Molecular Diversity And Physiological Role Of The Gut Bacterial Communities In Bactrocera Minax

Bactrocera minax is a serious pest that infests Citrus genus plants, which occurs one generation for one year. It is mainly distributed in central and southwestern provinces in China. Currently the lack of artificial rearing of B. minax has impeded the study and management of this Tephritid fly. To improve the method of artificial rearing of B. minax, we identified the diversity of gut bacteria in B. minax, and investigated the culturable bacterial community and the physiological role of intestinal bacteria to adults and larvae. The main results were as follows:1. We studied the molecular diversity of intestinal bacterial community of different developmental stages of B. minax using 454 pyrosequencing technology. Some bacterial groups presented in all developmental stages of B. minax and these bacteria were dominant species of each developmental stage. They may vertically transmit across different developmental stages. These bacteria related to Enterobacter, Providencia Lactococcus, Kluyvera, unclassified Enterobacteriaceae and Streptophyta.The first, second and third-instar larvae of B. minax had some bacterial groups in common and these bacteria were dominant populations in each developmental stage. They may have a significant impact on the development of the larvae. These bacteria related to Enterobacter, Providencia, Lactococcus, Kluyvera, Pantoea, Methylobacterium, Streptophyta and unclassified Enterobacteriaceae.The intestinal bacteria composition of different developmental stages of B. minax had not only similarity but also difference. Difference was closely related to intestinal environment of different developmental stages of B. minax. The characteristic bacterial populations of first-instar larvae and egg were Delftia and Serratia. Morganella was the the characteristic bacterial populations of the pupae. The characteristics bacterial populations of female adults and male adults of B. minax was Kluyvera.2.Using 16S rRNA-ARDRA analysis, colony morphology, Physiological and biochemical characteristic tests, we identified the intestinal culturable bacteria of adults and second-instar larvae of B. minax. The dominant species of the intestinal culturable bacteria of the adults were Klebsiella oxytoca and Citrobacter freundii. The dominant species of the intestinal culturable bacteria of the second-instar larvae were Klebsiella oxytoca and Enterobacter hormaechei. The same cultured bacteria species of B. minax adults and second-instar larvae was Klebsiella oxytoca. The bacteria may vertically transmitt across different developmental stages.3.The culturable bacteria were isolated from the gut of B. minax adults. The presence of antibiotics in the diet had no significant effects on the longevity both for male and female adults. The addition of antibiotics in the full diet significantly decreased the average number of copulations and eggs laid by females. Microorganisms may provided nutrients to adults or contribute to the absorption and utilization of nutrients of the adults.The presence of bacteria in the sugar diet had no significant effect on the longevity both for male and female adults. The addition of Klebsiella oxytoca in the sugar diet significantly increased the average number of copulation. The addition of bacteria in the sugar diet improved the fecundity of adults, however, feeding a single bacteria was not sufficient to fully compensate for the lack of nutrition in the sugar diet.4.The culturable bacteria were isolated from the gut of B. minax second-instar larvae. Larval survival, pupal weight and pupal length varied significantly among treatments. Larvae fed the natural food had the highest larval survival, heaviest pupal weight and longest pupal length compared with the artificial diet and the artificial diet plus antibiotics. The results showed natural food was better than the artificial diet and was more conducive to the development of the larvae. No significant differences were observed for larval survival, pupal weight, pupal length and pupal width between the treatment that the larvae fed the artificial diet and the artificial diet plus antibiotics. The development of B. minax larvae was influenced by the addition of antibiotics, but the difference was not significant under the artificial diet.The above results will improve the artificial rearing of B. minax in the laboratory effectively, which also pave the way for further study and management of B. minax.