Acetogenic coccoid spore-forming bacteria isolated from the rumen

Area of Science:

• Microbiology
• Rumen Microbiology
• Acetogenesis

Background:

• Acetogenic bacteria play crucial roles in anaerobic digestion and carbon cycling.
• The rumen microbiome is a complex ecosystem with diverse microbial communities.
• Previous research has not identified Gram-positive, spore-forming cocci capable of acetogenesis from H2 + CO2.

Purpose of the Study:

• To isolate and characterize novel acetogenic bacteria from ruminant animals.
• To investigate the phylogenetic, physiological, and morphological characteristics of these new isolates.
• To determine if these bacteria represent a new species within the Clostridium genus.

Main Methods:

• Isolation of bacteria from rumen contents of lambs, llamas, and bisons.
• Cultivation using H2 + CO2 as the sole energy source.
• Detailed characterization including DNA G+C content, optimal growth conditions (temperature, pH), substrate utilization, and 16S rRNA gene sequencing.
• Phylogenetic analysis based on 16S rRNA gene sequences.

Main Results:

• Thirteen strains of a novel acetogenic bacterium were isolated.
• The bacteria are Gram-positive, coccoid, spore-forming, and form chains.
• They efficiently utilize H2 + CO2 to produce acetate, likely via the acetyl-CoA pathway.
• Optimal growth occurred at 37-40°C and pH 6.3-6.8.
• The organism demonstrated heterotrophic utilization of various organic substrates.
• DNA G+C content was 46.5 mol%.
• 16S rRNA gene sequencing and phylogenetic analysis indicated significant divergence from known species.

Conclusions:

• The isolated bacteria represent a new species, distinct from previously described acetogens.
• These findings expand the known diversity of acetogenic bacteria in the rumen.
• The unique characteristics warrant further taxonomic investigation and potential reclassification within the Clostridium genus.