The Family Colwelliaceae

The family Colwelliaceae is part of the order Alteromonadales within the class Gammaproteobacteria and currently comprises the type genus Colwellia and the genus Thalassomonas. Collectively, Colwelliaceae encompasses at least 19 species. Both genera are strictly marine in terms of distribution and appear as curved to straight rod-shaped cells that form primarily nonpigmented colonies, possess a polar or subpolar flagellum, and are catalase and oxidase positive. Metabolism varies between the two genera, with Colwellia species being facultatively anaerobic and able to grow fermentatively and also by using at least nitrate as an electron acceptor. Most Thalassomonas species are instead strictly aerobic; however further study is required to confirm this. Both members of Colwelliaceae have attracted interest in terms of extremophilic environmental research and biotechnological investigations. The genus Colwellia contains several obligately psychrophilic (cold-requiring) and piezophilic (pressure-requiring) species that synthesize omega-3 polyunsaturated fatty acids while a number of Thalassomonas species possess potent agarolytic activity. The species Colwellia psychrerythraea represents a model for understanding how bacteria thrive at freezing temperatures.