The Genus Alteromonas and Related Proteobacteria
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The Genus Alteromonas and Related Proteobacteria VALERY V. MIKHAILOV, LYUDMILA A. ROMANENKO AND ELENA P. IVANOVA
Introduction Many marine heterotrophic Gram-negative aerobic or facultatively anaerobic bacteria are affiliated to the genera Alteromonas, Pseudoalteromonas, Glaciecola, Idiomarina and Colwellia. They belong to the γ-subclass of the class Proteobacteria (Stackebrandt et al., 1988) and share similar phenotypic, genotypic and phylogenetic characteristics. These bacteria, essential components of the marine part of the biosphere, have very diverse habitats including coastal and open water areas, deep-sea and hydrothermal vents, and marine sediments. The genus Alteromonas was created by Baumann et al. (1972) for marine Gram-negative heterotrophic bacteria motile by a single polar flagellum, with an oxidative metabolism and a DNA G+C content of 38–50 mol%. On the basis of 16S rDNA gene sequence analysis, the genus Alteromonas was revised in 1995 to contain only one species, A. macleodii. The remaining species were reclassified as Pseudoalteromonas species (Gauthier et al., 1995). The genus Glaciecola was proposed by Bowman et al. (1998c) for two groups of psychrophilic, strictly aerobic chemoheterotrophic bacteria isolated from sea-ice diatom assemblages from coastal area of eastern Antarctica. Two deep-sea bacteria were isolated from seawater of the Pacific Ocean and described as species of the new genus Idiomarina (Ivanova et al., 2000b). Deming and coauthors accommodated facultatively anaerobic, psychrophilic and barophilic bacteria into the genus Colwellia (Deming et al., 1988). Recently a new genus, Thalassomonas, comprising marine pigmented bacteria that are phylogenetic neighbors of Colwellia was described by Macian et al. (2001).
History of the Alteromonas and Pseudoalteromonas Genera Through 1994 In the 1950s, marine aerobic heterotrophic Gramnegative and nonfermentative Pseudomonas-like
bacteria with the low DNA G+C content of 40– 50 mol% were assigned to the genus Pseudomonas, including P. atlantica, P. carrageenovora (Humm, 1946; Yaphe, 1955; Yaphe, 1957), P. putrefaciens (Lee et al., 1981) and P. piscicida (Bein, 1954; Buck et al., 1963). The numerical taxonomy and some identification schemes of marine Pseudomonas-like bacteria have been considered in a number of studies (Shewan et al., 1960; Gibson et al., 1977; Lee et al., 1977; Gray and Stuart, 1980; Oliver, 1982). In 1972, Baumann and coauthors characterized 218 marine bacterial strains isolated from seawater samples collected in the area of the Hawaiian archipelago. Most of these bacteria were aerobic, Gram-negative and heterotrophic microorganisms, motile by a single polar flagellum. Bacteria with a DNA G+C content between 57.5 and 64.7 mol% were identified as members of the genus Pseudomonas. The remaining strains with a lower DNA G+C content (between 43 and 48 mol%) were affiliated to the genus Alteromonas. Four phenotypically distinguishable clusters were described
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