Unseen microbes influence the health and well-being of larger organisms, from humans to plants to insects. Some of these microbes cause disease, some are harmless, some are beneficial, and sometimes their effect depends on other microbes that are present in the same host organism. These microbial communities, or “microbiomesâ€, that share the same host can be very complicated, making it difficult to understand how different microbes affect each other and the host. However, arthropods such as insects and spiders often have simpler microbial communities that can serve as useful models for understanding microbial interactions and their combined effects on the host. Additionally, these simple microbial communities are often heritable, passed directly from arthropod mother to offspring, and can have major effects on their host’s biology and reproduction. In this project, the researchers will use a spider model system to investigate the consequences of microbe interactions. The agricultural spider, Mermessus fradeorum, can host a community of up to 5 strains of inherited bacteria. These bacteria manipulate the spider’s reproduction in complex ways that depend on which combination of bacterial strains are present. The expected research results will be particularly important for current and future efforts to use specific arthropod-hosted bacteria to manipulate and control arthropods that can transmit diseases. Undergraduate students, with an emphasis on the inclusion of underrepresented groups, will be trained through classroom activities, individual research experiments, and summer research internships. Outreach to the public will include spider-oriented events at schools and public events, including development of spider-oriented discovery cart series series at the University of Kentucky Arboretum.
The researchers will determine how the presence or absence of different bacteria affect: 1) the quantity and location of other members of the bacterial community within the host’s body, 2) the resulting reproductive biology of the spider, and 3) the spread of different bacterial community types in the spider population. The researchers will then use mathematical models to make more general predictions about how co-hosted bacteria cooperate versus compete within their shared host. The researchers will use antibiotics to differentially cure spiders of various strains of bacterial symbiont, then compare localization and quantity of other bacterial community members using fluorescent in situ hybridization (FISH) microscopy and quantitative PCR. The reproductive phenotype of differentially infected spiders will be evaluated via controlled matings to assess reproductive compatibility among different infection types and offspring sex ratio. Spiders with different symbiont communities will then be assembled into replicated laboratory populations that will be allowed to evolve over several generations, to assess the effects of the within-host microbial community on interactions among hosts with different microbial symbionts, and also to whether host population structure feeds back to affect the composition of the within-host symbiont community. Analytical and simulation models will be used to tie within-host interactions of co-infecting bacteria to among-host dynamics of population infection, which will provide a generalized framework for understanding bacterial interactions in more complex systems. This proposal was co-reviewed and co-funded by the Divisions of Environmental Biology and Integrative Biology in the Directorate for Biological Sciences.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
