Effects of cofD gene knock-out on the methanogenesis of Methanobrevibacter ruminantium

This study aimed to investigate the effects of cofD gene knock-out on the synthesis of coenzyme F₄₂₀ and production of methane in Methanobrevibacter ruminantium (M. ruminantium). The experiment successfully constructed a cofD gene knock-out M. ruminantium via homologous recombination technology. The results showed that the logarithmic phase of mutant M. ruminantium (12 h) was lower than the wild-type (24 h). The maximum biomass and specific growth rate of mutant M. ruminantium were significantly lower (P < 0.05) than those of wild-type, and the maximum biomass of mutant M. ruminantium was approximately half of the wild-type; meanwhile, the proliferation was reduced. The synthesis amount of coenzyme F₄₂₀ of M. ruminantium was significantly decreased (P < 0.05) after the cofD gene knock-out. Moreover, the maximum amount of H₂ consumed and CH₄ produced by mutant were 14 and 2% of wild-type M. ruminantium respectively. In conclusion, cofD gene knock-out induced the decreased growth rate and reproductive ability of M. ruminantium. Subsequently, the synthesis of coenzyme F₄₂₀ was decreased. Ultimately, the production capacity of CH₄ in M. ruminantium was reduced. Our research provides evidence that cofD gene plays an indispensable role in the regulation of coenzyme F₄₂₀ synthesis and CH₄ production in M. ruminantium.