No effect of Bt Cry1Ie toxin on bacterial diversity in the midgut of the Chinese honey bees, Apis cerana cerana (Hymenoptera, Apidae)

Cry1Ie protein derived from Bacillus thuringiensis (Bt) has been proposed as a promising candidate for the development of a new Bt-maize variety to control maize pests in China. We studied the response of the midgut bacterial community of Apis cerana cerana to Cry1Ie toxin under laboratory conditions. Newly emerged bees were fed one of the following treatments for 15 and 30 days: three concentrations of Cry1Ie toxin (20 ng/mL, 200 ng/mL, and 20 μg/mL) in sugar syrup, pure sugar syrup as a negative control and 48 ng/mL imidacloprid as a positive control. The relative abundance of 16S rRNA genes was measured by Quantitative Polymerase Chain Reaction and no apparent differences were found among treatments for any of these counts at any time point. Furthermore, the midgut bacterial structure and compositions were determined using high-throughput sequencing targeting the V3-V4 regions of the 16S rDNA. All core honey bee intestinal bacterial genera such as Lactobacillus, Bifidobacterium, Snodgrassella, and Gilliamella were detected, and no significant changes were found in the species diversity and richness for any bacterial taxa among treatments at different time points. These results suggest that Cry1Ie toxin may not affect gut bacterial communities of Chinese honey bees.