CHARACTERIZATION AND IDENTIFICATION OF MARINE ALTEROMONAS-NIGRIFACIENS STRAINS AND EMENDATION OF THE DESCRIPTION

Nine nonpigmented strains of gram-negative, aerobic, marine bacteria w ith polar flagella were isolated from the mussels Crenomytilus grayanu s and Patinopecten jessoensis. These organisms were conspecific and ex hibited relatively high levels of genetic relatedness (61 to 100%), Th e G+C contents of the DNAs of these strains were 38.5 to 40.2 mol%. Th e strains isolated from mussels were phenotypically distinct from prev iously described Alteromonas species that have similar DNA G+C content s (Alteromonas haloplanktis, Alteromonas tetraodonis, Alteromonas atla ntica, and Alteromonas carrageenovora ), and their DNAs exhibited only 12 to 41% similarity with the DNAs of the type strains of these speci es. DNA-DNA hybridization data revealed that the levels relatedness be tween the strains which we studied and the type strain of Alteromonas nigrifaciens were significant (66 to 70%). Production of a melanin-lik e pigment, which is characteristic of A. nigrifaciens, was observed on ly in tyrosine-containing media. The strains isolated from mussels wer e identified as A. nigrifaciens, We present an emended description of A, nigrifaciens that includes several phenotypic and chemotaxonomic ch aracteristics.