Influence of inoculated gut bacteria on the development of Bactrocera dorsalis and on its susceptibility to the entomopathogenic fungus, Metarhizium anisopliae

Abstract

Background: Symbiotic interactions between insects and bacteria have been associated with a vast variety of physiological, ecological and evolutionary consequences for the host. A wide range of bacterial communities have been found in association with the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), an important pest of cultivated fruit in most regions of the world. We evaluated the diversity of gut bacteria in B. dorsalis specimens from several populations in Kenya and investigated the roles of individual bacterial isolates in the development of axenic (germ-free) B. dorsalis fly lines and their responses to the entomopathogenic fungus, Metarhizium anisopliae. Results: We sequenced 16S rRNA to evaluate microbiomes and coupled this with bacterial culturing. Bacterial isolates were mono-associated with axenic B. dorsalis embryos. The shortest embryonic development period was recorded in flies with an intact gut microbiome while the longest period was recorded in axenic fly lines. Similarly, larval development was shortest in flies with an intact gut microbiome, in addition to flies inoculated with Providencia alcalifaciens. Adult B. dorsalis flies emerging from embryos that had been mono-associated with a strain of Lactococcus lactis had decreased survival when challenged with a standard dosage of M. anisopliae ICIPE69 conidia. However, there were no differences in survival between the germ-free lines and flies with an intact microbiome. Conclusions: These findings will contribute to the selection of probiotics used in artificial diets for B. dorsalis rearing and the development of improved integrated pest management strategies based on entomopathogenic fungi.

Multitrophic effects: A tale of microbiome shifts in the oriental fruit fly, Bactrocera dorsalis and its parasitoids

“…Similar to earlier microbiome reports from tephritids [10,17,27, 28], we found that, Proteobacteria and Firmicutes were the most abundant bacterial phyla in B. dorsalis larvae. This nding suggests the intimate association between B. dorsalis and these phyla, and that they could be contributing to the physiological functioning of this pest such as development and nutrient digestion among others.…”

“…This nding suggests the intimate association between B. dorsalis and these phyla, and that they could be contributing to the physiological functioning of this pest such as development and nutrient digestion among others. Earlier studies [16,17,19,21,29] investigating Proteobacteria and Firmicutes bacterial strains and their roles in the eco-physiological functions of B. dorsalis con rm this phenomenon.…”

“…Dissection of B. dorsalis, D. longicaudata and P. cosyrae guts Forty-eight hours after exposure to the parasitoids, B. dorsalis larvae were dissected under a stereomicroscope (Zeiss Stemi 508, Zeiss, Oberkochen, Germany), to ascertain parasitism (presence of a parasitoid larva and/or egg). Once parasitism was con rmed, the guts of the larvae were extracted as described [17]. Brie y, the larvae were surface sterilized in 2% sodium hypochlorite solution, 70% ethanol and in distilled water, sequentially.…”

“…Among these microbes are bacteria belonging to Lactococcus, Klebsiella, and Providencia genera. These microbes in uence oviposition behaviour, development, immunity, nutritional pro les, foraging behavior [16][17][18][19][20] and defense against parasitoids in this pest [21].…”