Carboxydothermus islandicus sp. nov., a thermophilic, hydrogenogenic, carboxydotrophic bacterium isolated from a hot spring

Gelder

International Journal of Systematic and Evolutionary Microbiology

et al. 2013

Carbon monoxide is a gas present in natural and anthropogenic environments that is involved in several important redox reactions. CO metabolism is a significant part of the global carbon cycle. The number of known carboxydotrophic anaerobes is increasing in recent years due to their important role in CO conversion (Sokolova et al., 2009). CO is a potent electron donor (thermodynamic CO 2 /CO redox potential 2520 mV) and represents an excellent source of energy for anaerobic micro-organisms (Kochetkova et al., 2011; Oelgeschläger & Rother, 2008). Nevertheless, only few anaerobes have been described that exhibit the capacity for hydrogenogenic carboxydotrophy. Hydrogenogenic CO-oxidizing prokaryotes are able to grow on CO with the production of hydrogen and carbon dioxide, according to the water-gas shift reaction: CO+H 2 OAH 2 +CO 2 (DG: 220 kJ mol et al., 2001). The first organism, to our knowledge, described as being able to perform this reaction in the dark, was a mesophilic species of the genus Rhodopseudomonas (Uffen, 1976). Since then, other anaerobic CO-oxidizing hydrogenogenic prokaryotes have been described, isolated from a wide range of environments around the world and spread over different phylogenetic clades (Novikov et al., 2011;Sokolova et al., 2009;Techtmann et al., 2009). The first thermophilic carboxydotroph described, to our knowledge, was Carboxydothermus hydrogenoformans (Henstra & Stams, 2011;Svetlitchnyi et al., 2001). In this work, we describe a novel anaerobic thermophilic carboxydotrophic hydrogenogenic bacterium, strain E3-O T . Strain E3-OT was isolated from a CO-degrading enrichment culture originating from anaerobic suspended sludge from of a thermophilic municipal solid waste digester in Barcelona, Spain.A phosphate-buffered mineral salt medium (20 mM, pH 7.0) was used for enrichment cultures and isolation of strain E3-O T .The phosphate-buffered mineral medium contained the following components (l 21 ): Na 2 HPO 4 , 1.63 g; NaH 2 PO 4 , 1.02 g; resazurin, 0.5 g; NH 4 Cl, 0.3 g; CaCl 2 . 2H 2 O, 0.11 g; MgCl 2 . 6H 2 O, 0.10 g; NaCl, 0.3 g; 1 ml each of acid and alkaline trace element stock and 0.2 ml vitamin stock. Medium was reduced with 0.8 mM sodium sulfide before inoculation. Trace elements and Abbreviations: AQDS, anthraquinone-2,6-disulfonate; DGGE, denaturing gradient gel electrophoresis.The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of Moorella stamsii strain E3-O T is HF563589.

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confidence: 99%

Moorella stamsii sp. nov., a new anaerobic thermophilic hydrogenogenic carboxydotroph isolated from digester sludge

Gelder

International Journal of Systematic and Evolutionary Microbiology

et al. 2013

International Journal of Systematic and Evolutionary Microbiology

“…*Values of CFAs of C. islandicus grown on CO (Novikov et al, 2011). DData are from this study apart from data in parentheses, which are taken from previous reports.…”

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confidence: 99%

“…Data for reference strains are taken from Novikov et al (2011). Only fatty acids present at .5 % in any one of the strains are shown.…”

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confidence: 99%

Carboxydothermus pertinax sp. nov., a thermophilic, hydrogenogenic, Fe(III)-reducing, sulfur-reducing carboxydotrophic bacterium from an acidic hot spring

Yoneda

Yoshida

Kawaichi

et al. 2012

A novel anaerobic, Fe(III)-reducing, hydrogenogenic, carboxydotrophic bacterium, designated strain Ug1 T , was isolated from a volcanic acidic hot spring in southern Kyushu Island, Japan. Cells of the isolate were rod-shaped (1.0-3.0 mm long) and motile due to peritrichous flagella. Strain Ug1 T grew chemolithoautotrophically on CO (100 % in the gas phase) with reduction of ferric citrate, amorphous iron (III) oxide, 9,10-anthraquinone 2,6-disulfonate, thiosulfate or elemental sulfur. No carboxydotrophic growth occurred with sulfate, sulfite, nitrate or fumarate as electron acceptor. During growth on CO, H 2 and CO 2 were produced. Growth occurred on molecular hydrogen as an energy source and carbon dioxide as a sole carbon source. Growth was observed on various organic compounds under an N 2 atmosphere with the reduction of ferric iron. The temperature range for carboxydotrophic growth was 50-70 6C, with an optimum at 65 6C. The pH 25 6C range for growth was 4.6-8.6, with an optimum between 6.0 and 6.5. The doubling time under optimum conditions using CO with ferric citrate was 1.5 h. The DNA G+C content was 42.2 mol%. Analysis of 16S rRNA gene sequences demonstrated that this strain belongs to the thermophilic carboxydotrophic bacterial genus Carboxydothermus, with sequence similarities of 94.1-96.6 % to members of this genus. The isolate can be distinguished from other members of the genus Carboxydothermus by its ability to grow with elemental sulfur or thiosulfate coupled to CO oxidation. On the basis of phylogenetic analysis and unique physiological features, the isolate represents a novel species of the genus Carboxydothermus for which the name Carboxydothermus pertinax sp. nov. is proposed; the type strain of the novel species is Ug1 T (5DSM 23698 T 5NBRC 107576 T ).

“…Carboxydothermus species have been reported as facultative carboxydotrophs (15)(16)(17)(18)(19). They can grow heterotrophically on lactate or pyruvate with available electron acceptors.…”

Section: Resultsmentioning

confidence: 99%

“…The genus Carboxydothermus has been one of the most studied models of thermophilic carboxydotrophy. To date, five Carboxydothermus species have been described (15)(16)(17)(18)(19); all of them are strictly anaerobic, thermophilic, and neutrophilic and have been isolated as facultative carboxydotrophs from terrestrial hot springs (15)(16)(17)(18)(19). The genus is characterized by varied energy conservation strategies via CO oxidation.…”

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confidence: 99%

Insight into Energy Conservation via Alternative Carbon Monoxide Metabolism in Carboxydothermus pertinax Revealed by Comparative Genome Analysis

Fukuyama

Omae

Yoneda

et al. 2018

Appl Environ Microbiol

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 to show variations in the CO dehydrogenase-energy-converting hydrogenase gene cluster, which is responsible for CO metabolism with H production (hydrogenogenic CO metabolism). Indeed, the ability or inability to produce H with CO oxidation is explained by the presence or absence of this gene cluster in ,, and Interestingly, despite its hydrogenogenic CO metabolism, 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 showed that the Ni-CO dehydrogenase gene () 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 were 3.1-fold and 1.5-fold higher, respectively, than when thiosulfate was absent. The amount of H produced was only 62% of the amount of CO consumed, less than expected according to hydrogenogenic CO oxidation (CO + HO → CO + H). Accordingly, would couple CO oxidation by Ni-CO dehydrogenase II with simultaneous reduction of not only HO but also thiosulfate when grown in 100% CO. Anaerobic hydrogenogenic carboxydotrophs are thought to fill a vital niche by scavenging potentially toxic CO and producing H 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 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, a transcriptional analysis, and a cultivation study in 100% CO to prove the hydrogenogenic CO metabolism. Results revealed that could couple Ni-CO dehydrogenase II alternatively to the distal energy-converting hydrogenase. Furthermore, 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.