Rapid climate change and excessive plastics utilization lead to irreversible negative impact on our planet as well as on human society. The main accelerator of climate change is emission of greenhouse gases, which emerge primarily during fossil-based production processes. An alternative and in the best-case CO₂-negative process is microbial gas fermentation with acetogens. Acetogens harbor enzymes of the Wood-Ljungdahl pathway, which enables this group of anaerobic bacteria to use gaseous and liquid single carbon molecules. Some recently reclassified Eubacterium callanderi strains are to date not well characterized but indicate high potential for gas fermentation due to a wide substrate spectrum and genetic accessibility (Flaiz et al., Microb Cell Fact). As E. callanderi should serve as a bio catalysator for recombinant production of the bioplastic poly-3-hydroxybutyrate (PHB) the metabolic and transcriptomic characteristics of different E. callanderi strains should be analyzed to build the basis for selection of the best suitable strain for gas fermentation. The metabolic and transcriptomic characteristics of the strains E. callanderi "FD" (DSM 3662), "Marburg" (DSM 3468) and "2A" (DSM 2593) were examined by growth experiments using glucose and different methanol concentrations. For optimization of transformation of E. callanderi the protocol of Leang et al. (Appl Env Microbiol) was varied. Heterotrophic growth experiments of the E. callanderi strains "FD", "Marburg", and "2A" with glucose as carbon source revealed the ability of the acetogen to perform chain elongation via the reverse β-oxidation, which enables the bacterium to produce butyrate, hexanoate and octanoate. Acetogenic growth of all strains using methanol as carbon source resulted in production of butyrate and hexanoate. Furthermore, the product spectrum of E. callanderi includes acetate, ethanol, and isobutyrate as well as butanol. Antibiotic resistance tests elucidated sensitivity of E. callanderi "Marburg" to thiamphenicol and tetracycline, E. callanderi "FD" and "2A" showed natural resistances. Consequently, E. callanderi "Marburg" was selected for recombinant PHB production. In conclusion the acetogenic species E. callanderi shows great potential as bio catalysator for gas fermentation as it has both a wide substrate and product spectrum and is genetically accessible. Due to sensitivity of E. callanderi "Marburg" to antibiotics, it is the best suitable strain for recombinant PHB production.