Phenotypic, Chemotaxonomic and Genomic Characterization of a Novel Anaerobic Acetogen, Clostridium muelleri sp. nov. P21T Isolated from Old Hay

Abstract

Acetogens are a group of obligately anaerobic bacteria that use the Wood-Ljungdahl (acetyl-CoA) pathway for the production of acetyl-CoA from 2 moles of CO2. Acetyl-CoA is then converted to various acids and alcohols such as ethanol, butanol, hexanol, acetic, butyric and caproic acids using CO, CO2 and H2 or carbohydrates as the energy source. This particular metabolic process is key for the use of acetogens in syngas fermentation. Biofuels have been used since the late 19th century with fluctuations in its use due to the efficiency and cost-effectiveness of non-renewable energy sources. In recent years, the world has seen significant traction in decreasing the global carbon footprint by increasing the use of biofuels generated from renewable energy sources. A novel, Gram-positive staining, solvent-and-acid producing, strictly anaerobic rod belonging to the genus Clostridium, designated P21T, was recovered from an enrichment selecting for acetogens from a sample of old hay collected in Stillwater, Oklahoma. Genomic analysis confirmed the laboratory observations that strain P21T contains the genes encoding for the Wood-Ljungdahl pathway for acetogenesis as well as the genes required for acid and alcohol production. Additional phenotypic and chemotaxonomic characteristics of strain P21T showed consistencies with previous observations seen from its nearest neighbors Clostridium carboxidivorans P7T, Clostridium drakei SL1T and Clostridium scatologenes ATCC 25775T. The physiological and genomic analysis of strain P21T will be used to examine its future potential use for industrial purposes.