f Intra- and Intergeneric Similarities of the rRNA Cistrons of Alteromonas, Marinomonas (gen. nov.) and Some Other Gram-negative Bacteria

Summary: 14C-labelled rRNA was prepared from Alteromonas macleodii ATCC 27126 and from Alteromonas haloplanktis ATCC 14393. 3H-labelled rRNA was isolated from Alteromonas vaga ATCC 27119 and Alteromonas putrefaciens ATCC 8071 colony type tl. These rRNAs were hybridized under stringent conditions with filter-fixed DNA from various Alteromonas strains and from organisms of marine origin and/or with mol % G + C values in the range 40 to 50. Each hybrid was described by its Tm(e) and percentage of rRNA binding. From rRNA similarity maps and Tm(e) dendrograms the following conclusions were drawn. The genus Alteromonas is very heterogeneous and consists of four rRNA branches: (1) Alt. macleodii alone; (2) the Alt. haloplanktis cluster, containing most of the named Alteromonas species and a number of organisms which should be renamed Alteromonas (“Pseudomonas marinoglutinosa”, “Pseudomonas nigrifaciens”, “Pseudomonas atlantica” ATCC 19262, “Pseudomonas carrageenovora”, “Pseudomonas piscicida”, and several unnamed alginolytic bacteria); we propose to limit the genus Alteromonas to the former two clusters; (3) Alt. putrefaciens, the rRNA cistrons of which resemble those of the Vibrionaceae and are as different from the above two Alteromonas rRNA branches as are those of the Vibrionaceae, the Enterobacteriaceae and Aeromonas; “Pseudomonas rubescens” belongs to this branch and Alteromonas hanedai seems to be a remote relative; (4) Alteromonas communis and Alt. vaga constitute another, separate rRNA branch; in conjunction with their special phenotypic features, we propose to create a new genus, Marinomonas, for them. The exact taxonomic position of “Alteromonas thalassomethanolica” could not be established.