Abstract
Carbon monoxide (CO) is an important intermediate in anaerobic carbon fixation pathways in acetogenesis and methanogenesis. In addition, some anaerobes can utilize CO as an energy source. In the hyperthermophilic archaeon Thermococcus onnurineus, which grows optimally at 80°C, CO oxidation and energy conservation is accomplished by a respiratory complex encoded by a 16-gene cluster containing a CO dehydrogenase, a membrane-bound [NiFe]-hydrogenase and a Na+/H+ antiporter module. This complex oxidizes CO, evolves CO2 and H2, and generates a Na+ motive force that is used to conserve energy by a Na+-dependent ATP synthase. Herein we used a bacterial artificial chromosome to insert the 13.2 kb gene cluster encoding the CO-oxidizing respiratory complex of T. onnurineus into the genome of the heterotrophic archaeon, Pyrococcus furiosus, which grows optimally at 100°C. P. furiosus is normally unable to utilize CO, however, the recombinant strain readily oxidized CO and generated H2 at 80°C. Moreover, CO also served as an energy source and allowed the P. furiosus strain to grow with a limiting concentration of sugar or with peptides as the carbon source. Moreover, CO oxidation by P. furiosus was also coupled to the re-utilization, presumably for biosynthesis, of acetate generated by fermentation. The functional transfer of CO utilization between Thermococcus and Pyrococcus species demonstrated herein is representative of the horizontal gene transfer of an environmentally relevant metabolic capability. The transfer of CO utilizing, hydrogen-producing genetic modules also has applications for biohydrogen production and a CO-based industrial platform for various thermophilic organisms.
Highlights
IntroductionAnaerobic microorganisms that directly use Carbon monoxide (CO) as a carbon source do so via the Wood-Ljungdahl pathway
Carbon monoxide (CO) is a high energy compound with a very low reduction potential for the CO/CO2 couple [E0 = -524 mV: (Thauer, 1990)], see Equation 1.CO + H2O → CO2 + 2H+ + 2e− (1)Engineering a Hyperthermophile to Use COAnaerobic microorganisms that directly use CO as a carbon source do so via the Wood-Ljungdahl pathway
We show that the 16-gene cluster encoding the trimodular respiratory Codh complex (Mrp-MbhCodh) can be functionally transferred between Thermococcales species
Summary
Anaerobic microorganisms that directly use CO as a carbon source do so via the Wood-Ljungdahl pathway. This is present in acetogenic bacteria and methanogenic archaea (Wood, 1991; Costa and Leigh, 2014) and has been studied for more than 80 years (Drake and Daniel, 2004). The key enzyme is a bifunctional and bimodular CO dehydrogenase/acetyl-CoA synthase (Codh/Acs) complex. This enzyme combines CO with a methyl group, donated by a corrinoid containing carrier protein, with coenzyme A to generate acetyl-CoA (Ragsdale et al, 1996). One reduces CO2 to the level of the methyl group in acetyl-CoA while the other reduces CO2 to CO, which forms the carbonyl group of acetyl-CoA (Schuchmann and Muller, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
