Gut bacterial population and community dynamics following adult emergence in pest tephritid fruit flies

Authors: Mason, Charles; Auth, Jean; Geib, Scott

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2023
Publication Date: 8/22/2023
Citation: Mason, C.J., Auth, J.E., Geib, S.M. 2023. Gut bacterial population and community dynamics following adult emergence in pest tephritid fruit flies. Scientific Reports. 13. Article 13723. https://doi.org/10.1038/s41598-023-40562-2.
DOI: https://doi.org/10.1038/s41598-023-40562-2

Interpretive Summary: Tephritid fruit flies (Diptera: Tephritidae) form robust relationships with a diverse set of microorganisms in their digestive tract. These microorganisms can influence insect physiology and influence the hosts' behaviors. In this study, we evaluated the dynamics of the bacterial components in the gut following adult emergence from pupae by assessing bacterial communities of melon fly (Zeugodacus cucurbitae) and medfly (Ceratitis capitata). Flies were sampled days and weeks following adult emergence, and their guts were dissected to enumerate bacteria and extract DNA. We determined the abundances of bacteria decreased following adult emergence from pupae, but recovered withing 24h. Additionally, for both fly species there were considerable shifts in gut microbiome composition, indicating a high degree of pliability upon entering adult stages. These data have important implications towards informing host-microbe interactions in invasive fruit flies, as well as help inform how microorganisms can be exploited for improving flies for sterile insect technique (SIT).

Technical Abstract: Insects form pivotal relationships with gut microorganisms, where their presence can facilitate multiple aspects of host physiological ecology. These relationships are dynamic and can change as hosts age and/or encounter different environments. A turning point in insect-microbe interactions involves the metamorphosis into the adult lifestages, especially for holometabolous insects. Improved knowledge of population and community dynamics of gut microbiomes upon adults emergence inform drivers of community assembly and physiological aspects of host-microbe interactions. Here, we evaluated the bacterial communities of the tephritid fruit flies melon fly (Zeugodacus cucurbitae) and medfly (Ceratitis capitata) associated with pupae and timepoints immediately following adult eclosion. We used a combination of culturing to determine cultivatable bacterial titers, qPCR to determine 16S-rRNA SSU copy numbers, and 16S V4 sequencing to determine changes in communities. Both culturing and qPCR revealed that fly bacterial populations declined upon adult emergence by 10-100× followed by recovery within 24h following eclosion. Titers reached ~107 CFUs (~108 16S rRNA copies) within a week post emergence. We also observed concurrent changes in amplicon sequence variance (ASVs), where the ASV composition differed overtime for both melon fly and medfly adults at different timepoints. Medfly, in particular, had different microbiome compositions at each timepoint, suggesting longer periods of flux before stabilizing. These results demonstrate that tephritid microbiomes experience a period of flux following adult emergence, where both biomass and the makeup of the community undergoes dramatic shifts. These dynamics suggest that there maybe a period where the tephritid gut microbiome may be pliable to introduce and establish new strains in the host.