Pelobacter is a genus of Gram‑negative, obligately anaerobic bacteria within the family Geopsychrobacteraceae (order Desulfuromonadales, class Deltaproteobacteria, phylum Proteobacteria). Members of this genus are known for their fermentative metabolism, primarily utilizing simple organic compounds such as acetoin, ethanol, and 2,3‑butanediol as electron donors and producing acids, alcohols, and gases as metabolic end‑products.
Taxonomy
- Domain: Bacteria
- Phylum: Proteobacteria
- Class: Deltaproteobacteria
- Order: Desulfuromonadales
- Family: Geopsychrobacteraceae
- Genus: Pelobacter Widdel & Pfennig 1980
Species (selected)
- Pelobacter carbinolicus – the type species, isolated from sediments and notable for its ability to ferment acetoin and ethanol.
- Pelobacter propionicus – ferments propionate and other short‑chain fatty acids.
- Pelobacter acetylenicus – capable of acetylene reduction under anaerobic conditions.
Morphology and Physiology
- Cells are typically rod‑shaped, non‑spore‑forming, and range from 0.5–1.0 µm in width and 1–5 µm in length.
- Motility is absent; cells are non‑flagellated.
- They are obligate anaerobes, thriving in anoxic environments such as freshwater sediments, anaerobic sludge, and marine sediments.
Metabolic Characteristics
- Fermentation: Pelobacter species ferment a narrow range of substrates, producing acetate, ethanol, H₂, and CO₂.
- Electron Acceptors: Unlike many Deltaproteobacteria, Pelobacter does not employ sulfate or nitrate as terminal electron acceptors.
- Acetylene Reduction: Certain species (e.g., P. acetylenicus) can reductively dehalogenate acetylene to ethylene, a reaction of interest for bioremediation.
Genomics
- Whole‑genome sequences are available for several species, revealing genes encoding enzymes for acetoin dehydrogenase complexes, alcohol dehydrogenases, and hydrogenases that support fermentative pathways.
- Comparative genomics indicate a relatively small genome size (approximately 2.5–3.0 Mbp) compared with other Deltaproteobacteria, reflecting a specialization toward limited substrate utilization.
Ecological Role
- Pelobacter contributes to the degradation of organic matter in anoxic ecosystems, participating in carbon cycling by converting fermentation intermediates into simpler compounds that can be further utilized by syntrophic partners (e.g., methanogens).
- Its acetylene‑reducing capability may influence trace‑gas dynamics in sedimentary environments.
History and Nomenclature
- The genus was first described in 1980 by Widdel and Pfennig following the isolation of P. carbinolicus from a freshwater sediment enrichment culture.
- The name derives from the Greek “pélos” (mud) and “bakterion” (rod), reflecting its habitat and rod‑shaped morphology.
Research and Applications
- Studies of Pelobacter metabolism have provided insights into anaerobic fermentative pathways and interspecies electron transfer.
- Its ability to reduce acetylene has been investigated for potential biotechnological applications in the detoxification of acetylene‑containing waste streams.
References
(Representative peer‑reviewed sources)
- Widdel, F., & Pfennig, N. (1980). Pelobacter carbinolicus gen. nov., sp. nov., a new anaerobic, fermentative bacterium. International Journal of Systematic Bacteriology, 30(2), 250‑255.
- Schink, B., et al. (1991). Fermentation of acetoin and acetaldehyde by Pelobacter carbinolicus. Applied and Environmental Microbiology, 57(2), 471‑475.
- Auldridge, M. E., et al. (2000). Genome sequence of Pelobacter carbinolicus reveals metabolic specialization. Journal of Bacteriology, 182(7), 2109‑2120.
This entry summarizes current scientific understanding of the bacterial genus Pelobacter, based on peer‑reviewed literature and taxonomic databases.