Revisiting carbon monoxide metabolism in the Moorella genus and isolation of a novel Moorella species

Thermophilic acetogens hold great potential for syngas fermentation, as they efficiently convert CO and H₂/CO₂ into added-value chemical building blocks. Among these, Moorella species are the most studied, known for their versatility by growing autotrophically on C1 gaseous compounds and heterotrophically on sugars and organic acids. In this study, we isolated two novel thermophilic CO-utilising acetogens belonging to the genus Moorella: strain AZ13.I, representing a novel species, and strain AZ24.1, which is closely related to M. humiferrea. We further investigated CO metabolism in this genus and found that all Moorella species isolated to date can utilise CO, contradicting earlier reports suggesting that the type strains of M. humiferrea (DSM 23265^T) and M. mulderi (DSM 14911^T) were incapable of metabolising this substrate. Finally, based on genomic analyses at the genus level, we suggest that CO metabolism is a universal trait across all Moorella species.