Methylobacterium sp. isolated from the midgut of Anopheles stephensi inhibits egg maturation in host ovary

The gut bacteria of insects are associated with digestion, nutrition, and reproduction. The midgut bacteria of Anopheles mosquitoes have been examined predominantly for their effects on the transmission of Plasmodium parasites. However, the effects of midgut bacteria on Anopheles mosquitoes have not been studied. In this study, we investigated the effects of midgut bacteria on adult female An. stephensi mosquitoes. These mosquitoes were fed antibiotics mixed with 10% sucrose for 2 weeks to alter the composition of their midgut bacteria. The results showed that the mosquitoes fed with streptomycin (ST) or kanamycin (KM) showed inhibited egg maturation 2 days after blood feeding. Methylobacterium sp. was the predominant bacterium in the midgut of mosquitoes fed KM or ST for 2 weeks (ST/2 weeks). Mosquitoes that were fed suspensions of Methylobacterium sp. isolated from the midgut of ST/2 weeks after blood feeding for 3 days showed inhibited egg maturation. Furthermore, egg maturation was inhibited in mosquitoes that were fed supernatant and precipitate obtained by boiling and centrifuging Methylobacterium sp. suspension. Thus, this study demonstrated that Methylobacterium sp. isolated from the midgut of An. stephensi mosquitoes after blood feeding inhibited egg maturation.