Methanol Metabolism in the Cytochrome and Menaquinone-Containing Acetogen Moorella thermoacetica

Methanol derived from pectin degradation is common in oxic and anoxic sediments and is used by various aerobic and anaerobic microorganisms such as acetogenic bacteria or methanogenic archaea as a carbon and energy source. Acetogens use the Wood-Ljungdahl pathway to disproportionate methanol to CO₂ and acetate. Methanol metabolism has been studied primarily in mesophilic acetogens such as Acetobacterium woodii and Eubacterium callanderi, that do not have cytochromes or quinones. Moorella thermoacetica, the model organism for elucidation of acetogenesis, is a thermophilic, cytochrome- and quinone-containing acetogen which is commonly found in terrestrial soil. Here, we elucidated the physiology and bioenergetics of M. thermoacetica growing on methanol by performing physiological and biochemical experiments as well as genome-wide transcription analysis. Thereby, we identified genes and enzymes involved in acetogenesis from methanol. We will present a comprehensive model for carbon and energy flow from methanol to acetate and line out the bioenergetics of methanol-based acetogenesis in M. thermoacetica. Furthermore, we show that in the presence of DMSO as an alternative electron sink, no acetate is produced from methanol.