence of sulfate-reducing microbes. The finding that Desulfovibrio vulgaris relies on H to shuttle electrons between Fe and cells revives the concept, developed in some of the earliest studies on microbial corrosion, that sulfate reducers consumption of H is a major microbial corrosion mechanism. The results further emphasize that direct Fe-to-microbe electron transfer has yet to be rigorously demonstrated in sulfate-reducing microbes.

}, keywords = {Corrosion, Desulfovibrio, Desulfovibrio vulgaris, Hydrogenase, Iron, Lactic Acid, Oxidation-Reduction, Sulfates}, issn = {2150-7511}, doi = {10.1128/mbio.00076-23}, author = {Woodard, Trevor L and Ueki, Toshiyuki and Lovley, Derek R} } @article {3082, title = {The Hydrogen Economy of Methanosarcina barkeri: Life in the Fast Lane.}, journal = {J Bacteriol}, volume = {200}, year = {2018}, month = {2018 Oct 15}, abstract = {

Two recent studies (T. D. Mand, G. Kulkarni, and W. W. Metcalf, J. Bacteriol 200:e00342-18, 2018, https://doi.org/10.1128/JB.00342-18, and G. Kulkarni, T. D. Mand, and W. W. Metcalf, mBio 9:e01256-18, 2018, https://doi.org/10.1128/mBio.01256-18) analyzed an impressive array of hydrogenase-deficient mutant strains of not only to describe H-based growth but also to demonstrate the conservation of energy with intracellular hydrogen cycling, a novel strategy for creating a proton motive force to support ATP synthesis.

}, keywords = {Hydrogen, Hydrogenase, Methane, Methanosarcina barkeri, Proton-Motive Force}, issn = {1098-5530}, doi = {10.1128/JB.00445-18}, author = {Lovley, Derek R} } @article {411, title = {Role of the NiFe hydrogenase Hya in oxidative stress defense in Geobacter sulfurreducens.}, journal = {J Bacteriol}, volume = {194}, year = {2012}, month = {2012 May}, pages = {2248-53}, abstract = {Geobacter sulfurreducens, an Fe(III)-reducing deltaproteobacterium found in anoxic subsurface environments, contains 4 NiFe hydrogenases. Hyb, a periplasmically oriented membrane-bound NiFe hydrogenase, is essential for hydrogen-dependent growth. The functions of the three other hydrogenases are unknown. We show here that the other periplasmically oriented membrane-bound NiFe hydrogenase, Hya, is necessary for growth after exposure to oxidative stress when hydrogen or a highly limiting concentration of acetate is the electron source. The beneficial impact of Hya on growth was dependent on the presence of H(2) in the atmosphere. Moreover, the Hya-deficient strain was more sensitive to the presence of superoxide or hydrogen peroxide. Hya was also required to safeguard Hyb hydrogen oxidation activity after exposure to O(2). Overexpression studies demonstrated that Hya was more resistant to oxidative stress than Hyb. Overexpression of Hya also resulted in the creation of a recombinant strain better fitted for exposure to oxidative stress than wild-type G. sulfurreducens. These results demonstrate that one of the physiological roles of the O(2)-resistant Hya is to participate in the oxidative stress defense of G. sulfurreducens.}, keywords = {Bacterial Proteins, Gene Expression Regulation, Bacterial, Geobacter, Hydrogen Peroxide, Hydrogenase, Mutation, Oxidative Stress, Oxygen, Reactive Oxygen Species, Reverse Transcriptase Polymerase Chain Reaction, Xanthine Oxidase}, issn = {1098-5530}, doi = {10.1128/JB.00044-12}, author = {Tremblay, Pier-Luc and Lovley, Derek R} } @article {1219, title = {Key role for sulfur in peptide metabolism and in regulation of three hydrogenases in the hyperthermophilic archaeon Pyrococcus furiosus.}, journal = {J Bacteriol}, volume = {183}, year = {2001}, month = {2001 Jan}, pages = {716-24}, abstract = {

The hyperthermophilic archaeon Pyrococcus furiosus grows optimally at 100 degrees C by the fermentation of peptides and carbohydrates. Growth of the organism was examined in media containing either maltose, peptides (hydrolyzed casein), or both as the carbon source(s), each with and without elemental sulfur (S(0)). Growth rates were highest on media containing peptides and S(0), with or without maltose. Growth did not occur on the peptide medium without S(0). S(0) had no effect on growth rates in the maltose medium in the absence of peptides. Phenylacetate production rates (from phenylalanine fermentation) from cells grown in the peptide medium containing S(0) with or without maltose were the same, suggesting that S(0) is required for peptide utilization. The activities of 14 of 21 enzymes involved in or related to the fermentation pathways of P. furiosus were shown to be regulated under the five different growth conditions studied. The presence of S(0) in the growth media resulted in decreases in specific activities of two cytoplasmic hydrogenases (I and II) and of a membrane-bound hydrogenase, each by an order of magnitude. The primary S(0)-reducing enzyme in this organism and the mechanism of the S(0) dependence of peptide metabolism are not known. This study provides the first evidence for a highly regulated fermentation-based metabolism in P. furiosus and a significant regulatory role for elemental sulfur or its metabolites.

}, keywords = {Culture Media, Cytoplasm, Gene Expression Regulation, Archaeal, Gene Expression Regulation, Enzymologic, Glycolysis, Hydrogenase, Membrane Proteins, Oxidation-Reduction, Peptides, Pyrococcus furiosus, Sulfur}, issn = {0021-9193}, doi = {10.1128/JB.183.2.716-724.2001}, author = {Adams, M W and Holden, J F and Menon, A L and Schut, G J and Grunden, A M and Hou, C and Hutchins, A M and Jenney, F E and Kim, C and Ma, K and Pan, G and Roy, R and Sapra, R and Story, S V and Verhagen, M F} }