Study of the toxicity of Bacillus cereus on silkworm (Bombyx mori) and the relevant proteome

Twenty-six strains of bacteria were obtained by random sampling previously in our lab. The most pathogenic strains were identified as Bacillus cereus through toxicity assessment of silkworm. Silkworm larvae were killed within 12 h of injection of B. cereus. The changes in cytoplasm and cell membrane caused by the infection were observed by Histopathological examination; these were obvious at 6 - 10 h after injection of the bacteria, indicating its acute pathogenicity. The differential protein spots of silkworms in the treatment group and control group were detected by two-dimensional electrophoresis. Five kinds of silkworm protein were identified in fat body tissue; of these, four proteins were up-regulated and one was down-regulated. Thirteen silkworm proteins were detected in midgut tissues; of these, six proteins were up-regulated and expression of seven proteins was down-regulated. After biological analysis, a 14-3-3zeta protein was expressed in both tissues, and several other up-regulated proteins were found to be involved in the anti-inflammatory, immune, phagocytotic and metabolic pathways of the body, indicating that the host had an emergency response to B. cereus injection. The down-regulated proteins were associated with cell biofilm stability, signal transduction and detoxification, respectively. The protein expression was verified by fluorescence quantitative PCR. The results showed that the expression of proteins was consistent with the changes in gene expression.