| Bactrocera dorsalis Hendel is a polyphagous, cosmopolitan and invasive pest at home and abroad, and it can infect fruits, vegetables and flowers of more forty families and two hundred-fifty species, such as mangoes, oranges, tangerines, carambolas, guavas and sorts of gourds. In our study, we investigated the diversity of the intestinal bacteria community of the gut of adult B. dorsalis, the structure of the cultured bacterial community, the attraction function of cultured bacteria and it's influence to host's mortality and longevity. These results contributed to explore intestinal bacteria on the impact of the physiological function and ecological significance of B. dorsalis, to understand coevolution between B. dorsalis and its symbiotic bacteria, and to provide new knowledge for species evolution ways. Further studies will be focused on identifying the function of each representative species and establishing whether these species could play important roles in the future as biocontrol agents.In this study, we employed traditional culture techniques and PCR-DGGE molecular methods to study the diversity of the intestinal bacteria community and the structure of the culturable bacterial community of adult B. dorsalis from three different populations (lab-reared (LR), lab sterile sugar-reared (LSSR) and field-collected (FC)). We also studied the attraction function of intestinal cultured bacteria to adult B. dorsalis and it's influence to host's mortality and longevity. The main results were shown as follows:150 different DGGE profiles of bacteria clones were obtained from the adult gut of all three populations of B. dorsalis. By sequence similarities and phylogenetic analyzing, seven major phyla of bacteria were observed. These bacteria respectively belonged to Gammaproteobacteria, Actinobacteria, Alphaproteobacteria, Deltaproteobacteria, Bacteroidetes,. Flavobacteria and Firmicutes. In all three populations, Gammaproteobacteria which was the preponderant bacterium in the gut represented 70% of the total clones. Besides this phylum, the following phyla were judged to be major components of each population since they constituted 10% or more of the total clones of a given population:Actinobacteria (10.1%) was the major component of LR and Firmicutes (12.3%) was the major component of FC. Flavobacteria, Deltaproteobacteria, Bacteroidetes, and Alphaproteobacteria appeared in various populaitons with a few clones (less than 8 per phylum). Among the 150 sequences of bacterial 16S rDNA, three distinct clusters were identified (labeled as unclassified groups). This was the kind of microbial flora which presents lacking of knowledge, might be related to the special microenvironment of B. dorsalis gut. The closely related sequences (>97% sequence similarity) which had been retrieved from three populaitons were grouped as one common species. Three oriental fruit fly populations shared common representatives of the Enterobacteriaceae, including Klebsiella, Citrobacter, Enterobacter, Pectobacterium, and Serratia. According to the analysis of diversity indices, phylotype composition and phylogenetic distribution of the 16S rDNA clones, we found that the bacterial communities of three populations were significantly different from each other. The LSSR populaiton was the least diverse and had fewer phylotypes in common with the other libraries, whereas the populaitons of LR and FC were relatively more diverse.600 cultured bacteria in the intestinal tract of adult B. dorsalis from three populations were classified into 53 unique phylotypes. All sequenced bacteria strains were grouped into three families:Enterobacteriaceae, Enterococcaceae and Bacillaceae. The Enterobacteriaceae was dominated in all the populations (72.0%-82.5%). The closely related sequences (>97% sequence similarity) which had been retrieved from culturable bacteria of three populaitons were grouped as one common species. By colony morphology, physiological and biochemical characteristics test, we determined the common species:five strains of bacteria as Enterobacter, two strains of Klebsiella, one strain of Citrobacter, one strain of Pantoea, two strains of Enterococcus, and four strains of Bacillus.The attractancy bioassays results in the laboratory showed that all bacteria strains were significantly more attractive to B. dorsalis adults than the tryptic soy broth control. Among them, Bacillus cereus, Enterococcus faecalis, Enterobacter cloacae and Citrobacter freundii were the most attractive bacteria. The autoclaved supernatants were significantly more attractive than the filtered supernatants or whole beer. Furthermore, the results of the field test showed that the six bacteria strains were significantly more attractive than the control. B. cereus and E. faecalis caught significantly more males, females, and males+females than any other of the bacterial metabolites. All the baits except Klebsiella oxytoca caught more females than males. These results were consistent with that of laboratory bioassays.By feeding bacterial suspension solution, we assessed the effect of the dominant Enterobacteriaceae community and the minor Bacillus community on the oriental fruit fly's survival and longevity. The results showed that fly longevity (of both males and females) was not affected by the presence of antibiotics. Ingestion of bacteria significantly affected mortality rate and average fly longevity in both sexes, regardless of previous exposure to antibiotics. In general, feeding on Bacillus had a negative effect on longevity, while feeding on the Enterobacteriaceae mixture had a beneficial effect. Compared to flies fed on sugar alone, flies fed on Bacillus died at a significantly faster rate and their average longevity was significantly reduced. Conversely, flies fed on Enterobacteriaceae died more gradually and lived significantly longer, on average, than flies fed on sugar.
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