Definition
Colwelliaceae is a family of Gram‑negative, rod‑shaped bacteria within the order Alteromonadales of the class Gammaproteobacteria. Members of this family are primarily marine heterotrophs.
Overview
The family Colwelliaceae comprises several genera, including Colwellia, Thalassomonas, and Psychromonas, among others. These bacteria are commonly isolated from cold marine environments such as deep‑sea sediments, sea ice, and polar waters, but some species are also found in temperate oceans. They are aerobic or facultatively anaerobic and are capable of degrading a range of organic compounds, contributing to the marine carbon cycle. Certain species are psychrophilic, thriving at temperatures near 0 °C, while others are mesophilic.
Etymology / Origin
The family name derives from the genus Colwellia, which was named in honor of Dr. Rita R. Colwell, a prominent microbiologist known for her work on environmental microbiology and waterborne pathogens.
Characteristics
- Cell morphology: Straight to slightly curved rods, typically 0.5–1.0 µm in width and 1–4 µm in length; cells are motile via polar flagella.
- Gram stain: Negative, possessing a thin peptidoglycan layer and an outer membrane containing lipopolysaccharide.
- Metabolism: Predominantly chemoheterotrophic; many species oxidize carbohydrates, amino acids, and fatty acids. Some can reduce nitrate or utilize sulfur compounds under anaerobic conditions.
- Physiology: Many members are psychrophilic or psychrotolerant, exhibiting optimal growth at 4–15 °C. They are salt‑tolerant, requiring marine‑type concentrations of NaCl (typically 1–5 % w/v) for growth.
- Genomics: Genomic analyses reveal genes associated with cold adaptation, such as cold‑shock proteins, antifreeze proteins, and enzymes with high catalytic efficiency at low temperatures.
- Ecological role: Contribute to the degradation of organic matter in marine ecosystems, especially in cold and deep‑sea habitats; some isolates are involved in the breakdown of polysaccharides like chitin and alginate.
Related Topics
- Alteromonadales (order)
- Gammaproteobacteria (class)
- Marine microbiology
- Psychrophilic microorganisms
- Rita R. Colwell (scientist)
- Marine carbon cycling
References for further reading:
- Bowman, J.P. (2006). “The Family Colwelliaceae”. International Journal of Systematic and Evolutionary Microbiology.
- Deming, J.W., et al. (2006). “Phylogeny and Taxonomy of Marine Gammaproteobacteria”. Systematic and Applied Microbiology.
- Colwell, R.R., et al. (2000). “Microbial Ecology of Polar Sea Ice”. Nature.