Isolation and characterization of Sporomusa carbonis sp. nov., a carboxydotrophic hydrogenogen in the genus of Sporomusa isolated from a charcoal burning pile

With the description of Sporomusa ovata and Sporomusa, the genus Sporomusa was first mentioned in 1984 (1). Until now, seven other species were validly published under the ICNP. All members of the genus are able to grow on H₂ + CO₂, alcohols, N-methylated and methoxylated monoaromates. H₂ + CO₂ is converted via acetogenesis using the Wood-Ljungdahl pathway (WLP). Autotrophic growth on CO has only been reported for S. ovata (1) and Sporomusa termitida (2). Energy conservation during acetogenesis in the mesophilic genus Sporomusa is achieved by building a chemiosmotic H⁺-gradient using an Rnf complex, which is subsequently utilized by an ATP synthase for the phosphorylation of ADP to ATP. All Sporomusa strains contain both cytochromes b/c and ubiquinones (3). The presence of cytochromes and quinones is a rare trait of acetogens and besides Sporomusa members only present in acetogens of the thermophilic Moorella genus. Members of the genus Sporomusa are of interest for biotechnological applications.

A novel species, Sporomusa carbonis ACPt was isolated from the covering top soil of an active charcoal burning pile. In contrast to the other Sporomusa species this strain is not able to grow on H₂ + CO₂, but converts CO to H₂ + CO₂. This strain represents the first carboxydotrophic hydrogenogen within this genus. Phylogenomic analysis of showed that strain ACPt represented a novel species of the genus Sporomusa. The genome of ACPtT encoded cytochromes, ubiquinones, the Wood-Ljungdahl gene cluster and an Rnf complex, which were identified as common features all Sporomusa type strains.

Based on the genomic, morphological and physiological features presented in this study, strain ACPtT is proposed as a novel species in the genus Sporomusa with the name Sporomusa carbonis sp. nov. (DSM 116159^T and CCOS 2105^T).

1. Möller B, Oßmer R, Howard BH, Gottschalk G, Hippe H. Sporomusa, a new genus of gram-negative anaerobic bacteria including Sporomusa sphaeroides spec. nov. and Sporomusa ovata spec. nov. Arch Microbiol 1984;139:388–96. https://doi.org/10.1007/BF00408385.

2. Breznak JA, Switzer JM, Seitz HJ. Sporomusa termitida sp. nov., an H2/CO2-utilizing acetogen isolated from termites. Arch Microbiol 1988;150:282–8. https://doi.org/10.1007/BF00407793.

3. Rosenbaum FP, Müller V. Energy conservation under extreme energy limitation: the role of cytochromes and quinones in acetogenic bacteria. Extremophiles 2021;25:413–24. https://doi.org/10.1007/s00792-021-01241-0.