A Novel CO-Dependent Transcriptional Regulator and Enhanced H2 Production by an Engineered Thermococcus onnurineus NA1

Abstract

Genomic analysis suggested the existence of a CO-dependent transcriptional regulator composed of the CorQ with a V4R domain and the CorR with a DNA-binding domain of LTTR family in a carboxydotrophic hydrogenogenic Thermococcus onnurineus NA1. CorQR homologs were identified in three other Thermococcus strains and a Candidatus Korarchaeum cryptofilum OPF8. Using the mutant strains with deletion of corQ or corR, it was demonstrated that CorQR serve as a positive transcriptional regulator for expression of a gene cluster composed of a carbon monoxide dehydrogenase (CODH), a hydrogenase and a Na+/H+ antiporter. The mutant strain, MC02, with overexpression of corQR showed 2 to 7-fold higher transcripts and 2 to 4-fold higher proteins from the CODH gene cluster than the wild-type strain. The overexpression of the transcriptional regulator resulted in a 4-fold increase in H2 production in a bioreactor culture compared to the wild-type strain. To the best of our knowledge, the engineered strain exhibited the highest H2 production rate of 171 mmol liter-1 h-1 and specific H2 production rate of 237 mmol g-1 h-1 among CO-dependent H2-producing microbes studied to date.A1. CorQR homologs were identified in three other Thermococcus strains and a Candidatus Korarchaeum cryptofilum OPF8. Using the mutant strains with deletion of corQ or corR, it was demonstrated that CorQR serve as a positive transcriptional regulator for expression of a gene cluster composed of a carbon monoxide dehydrogenase (CODH), a hydrogenase and a Na+/H+ antiporter. The mutant strain, MC02, with overexpression of corQR showed 2 to 7-fold higher transcripts and 2 to 4-fold higher proteins from the CODH gene cluster than the wild-type strain. The overexpression of the transcriptional regulator resulted in a 4-fold increase in H2 production in a bioreactor culture compared to the wild-type strain. To the best of our knowledge, the engineered strain exhibited the highest H2 production rate of 171 mmol liter-1 h-1 and specific H2 production rate of 237 mmol g-1 h-1 among CO-dependent H2-producing microbes studied to date.