Bactrocera dorsalis is one of the most economically important fruit flies around the world. In this study, 454 pyrosequencing was used to identify the bacteria associated with different developmental stages of B. dorsalis. At ≥ 97% nucleotide similarity, total reads could be assigned to 172 Operational Taxonomic Units belonging to six phyla. Proteobacteria dominated in immature stages while Firmicutes dominated in adult stages. The most abundant families were Enterococcaceae and Comamondaceae. The genus Comamonas was most abundant in pupae whereas completely absent in adults. Some identified species had low sequence similarity to reported species indicating the possibility of novel taxa. However, a majority sequence reads were similar to sequences previously identified to be associated with Bactrocera correcta, suggesting a characteristic microbial fauna for this insect genus. The type and abundance of different bacterial groups varied across the life stages of B. dorsalis. Selection pressure exerted by the host insect as a result of its habitat and diet choices could be the reason for the observed shift in the bacteria groups. These findings increase our understanding of the intricate symbiotic relationships between bacteria and B. dorsalis and provide clues to develop potential biocontrol techniques against this fruit fly.

The gut microbiome of insects directly or indirectly affects the metabolism, immune status, sensory perception and feeding behavior of its host. Here, we examine the hypothesis that in the oriental fruit fly (Bactrocera dorsalis, Diptera: Tephritidae), the presence or absence of gut symbionts affects foraging behavior and nutrient ingestion. We offered protein-starved flies, symbiotic or aposymbiotic, a choice between diets containing all amino acids or only the non-essential ones. The different diets were presented in a foraging arena as drops that varied in their size and density, creating an imbalanced foraging environment. Suppressing the microbiome resulted in significant changes of the foraging behavior of both male and female flies. Aposymbiotic flies responded faster to the diets offered in experimental arenas, spent more time feeding, ingested more drops of food, and were constrained to feed on time-consuming patches (containing small drops of food), when these offered the full complement of amino acids. We discuss these results in the context of previous studies on the effect of the gut microbiome on host behavior, and suggest that these be extended to the life history dimension.

Background: The gut bacteria of tephritid fruit flies play prominent roles in nutrition, reproduction, maintenance and ecological adaptations of the host. Here, we adopted an approach based on direct observation of symbiotic or axenic flies feeding on dishes seeded with drops of full diet (containing all amino acids) or full diet supplemented with bacteria at similar concentrations to explore the effects of intestinal bacteria on foraging decision and fitness of Bactrocera dorsalis. Results: The results show that intestinal probiotics elicit beneficial foraging decision and enhance the female reproduction fitness and survival of B. dorsalis (symbiotic and axenic), yet preferences for probiotic diets were significantly higher in axenic flies to which they responded faster compared to full diet. Moreover, females fed diet supplemented with Pantoea dispersa and Enterobacter cloacae laid more eggs but had shorter lifespan while female fed Enterococcus faecalis and Klebsiella oxytoca enriched diets lived longer but had lower fecundity compared to the positive control. Conversely, flies fed sugar diet (negative control) were not able to produce eggs, but lived longer than those from the positive control. Conclusions: These results suggest that intestinal bacteria can drive the foraging decision in a way which promotes the reproduction and survival of B. dorsalis. Our data highlight the potentials of gut bacterial isolates to control the foraging behavior of the fly and empower the sterile insect technique (SIT) program through the mass rearing.

Bacteria inhabiting the gut of insects provide many benefits to their hosts, such as aiding in food digestion, reproduction, and immunity, tissue homeostasis, adaptation to environment and resistance to pathogen and pesticides. The cowpea beetle, Callosobruchus maculatus, is a serious cosmopolitan pest of pulses. This beetle has lent itself as a guinea pig for several ecological studies. It harbors a consortium of bacterial communities in its gut, but the evidence for their role in its physiology is fragmentary. In this work, we hypothesized that gut microbiota mediates C. maculatus resistance to dichlorvos (DDVP or O,O-dimethyl O-2,2-dichlorovinylphosphate) and represent the target of Lippia adoensis (Gambian Tea Bush) essential oil (EO). Symbiotic and aposymbiotic beetles were exposed to artificial cowpea seeds earlier treated with DDVP or EO. Adult mortality and changes in gut bacterial community composition and abundance were examined at F₁ and F₅ generations. The susceptibility of experimental beetles to DDVP was significantly affected by their symbiotic status. The adult mortality decreased across generations in DDVP treatments, and remained significantly higher in aposymbiotic groups. In EO treatments, the mortality was consistent irrespective of symbiotic status and experimental generations. When compared to DDVP and the Control, EO treatments had significantly lower bacterial richness and diversity, as well as lower abundance of Proteobacteria, Firmicutes, and Bacteroidetes. These results support our hypothesis and describe the responses of gut microbial communities to pesticide treatments. This could be of interest for developing new management strategies of this pest.

Bactrocera minax is a major citrus pest distributed in China, Bhutan and India. The long pupal diapause duration of this fly is a major bottleneck for artificial rearing and underlying mechanisms remain unknown. Genetic information on B. minax transcriptome and gene expression profiles are needed to understand its pupal diapause. High-throughput RNA-seq technology was used to characterize the B. minax transcriptome and to identify differentially expressed genes during pupal diapause development. A total number of 52,519,948 reads were generated and assembled into 47,217 unigenes. 26,843 unigenes matched to proteins in the NCBI database using the BLAST search. Four digital gene expression (DGE) libraries were constructed for pupae at early diapause, late diapause, post-diapause and diapause terminated developmental status. 4,355 unigenes showing the differences expressed across four libraries revealed major shifts in cellular functions of cell proliferation, protein processing and export, metabolism and stress response in pupal diapause. When diapause was terminated by 20-hydroxyecdysone (20E), many genes involved in ribosome and metabolism were differentially expressed which may mediate diapause transition. The gene sets involved in protein and energy metabolisms varied throughout early-, late- and post-diapause. A total of 15 genes were selected to verify the DGE results through quantitative real-time PCR (qRT-PCR); qRT-PCR expression levels strongly correlated with the DGE data. The results provided the extensive sequence resources available for B. minax and increased our knowledge on its pupal diapause development and they shed new light on the possible mechanisms involved in pupal diapause in this species.