Abstract

The present study investigated the physiological and genetical effects of non-pathogenic bacteria (G^-) Escherichia coli and entomopathogenic bacteria (G⁺) Bacillus thuringeinsis on the mulberry silkworm, Bombyx mori (Lepidoptera: Bombycidae). We used bioassay and molecular markers linked to 5^th instar larvae to inject bacterial and analyze the response of B. mori. Also, the effect of both bacteria on the total and differential haemocytes count of the 5^th instar larvae of B. mori was evaluated. Results revealed that injection with E. coli increased the total haemocytes counts (THCs) to about 59.09% of the control at 24 h post-infection. In this respect, B. thuringeinsis decreased the THCs by about 45.9, 58.39 and 69.4%, respectively, than control after 48 h post-infection at concentrations of 0.5, 1 and 1.5 ppm. Injection with E. coli increased the number of Pr, Pl, Gr and Oe. On the contrary, injection with B. thuringeinsis significantly decreased the number of Pr, Pl and Gr and Oe. The mutagenic effect of the bacterial injection produced and/or affected several proteins that killed or caused larval deformation through the alteration of the physiological and genetic processes.

Key words: Bombyx mori, haemocytes, corpora allata, DNA structure, Escherichia coli, Bacillus thuringeinsis.