Diversity analysis and functional role of insect gut bacteria

Abstract

In this report, the community structure of gut bacteria and their functional role in two different newlineinsects Helicoverpa armigera and Drosophila melanogaster were studied. H. armigera is an newlineimportant crop pest with increased resistance to major groups of pesticides while D. newlinemelanogaster is an experimental model system in biology. In the first study dealing with H. newlinearmigera, bacterial members of genus Bacillus, Paenibacillus, Cellulomonas, Acinetobacter, newlineMicrococcus, Enterobacter, and Enterococcus were isolated and identified. The culture newlineindependent molecular analysis also identified the presence of other bacterial candidates. TRFLP newlineanalysis revealed that the bacterial community of this insect is dependent on the host plant newlineon which it feeds. The strong similarity of the Acinetobacter, in the gut, to bacteria isolated from newlinexenobiotic degrading ecosystems suggested its putative role in metabolizing insecticides. newlineAcinetobacter not only was able to grow in the presence of quinalphos but was also able to newlinedegrade it efficiently. When grown in the presence of quinalphos, the esterase enzyme levels of newlinethis bacterial candidate increased significantly. Insects reared on Acinetobacter, displayed higher newlineesterase levels and low susceptibility to quinalphos while the axenic insects succumbed to the newlinetoxicity of quinalphos. newlineBacterial members of genus Enterobacter, Pantoea and Enterococcus were isolated and newlineidentified from D. melanogaster midgut. Culturable method divulged differences in the bacterial newlineflora between lab reared and wild collected males and females. An effort was made to understand newlinethe roles played by this resident gut microflora in shaping the development of an insect by newlinegrowing Drosophila melanogaster flies in Caltech half diet (HD). It was found that in the newlineabsence of microbes, the D. melanogaster flies raised in HD medium show delayed and lower newlinepupation, eclosion, fecundity and feeding rates, along with a decrease in size of larvae, pupae newlineand adults than their non-sterile HD