Abstract
Moritellaceae is a family that belongs to the order Alteromonadales within the class Gammaproteobacteria. It embraces the genera Moritella and Paramoritella. Currently seven species and one species are known in the genera Moritella and Paramoritella, respectively. All species were phenotypically characterized as halophilic facultative anaerobes and isolated from marine environments. The genus Moritella has been known to consist solely of psychrophilic species, while Paramoritella species is mesophilic. The difference of temperature adaptation between two genera within the same family is quite similar to the evolutionally pattern observed in the two genera, Colwellia and Thalassomonas, within the family Colwelliaceae. The 16S rRNA gene sequences indicate that both genera are related with 93 % similarity level. The entire family is phylogenetically closely related to the family Shewanellaceae. Moritella species have been isolated from seawater, sediment, and fish samples, which were collected only from cold marine environments. Moritella species have been studied as model microorganisms of low-temperature-adapted enzymes, piezophilic adaptation of marine bacteria to the deep sea, and an economically severe fish pathogen. Moritella species are also known as producers of polyunsaturated fatty acids (PUFAs) such as docosahexanoic acid (DHA). The genus Paramoritella is now comprised of a single species Paramoritella alkaliphila isolated from hard coral and marine sand from tropical marine environments. These two genera are clearly differentiated by their habitats, growth temperature properties, G + C mol%, and lower levels of 16S rRNA gene sequence similarity (<93 %).
