Molecular characterization of midgut bacteria of Aedes albopictus exhibiting swarming motility property

Aedes mosquitoes are responsible for the transmission of arboviruses including dengue, chikungunya, zika, and yellow fever throughout the world. Mosquito gut harbors a variety of microbes, known to play a potential role in various physiological processes such as food digestion and pathogen development. Many bacterial species exert various movements like swarming, gliding and twitching which vary with individual bacterial species. Swarming is one of the movement patterns of bacterial cells in which newly growing cells direct themselves towards the edges of the colony on the solid agar plate. We have isolated a bacterial colony, which exerts swarming activity and moves away from its inoculation point following a translucent path. After repeated sub-culturing of the colony we isolated two different bacterial species which were found to be highly associated to each other in co-culture. Various techniques like biochemical analysis, 16S rRNA gene sequence based analysis, MALDI-TOFF MS and Scanning Electron Microscopy (SEM) were applied for in-depth characterization of isolates. The isolates were identified as Staphylococcus saprophyticus and Brevibacillus agri. Both bacterial isolates showed swarming activity in co-culture on the solid agar surface, but lost the activity when tested individually. Moreover, the swarming activity was even not recovered when both purified bacterial isolates were mixed at different concentrations. This demonstrated that an integral connection exists between the two species which is responsible for their swarming activity in co-culture.