Temperature dependent siderophore production in Vibrio salmonicida

Vibrio salmonicida is the causative agent of cold water vibriosis, a haemorrhagic septicaemia of Atlantic salmon (Salmo salar). The disease is observed only at low water temperatures and not normally above 10 degrees C. Siderophore production and iron regulated outer membrane protein expression was studied at various temperatures. Although in iron-limited media optimal cell growth was identified at 12 degrees C, significant quantities of a single hydroxamate siderophore were produced only at 10 degrees C or below. Dependent on inoculant size, good growth without significant siderophore production was also observed in iron-limited media at temperatures above and below 10 degrees C. It is therefore likely that V. salmonicida also possesses one or more non-siderophore based iron assimilation systems. Expression of high molecular weight iron-regulated outer membrane proteins appeared to be suppressed at 15 degrees C compared to expression at 6 and 10 degrees C. It is proposed that temperature sensitive iron sequestration may constitute a significant virulence factor in V. salmonicida and may have implications for vaccine manufacture.