CULTURE CONDITIONS AFFECT CYTOTOXIN PRODUCTION BY SERRATIA-MARCESCENS

Cytotoxins have been implicated in the pathogenesis of bacterial infec tions. In this study, the influence of different culture conditions wa s evaluated on cytotoxin production by Serratia marcescens. Parameters such as culture media, incubation temperature, starting pH of culture medium, aeration, anaerobiosis, carbon sources, iron concentration in the culture media, and release of cell-bound toxin by polymyxin B wer e investigated. The data suggest that this cytotoxin is predominantly extracellular and is not induced by iron limitation. Aerobic culture w ith shaking resulted in higher cytotoxicity than static aerobic or ana erobic culture. Bacteria grown in glucose, sucrose or galactose were m ore cytotoxic than those grown in inositol or maltose. The culture con ditions that were identified as optimal for cytotoxin production by Se rratia marcescens were incubation temperature ranging from 30 to 37 de grees C, in medium adjusted to pH 8.5, with shaking. This work will co ntribute to further studies on the identification of this cytotoxic ac tivity.