Microbial Biodiversity within the Vibrionaceae

1. The Vibrionaceae 1.1. A GENERAL DESCRIPTION Vibrio takes its name from the Latin word Vibrare, meaning 'to wave'. Otto Müller first used the word Vibrio as a descriptor in the 18 th century to describe bacteria with an elongated shape observed in culture (Rossello-Mora and Amann 2001). The family Vibrionaceae, first described by Véron (1965), resides within the g-proteobacteria, one of the five subdivisions of the phylum Proteobacteria within the domain Bacteria. All Proteobacteria are gram negative. This extremely metabolically diverse group of bacteria of medical and industrial importance has been divided into five subdivisions (a, b, d, g, and e) on the basis of 16S rRNA sequence data. The g-Proteobacteria are divided into three major subgroups, denoted g-1, g-2, and g-3. Members of the g-1 and g-2 subgroups contain sulfur producing photosynthetic bacteria and members of the family Legionella, respectively. The g-3 subgroup consist of a " potpourri " of organisms, including oceanospirilla, many pseudomonads, the enterics, and the Vibrionaceae (Woese et al. 1985). Vibrionaceae is one of 22 families within the 14 orders of the g-Proteobacteria. Members of this family were first described as oxidase-positive, motile bacteria with polar flagella (Krieg and Holt 1984). More recent data demonstrate that all Vibrionaceae species are either straight or curved rods, with some species not having oxidase-positive phenotypes (Vibrio metschnikovii, V. gasogenes, Photobacterium phosphoreum, P. angustum, and some strains of P. leiognathi are oxidase-negative), and some being non-motile. Vibrionaceae currently contains six genera: Vibrio, Allomonas, Enhydrobacter, Listonella, Photobacterium and Salinivibrio. Each genera has its own distinguishing morphological and physiological characteristics (Krieg and Holt 1984). Phenotypic data used to define each genus are G/C content, the presence of sheathed polar flagella, requirement of sodium for growth, lipase activity, D-mannitol utilization, and sensitivity to vibriostatic compound 0/129 (Holt et al. 1994). The most recent online version (July, 2002) of Bergey's Taxonomic Outline lists 72 species of Vibrio, 7 of Photobacterium, 3 of Listonella, and one of the other three genera (Table 1). These facultative anaerobes are found almost exclusively in aquatic environments, and have G/C contents ranging from 38-66% (Krieg and Holt 1984).