A bacterial strain BGI-1 was isolated from the gut of German cockroaches (Blattella germanica L.) and was identified as Bacillus subtilis based on 16S rDNA sequence and morphological, physiological, and biochemical characters. The strain BGI-1 inhibited the growth of Beauveria bassiana; the diameter of the inhibition zone exceeded 30 mm. Vesicles were observed in B. bassiana hyphae on the edge of the inhibition zone. Fermentation of BGI-1 reduced the conidial germination rate by 12%. Further studies demonstrated that B. bassiana infections in German cockroaches orally treated with the extracts of BGI-1 fermentation were significantly weakened. Cumulative mortality rate was 49.5% in the treatment group at the 20 d, while that of the control group was 62.3%. The study intends to understand the relationship between the intestinal flora and the cockroach. Those microbes with anti-entomopathogenic fungi activity might contribute to resisting the infection of pathogenic fungi.

A proteomic approach combining two-dimensional polyacrylamide gel electrophoresis and tandem mass spectrometry was used to compare hemolymph expression profiles of a beta-cypermethrin-resistant Blattella germanica L. strain and a beta-cypermethrin-susceptible strain. Twenty-eight hemolymph proteins were differentially expressed in the resistant cockroach strain; 19 proteins were upregulated and 9 proteins were downregulated compared with the susceptible strain. Protein identification indicated that expression of putative cuticular protein, nitric oxide synthase, triosephosphate isomerase, alpha-amylase, ABC transporter, and Per a 3 allergen was elevated, and expression of arginine kinase and glycosidase was reduced. The differential expression of these proteins reflects the overall change in cellular structure and metabolism related to the resistance of pyrethroid insecticides.