Leigh and Wolfe formally describe Acetogenium kiwui, a newly discovered thermophilic bacterium, and establish the genus Acetogenium. This organism is an obligately anaerobic, nonsporeforming, nonmotile rod that produces acetic acid from various substrates including sugars, hydrogen, carbon dioxide, formate, carbon monoxide, and pyruvate. Phylogenetic analysis using 16S ribosomal RNA oligonucleotide cataloging confirmed that A. kiwui represents a distinct genus separate from previously known acetogens. Unlike thermophilic Clostridium species that form heat-resistant spores, Acetogenium members lack spore-forming capability. The organism has a gram-positive cell wall ultrastructure despite giving a negative Gram stain reaction and is catalase negative. The authors propose classifying Acetogenium within the family Propionibacteriaceae. The type strain is A. kiwui ATCC 33488 (DSM 2030), establishing the taxonomic foundation for this newly recognized thermophilic acetogenic bacterium.

Key findings

• Acetogenium kiwui is a newly identified thermophilic, anaerobic bacterium capable of producing acetic acid from multiple substrates including CO₂ and H₂
• Phylogenetic analysis using 16S rRNA cataloging demonstrated A. kiwui represents a distinct genus separate from all previously established acetogenic bacteria
• Acetogenium differs from other thermophilic acetogens by lacking heat-resistant spores and motility
• The organism is proposed for classification in the family Propionibacteriaceae despite not being phylogenetically related to all Propionibacterium species