Physiological Responses to Stress in the Vibrionaceae

1. The Vibrionaceae 1.1. A GENERAL DESCRIPTION The family Vibrionaceae (Domain Bacteria, Phylum Proteobacteria, Class Gammaproteobacteria) is comprised of mostly motile gram-negative chemoorganotrophs, possessing at least one polar flagellum (Farmer III and Janda, 2005; Thompson and Swings, 2006). Vibrios are facultative anaerobes, having both respiratory and fermentative metabolisms, and the mol% G+C of the DNA is 38-51% (Farmer III and Janda, 2005). Cells are usually 1 µm in width and 2-3 µm in length, and most are oxidase positive. The vast majority of vibrios require Na + for growth and survival, usually 0.5-3% NaCl for optimum growth. Additionally, most species are susceptible to the vibriostatic agent 0/129 (Thompson and Swings, 2006). In recent years, a two-chromosome configuration, one large and the other small (both circular), has been discovered to be a universal feature for all members of the Vibrionaceae (Iida and Kurokawa, 2006). The Vibrionaceae are ubiquitously distributed throughout aquatic habitats, freshwater and marine waters (Madigan and Martinko, 2006), including rivers, estuaries, lakes, coastal and pelagic oceanic waters, the deep sea, and saltern ponds (Urakawa and Rivera, 2006). Although as many as eight genera have been assigned to the Vibrionaceae, the two most specious are Vibrio and Photobacterium (Thompson and Swings, 2006). A third genus, Salinivibrio is worthy of mention due to its unusual ability to grow in a wide range of salinity (0-20% NaCl; Ventosa, 2005) and temperature (5-50°C; Bartlett, 2006) (refer to Table 1.). Numerous species are pathogenic and cause disease in aquatic animals and humans (Farmer III et al., 2005), Vibrio cholerae being the most notorious example as the causative agent of cholera (Colwell, 2006). V. vulnificus and V. parahaemolyticus can also cause severe illness in humans as a result of consuming contaminated seafood cause substantial economic losses to the aquaculture industry worldwide.