The Intestinal Bacterial Flora Community Structure Of Anopheles Sinensis Mosquitoes (Diptera:Culicidae)

Anopheles sinensis (Diptera: Culicidae) mosquito, is a major insect-vector in Asia and other parts of the world. Of the Anopheline mosquitoes present in China, A. sinensis is the most common and widely distributed species. Despite lots of studies that have been carried out on control of anopheles mosquitoes, malaria parasites remain a leading cause of morbidity and mortality of humans in Asia and Africa. Limitations of actual control by chemical insecticides, with several descriptions of pest resistance, have led to the search for new and innovative control strategies. However, despite the number of studies that have been conducted on gut bacterial flora, information are still lacking on the bacteria diversity occurring in the intestinal tracks of A. sinensis mosquitoes. In our study, we described the intestinal bacterial community structure (pre-blood meal and after blood-meal) of adult A. sinensis mosquitoes obtained from laboratory colonies and from different geographical parts of China, and explored the influence of microbial medium on the oviposition behavior of female A. sinensisAfter blood feeding for 24 h, the number (cfu) of midgut and hindgut bacteria increased 18.6-folds and 14.3-folds, respectively than pre-blood meal (Table 2). Before blood meal,3 major classes Gammaproteobacteria, Alphaproteobacteria and Bacilli were identified, whereas after-blood meal, only one class: Gammaproteobacteria counts was augmented. It was also observed that after blood meal, the population of Enterobacteriales, Aeromonadales, and Pseudomonadales groups in the midgut increased dramatically, while the population of Vibrionales, Rhodospirillales, Actinomycineae, Bacillales, and Lactobacillales declined. The highest value of diversity indices of gut bacterial communities of different developmental stages is 0.960 from 4 instars, and The minimum value is 0.789 from adult female pre-blood.A total of 1641 bacterial colonies were isolated from eight wild populations. The clones were distributed into 5 classess (Gammaproteobacteria, Betaproteobacteria, Alphaproteobacteria, Actinobacteria, and Bacilli), and 24 species (or genus). The gut contained more stable bacterial community that was partly affected by external conditions. Enterobacter cloacae, Cedecea davisae, Serratia liquefasciens, Pseudomonas sp. and Acinetobacter sp. found in all gut samples, were permanent microflora in the midgut. Intestinal bacterial communities of adult female A. sinensis from 9 different populations has a lower variation among samples within populations than between populations.Knowledge of the influence of bacteria harbored by larval gut and habitat on oviposition behavior is essential for the development of effective vector control approaches. In this study, mosquitoes laid greater numbers of eggs on a substrate containing bacteria than on a sterilized substrate. In addition, microorganisms in larval habitats, may attract females via their emitting volatile substances, and may stimulate females laying eggs via touching with these insects. Bacteria was isolated and identified from larval gut and their individual effect on mosquito oviposition response was evaluated in laboratory bioassays. Of six bacterial strains evaluated in the oviposition bioassays (laboratory-reared mosquito), Enterobacteria cloacae, Serratia liquefasciens, Aeromonas spp., Pseudomonas spp., and Acinetobacter spp. play positive roles in oviposition behavior, and Cedecea davisae, however, plays a neutral role. Oviposition responses of wild-caught females to these bacteria displayed three different levels (followed in declining rank order by Aeromonas sp. and Acinetobacter sp.> E. cloacae and Pseudomonas sp.> S. liquefasciens and C. davisae). These results demonstrate that females are capable of selecting an oviposition site based on the microorganisms residing in larval guts and larval habitats. This study shows that certain bacteria have the potential to be used as an ideal ecofriendly approach for the control of mosquito by altering oviposition behavior of female.