Dataset Information

Comparative Analysis of Carbon Monoxide Tolerance among Thermoanaerobacter Species.

ABSTRACT: An anaerobic thermophilic strain (strain PCO) was isolated from a syngas-converting enrichment culture. Syngas components cannot be used by strain PCO, but the new strain is very tolerant to carbon monoxide (pCO = 1.7 × 10(5) Pa, 100% CO). 16S rRNA gene analysis and DNA-DNA hybridization revealed that strain PCO is a strain of Thermoanaerobacter thermohydrosulfuricus. The physiology of strain PCO and other Thermoanaerobacter species was compared, focusing on their tolerance to carbon monoxide. T. thermohydrosulfuricus, T. brockii subsp. finnii, T. pseudethanolicus, and T. wiegelii were exposed to increased CO concentrations in the headspace, while growth, glucose consumption and product formation were monitored. Remarkably, glucose conversion rates by Thermoanaerobacter species were not affected by CO. All the tested strains fermented glucose to mainly lactate, ethanol, acetate, and hydrogen, but final product concentrations differed. In the presence of CO, ethanol production was generally less affected, but H2 production decreased with increasing CO partial pressure. This study highlights the CO resistance of Thermoanaerobacter species.

SUBMITTER: Alves JI

PROVIDER: S-EPMC5002420 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Comparative Analysis of Carbon Monoxide Tolerance among Thermoanaerobacter Species.

Alves Joana I JI Alves M Madalena MM Plugge Caroline M CM Stams Alfons J M AJ Sousa Diana Z DZ

Frontiers in microbiology 20160829

An anaerobic thermophilic strain (strain PCO) was isolated from a syngas-converting enrichment culture. Syngas components cannot be used by strain PCO, but the new strain is very tolerant to carbon monoxide (pCO = 1.7 × 10(5) Pa, 100% CO). 16S rRNA gene analysis and DNA-DNA hybridization revealed that strain PCO is a strain of Thermoanaerobacter thermohydrosulfuricus. The physiology of strain PCO and other Thermoanaerobacter species was compared, focusing on their tolerance to carbon monoxide. T ...[more]

PMID: 27621723

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Project description:Conversion of biomass-derived syngas (gaseous mixture of mainly H2, CO and CO2) to methane might be a sustainable alternative for the biofuel industry. Via the syngas route more methane can be produced from biomass than via conventional anaerobic digestion. Methanogenic archaea are key players in syngas conversion, but only a few are known to utilize CO (or syngas). Methanothermobacter thermoautotrophicus is one of the few hydrogenotrophic methanogens which has been observed to grow on CO. However, carboxydotrophic growth is slow and is reported to be readily inhibited above 50 kPa CO. The aim of this work was to get more insight of the CO metabolism in hydrogenotrophic archaea and to assess the potential toxic effects of CO towards these microorganisms. Archaeal genomic databases were searched for putative homologues of the Methanothermobacter thermoautotrophicus CODH alpha subunit (containing the catalytic site): the highest scores were for the CODH subunits of Methamothermobacter marburgensis (93% identity) and Methanococcus maripaludis (71%). M. thermoautotrophicus and the other two potential carboxydotrophic strains were incubated with CO and CO + H2 as sole substrates. In addition to M. thermoautotrophicus, M. marburgensis was able to grow methanogenically on CO alone and on CO + H2. In contrast to M. thermoautotrophicus, M. marburgensis was not as strongly inhibited when grown in presence of CO alone and was able to adapt its metabolism, shifting its lag phase from ~500 to ~100 hours. It was observed for both strains that presence of hydrogen stimulates the carbon monoxide metabolism. To gain further insight, the proteome of M. marburgensis culture grown on H2 + CO2 and H2 + CO2 + CO were analysed. Cultures grown with H2 + CO showed relative higher abundance of enzymes involved in CODH/ACS associated reactions and reactions involved in redox metabolism. Overall, the data suggests the strong reducing capacity of CO inhibits the hydrogenotrophic methanogen, making growth on CO as a sole substrate difficult for these organisms.

Project description:Carboxydothermus species are some of the most studied thermophilic carboxydotrophs. Their varied carboxydotrophic growth properties suggest distinct strategies for energy conservation via carbon monoxide (CO) metabolism. In this study, we used comparative genome analysis of the genus Carboxydothermus to show variations in the CO dehydrogenase-energy-converting hydrogenase gene cluster, which is responsible for CO metabolism with H2 production (hydrogenogenic CO metabolism). Indeed, the ability or inability to produce H2 with CO oxidation is explained by the presence or absence of this gene cluster in Carboxydothermus hydrogenoformans, Carboxydothermus islandicus, and Carboxydothermus ferrireducens Interestingly, despite its hydrogenogenic CO metabolism, Carboxydothermus pertinax lacks the Ni-CO dehydrogenase catalytic subunit (CooS-I) and its transcriptional regulator-encoding genes in this gene cluster, probably due to inversion. Transcriptional analysis in C. pertinax showed that the Ni-CO dehydrogenase gene (cooS-II) and distantly encoded energy-converting-hydrogenase-related genes were remarkably upregulated with 100% CO. In addition, when thiosulfate was available as a terminal electron acceptor in 100% CO, the maximum cell density and maximum specific growth rate of C. pertinax were 3.1-fold and 1.5-fold higher, respectively, than when thiosulfate was absent. The amount of H2 produced was only 62% of the amount of CO consumed, less than expected according to hydrogenogenic CO oxidation (CO + H2O → CO2 + H2). Accordingly, C. pertinax would couple CO oxidation by Ni-CO dehydrogenase II with simultaneous reduction of not only H2O but also thiosulfate when grown in 100% CO.IMPORTANCE Anaerobic hydrogenogenic carboxydotrophs are thought to fill a vital niche by scavenging potentially toxic CO and producing H2 as an available energy source for thermophilic microbes. This hydrogenogenic carboxydotrophy relies on a Ni-CO dehydrogenase-energy-converting hydrogenase gene cluster. This feature is thought to be common to these organisms. However, the hydrogenogenic carboxydotroph Carboxydothermus pertinax lacks the gene for the Ni-CO dehydrogenase catalytic subunit encoded in the gene cluster. Here, we performed a comparative genome analysis of the genus Carboxydothermus, a transcriptional analysis, and a cultivation study in 100% CO to prove the hydrogenogenic CO metabolism. Results revealed that C. pertinax could couple Ni-CO dehydrogenase II alternatively to the distal energy-converting hydrogenase. Furthermore, C. pertinax represents an example of the functioning of Ni-CO dehydrogenase that does not always correspond to its genomic context, owing to the versatility of CO metabolism and the low redox potential of CO.

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Dataset Information

Comparative Analysis of Carbon Monoxide Tolerance among Thermoanaerobacter Species.

Publications

Comparative Analysis of Carbon Monoxide Tolerance among Thermoanaerobacter Species.

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