2006 Volume 21 Issue 1 Pages 36-43
SEp22, identical to Salmonella Dps, is a pathogenicity-related protein which we have isolated from the virulent Salmonella enterica subsp. enterica serovar Enteritidis (SE) from poultry farms. SEp22 is produced at the stationary phase, and rapidly lost upon incubation in fresh medium in vitro1). In this study, we examined the effects of nutrients in the medium on the regulation of SEp22 expression. While Luria-Bertani (LB) medium induced the production of a large amount of SEp22 during culture overnight, M9 minimal medium had little or no effect. Addition of LB to M9 dose-dependently increased the amount of SEp22 produced, showing the requirement of certain nutrients in LB medium for the induction. It also suggests that simply entering the stationary phase from a growth phase is insufficient for the expression of SEp22 in a nutrient-poor medium like M9, contrary to the induction of Dps in nutritionally starved Escherichia coli (E. coli). A similar requirement of LB nutrients was observed during the rapid production of SEp22 in a logarithmic phase of growth in Salmonella treated with H2O2. On the other hand, no difference was observed between M9 and LB medium in the effect to decrease the amount of SEp22 accumulated during reincubation. These results show the importance of culture nutrients not in the breakdown but in inducing the expression of SEp22 in pathogenic SE.