The effect of diet and radiation on the bacterial symbiome of the melon fly, Zeugodacus cucurbitae (Coquillett)

Abstract

BackgroundSymbiotic bacteria contribute to a multitude of important biological functions such as nutrition and reproduction and affect multiple physiological factors like fitness and longevity in their insect hosts. The melon fly, Zeugodacus cucurbitae (Coquillett), is an important agricultural pest that affects a variety of cultivated plants belonging mostly to the Cucurbitaceae family. It is considered invasive and widespread in many parts of the world. Several approaches are currently being considered for the management of its populations including the environmentally friendly and effective sterile insect technique (SIT), as a component of an integrated pest management (IPM) strategy. In the present study, we examined the effect of diet and radiation on the bacterial symbiome of Z. cucurbitae flies with the use of Next Generation Sequencing technologies.ResultsMelon flies were reared on two diets at the larval stage, an artificial bran-based diet and on sweet gourd, which affected significantly the development of the bacterial profiles. Significant differentiation was also observed based on gender. The effect of radiation was mostly diet dependent, with irradiated melon flies reared on the bran diet exhibiting a significant reduction in species diversity and richness compared to their non-irradiated controls. Changes in the bacterial symbiome of the irradiated melon flies included a drastic reduction in the number of sequences affiliated with members of Citrobacter, Raoultella, and Enterobacteriaceae. At the same time, an increase was observed for members of Enterobacter, Providencia and Morganella. Interestingly, the irradiated male melon flies reared on sweet gourd showed a clear differentiation compared to their non-irradiated controls, namely a significant reduction in species richness and minor differences in the relative abundance for members of Enterobacter and Providencia.ConclusionsThe two diets in conjunction with the irradiation affected significantly the formation of the bacterial symbiome. Melon flies reared on the bran-based artificial diet displayed significant changes in the bacterial symbiome upon irradiation, in all aspects, including species richness, diversity and composition. When reared on sweet gourd, significant changes occurred to male samples due to radiation, only in terms of species richness.

New Insights on the Zeugodacus cucurbitae (Coquillett) Bacteriome

“…This could lead to the loss of important bacteria for the physiology of the mass-reared flies and a subsequent loss of fitness. Sex related differences in the microbiota have been documented in both wild and laboratory populations of the fly [ 10 , 13 ]. In this work however, only male subjects were analyzed, due to the fact that samples were collected using traps with male attractants.…”

“…Bacterial strains isolated from stable microbial communities of wild individuals can be provided to mass-reared insects as supplements, in an attempt to replicate the natural microbiome and improve fitness and mating success [ 5 , 6 , 7 ]. Studies dealing with tephritid microbiomics use either samples from laboratory colonies [ 8 , 9 , 10 , 11 , 12 , 13 ] or wild populations [ 10 , 14 , 15 , 16 , 17 , 18 ], which are generally characterized by higher microbial diversity compared to laboratory strains [ 10 , 19 ]. Therefore, it is important to identify and exploit this large portion of diversity, but also to determine how it is affected by the geographical isolation of wild populations.…”

Comparative Microbiomics of Tephritid Frugivorous Pests (Diptera: Tephritidae) From the Field: A Tale of High Variability Across and Within Species

“…Most of the currently available research on tephritid gut microbiomics focuses on fruit fly laboratory populations (i.e., fed with artificial diets) and often aims at investigating the optimal rearing conditions for species of interest for the sterile insect technique (SIT) ( Augustinos et al, 2015 , 2019 ; Kyritsis et al, 2017 , 2019 ; Asimakis et al, 2019 ) while the composition and levels of variability of microbiome profiles of wild tephritid flies are far less known.…”

Role of Commensal Microbes in the γ-Ray Irradiation-Induced Physiological Changes in Drosophila melanogaster

“…Radiation alters the gut microbiome, which is considered an important biomarker of host health [ 72 ]. Interestingly, the abundance and composition of specific taxa were reported to change after radiation exposure [ 40 , 41 , 73 ]. For example, the diversity of the gut microbiota was decreased in the fecal sample of mice subjected to ionizing radiation compared with that of non-irradiated mice [ 40 ].…”

“…When melon flies were reared on an artificial bran-based diet, bacterial genera, such as Raoultella and Citrobacter , were reduced considerably, while sequences affiliated with members of Providencia , Morganella , and Enterobacter were increased. When flies were reared on sweet gourd, however, there was a significant decrease in species richness and minor differences in the relative abundance for members of Enterobacter and Providencia [ 73 ]. In the current study, the microbial floral change in D. melanogaster was analyzed after γ-ray irradiation at the third larval stage.…”