Temperature dependent siderophore production in Vibrio salmonicida

Vibrio salmonicida is the causative agent of cold water vibriosis, a haemor rhagic septicaemia of Atlantic salmon (Salmo salar). The disease is observe d only at low water temperatures and not normally above 10 degreesC. Sidero phore production and iron regulated outer membrane protein expression was s tudied at various temperatures. Although in iron-limited media optimal cell growth was identified at 12 degreesC, significant quantities of a single h ydroxamate siderophore were produced only at 10 degreesC or below. Dependen t on inoculant size, good growth without significant siderophore production was also observed in iron-limited media at temperatures above and below 10 degreesC. It is therefore likely that V salmonicida also possesses one or more non-siderophore based iron assimilation systems. Expression of high mo lecular weight iron-regulated outer membrane proteins appeared to be suppre ssed at 15 degreesC compared to expression at 6 and 10 degreesC. It is prop osed that temperature sensitive iron sequestration may constitute a signifi cant virulence factor in V salmonicida and may have implications for vaccin e manufacture. (C) 2001 Academic Press.