Comparative analysis of the in vivo and in vitro metabolites produced by the entomopathogen Beauveria bassiana

Abstract

Beauveria bassiana, like other insect mycopathogens, has evolved mechanisms to penetrate the insect exoskeleton via germ tubes and to replicate in the host hemocoel. Our initial studies have shown that biologically active metabolites released in the hemolymph during the vegetative growth phase of B. bassiana disrupt the host immune response and metamorphosis. These components cause an immediate reduction in filopodial-producing hemocytes and an increase in the level of serum phenoloxidase. Radiolabeling of tissues explanted from healthy versus infected larvae has demonstrated both the induction and repression of polypeptides in B. bassiana infected hemolymph. None of the polypeptides detected with 35S pulse labeling were responsible for the cytotoxic and insecticidal activities detected in infected hemolymph. Western blots of SDS gels containing chromatographic fractions from healthy and infected sera probed with both antibodies against B. bassiana cell homogenates and culture filtrates contained a complex of antigens. The results of lectin labeling and sodium periodate treatments suggested that carbohydrates were the major epitopes being recognized by both monoclonal and polyclonal probes. Key words: insect mycopathogen, Beauveria bassiana, fungal metabolites, entomopathogen, Spodoptera exigua.