Characterization and identification of marine Alteromonas nigrifaciens strains and emendation of the description

Nine nonpigmented strains of gram-negative, aerobic, marine bacteria with polar flagella were isolated from the mussels Crenomytilus grayanus and Patinopecten jessoensis. These organisms were conspecific and exhibited relatively high levels of genetic relatedness (61 to 100%), The G+C contents of the DNAs of these strains were 38.5 to 40.2 mol%. The strains isolated from mussels were phenotypically distinct from previously described Alteromonas species that have similar DNA G+C contents (Alteromonas haloplanktis, Alteromonas tetraodonis, Alteromonas atlantica, and Alteromonas carrageenovora ), and their DNAs exhibited only 12 to 41% similarity with the DNAs of the type strains of these species. DNA-DNA hybridization data revealed that the levels relatedness between the strains which we studied and the type strain of Alteromonas nigrifaciens were significant (66 to 70%). Production of a melanin-like pigment, which is characteristic of A. nigrifaciens, was observed only in tyrosine-containing media. The strains isolated from mussels were identified as A. nigrifaciens, We present an emended description of A, nigrifaciens that includes several phenotypic and chemotaxonomic characteristics.