This project investigates the coevolutionary arms race between viruses and their microbial hosts in two, geographically isolated, geothermal hot springs populations. Microorganisms swap genes on mobile elements such as viruses. It has recently been discovered that bacteria and archaea maintain an acquired, heritable immune system that allows them to fight off viral infections. This and other forms of microbial resistance can prevent infection and therefore limit the transfer of genes on viruses. In response to host resistance, viruses evolve rapidly to evade host immunity. This project will use comparative full genomic analysis of viruses and their archaeal hosts, Sulfolobus islandicus, combined with laboratory infection assays, to test for the genomic causes of infection or resistance among viruses and their hosts. The unique physical isolation of geothermal archaeal populations presents an ideal system in which to study whether the intimate local interaction between hosts and their viruses leads to specificity that restricts the movement of genes to endemic populations of microbes.
Microbial genomes harbor the vast majority of genetic diversity on earth, yet little is understood about how this diversity evolved. The movement of genes on viruses is critical to microbial evolution, and can lead to the transfer of antibiotic resistance and other pathogenic factors. Specifically, how microbial immune resistance and viral evolution affects the flow of genes among microorganisms is unknown. Studying these interactions will increase understanding of microbial immunity and how it effects the evolution and diversity of both viruses and their microbial hosts. This project will include training two graduate students and three undergraduates in an interdisciplinary approach to biology which combines microbiology, virology, evolutionary ecology, and genomics. In addition, this project brings the exciting fields of microbial diversity and evolution to eleventh grade classrooms through a month-long laboratory module in experimental evolution, where students will witness, first-hand, microbial populations adapting to resist viral infection.
Viruses of microbes are believed to be key players in microbial ecosystems as the primary predators and as potent agents of gene transfer. By characterizing novel virus-host interaction in this model system both mediated by CRISPR/cas immunity and CRISPR independent we have expanded our understanding of the molecular mechanisms through which microbial viruses and their host interact. These novel mechanisms and patterns can be integrated into modeling of microbial evolution and ecology to better understand, predict, and manipulate the microbial communities on which every ecosystem on Earth depends. We have uncovered new diversity of viruses found in Kamchatka, Russia and Yellowstone National Park (See Figure 1) that infect organisms from the Domain Archaea. In doing so we are learning unifying concepts about how organisms interact with viral parasites across the three Domains of life. Two female graduate students were trained using the funds from the proposal. These students (one Latina) are moving into the highly skilled work force. Both will serve as role models for other women in science due to their success. In addition, six undergraduates were trained during the course of this grant. These students have gone on to graduate school and bring with them a sophisticated understanding of interdisciplinary research science. So far 40 high school teachers have been integrated into Project Microbe and are using this curriculum in their classrooms. This will develop scientific literacy in high school teachers and students and a better understanding of the natural microbial world that lives in us and around us all the time.
