Taxonomy of the marine, luminous bacteria

Abstract

One hundred and seventy-three strains of marine, luminous bacteria isolated from sea water, surfaces and intestines of fish, as well as from the luminous organs of fish and squid were submitted to an extensive phenotypic characterization. A numerical analysis of the results grouped these strains into four clusters which were formed on the basis of overall phenotypic similarity. One cluster, which was given the designation Beneckea harveyi, consisted of strains which had a moles % GC content in their DNAs of 46.5 ± 1.3 and a single, sheathed, polar flagellum when grown in liquid medium. Most of these strains had unsheathed, peritrichous flagella in addition to the sheathed, polar flagellum when grown on solid medium. The two phenotypically similar clusters which were assigned the species designations Photobacterium phosphoreum and f. mandapamensis consisted of strains which had 1-3 unsheathed, polar flagella and moles % GC contents in their DNAs of 41.5 t 0.7 and 42.9 t 0.5, respectively. The cluster designated f. fischeri contained strains having 2-8 sheathed, polar flagella and a moles % GC content of 39.8 t 1.1. These four species could be further distinguished on the basis of a number of nutritional properties as well as other phenotypic traits. The assignment of the luminous, marine bacteria to four species was supported by differences in the properties of the luminous system as well as differences in the pattern of regulation of aspartokinase activity which are discussed. The species B. harveyi was found to be phenotypically similar to a number of previously characterized, non-luminous strains of Beneckea which shou1d probably be assigned to this species.