Characterizations of Larval Gut Bacteria of Anopheles Subpictus Grassi and Their Role in Mosquito Development in Hooghly, West Bengal, India.

Malaria is a serious vector borne disease transmitted by different species of Anopheles mosquitoes. The present study was aimed to isolate & characterize the bacterial flora from the gut of An. subpictus larvae prevalent in Hooghly and explore their roles in host survival and development. Mosquito larvae and adults were collected from field and were maintained in laboratory. Bacterial load in the larval midgut was determined, predominant strains were isolated and characterized by polyphasic approach. Role of these bacteria in larval survival & development were assayed. Bacterial load in the gut of larvae was found to vary in field collected and lab reared mosquitoes in different seasons. Morphological, bio-chemical and molecular analysis explored four common bacterial isolates namely Bacillus subtilis , Bacillus pumilus , Bacillus cereus & Proteus vulgaris in the larval gut throughout the year. Larval survival rate was greatly reduced (0.06) & time of pupation was prolonged (17.8±0.57) in absence of their gut bacteria. Total tissue protein (7.78±0.56), lipid (2.25±0.19) & carbohydrate (16.5±0.79) contents of larvae and body weight & wing length of adult male (0.17±0.02 & 1.74±0.43) & female (0.19±0.02 & 1.99±0.46) mosquitoes were also found to be greatly reduced in the absence of gut bacteria. Developmental characteristics were restored with the introduction of culture suspension of all four resident gut bacterial isolates. Present study indicates that the mosquitoes solely depend on their gut bacteria for their survival & development. So, manipulation or control of this gut bacterial communities might inhibit survival & development of vector mosquitoes.