Abstract
Thermoanaerobacter kivui is a thermophilic acetogen that can grow on carbon monoxide as sole carbon and energy source. To identify the gene(s) involved in CO oxidation, the genome sequence was analyzed. Two genes potentially encoding CO dehydrogenases were identified. One, cooS, potentially encodes a monofunctional CO dehydrogenase, whereas another, acsA, potentially encodes the CODH component of the CODH/ACS complex. Both genes were cloned, a His-tag encoding sequence was added, and the proteins were produced from a plasmid in T. kivui. His-AcsA copurified by affinity chromatography with AcsB, the acetyl-CoA synthase of the CO dehydrogenase/acetyl CoA synthase complex. His-CooS copurified with CooF1, a small iron-sulfur center containing protein likely involved in electron transport. Both protein complexes had CO:ferredoxin oxidoreductase as well as CO:methyl viologen oxidoreductase activity, but the activity of CooSF1 was 15-times and 231-times lower, respectively. To underline the importance of CooS, the gene was deleted in the CO-adapted strain. Interestingly, the ∆cooS deletion mutant did not grow on CO anymore. These experiments clearly demonstrated that CooS is essential for growth of T. kivui on CO. This is in line with the hypothesis that CooS is the CO-oxidizing enzyme in cells growing on CO.
Highlights
Carbon monoxide is an abundant atmospheric trace gas originating from biotic and abiotic sources (Stegenta-Dabrowska et al 2019)
T. kivui is a thermophilic acetogen with a high potential as catalyst in carbon capture and storage as well as utilization (Müller 2019)
The molecular basis for this adaptation still remains elusive but here we have identified the CO dehydrogenase gene that is essential for growth on CO
Summary
Carbon monoxide is an abundant atmospheric trace gas originating from biotic and abiotic sources (Stegenta-Dabrowska et al 2019). Despite its high toxicity to many life forms, specialized bacteria and archaea are known to use carbon monoxide as electron and carbon source for growth (Henstra et al 2007a; Sokolova et al 2009; Robb and Techtmann 2018). These carboxydotrophs can be either aerobic or anaerobic but they share a common key enzyme, the CO dehydrogenase (CODH) (Ragsdale 2000; Dobbek et al 2001).
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