Horizontal Gene Exchange and Genome Evolution of Viruses in an Aquatic Environment (2008 – Present)

Investigator:  Marcia Marston, Roger Williams University 

Abstract:  Bacteriophages are responsible for the virulence of many bacterial pathogens. Phage-encoded virulence factors include the shiga toxins in pathogenic strains of Escherichia coli, the cholera toxin in Vibrio cholerae, and the botulinum neurotoxins in Clostridium botulinum. Bacteriophages can drive the emergence and evolution of new pathogenic bacterial strains by the horizontal transfer of virulence factors and thus an understanding of phage genome evolution has important public health implications. This research project will examine the genetic structure, dynamics, and evolution of phage genomes. We will test the hypothesis that much of the current phage diversity can be attributed to recent horizontal genetic exchange events among phages and their hosts. A natural community of aquatic bacteriophages belonging to the Myoviridae and Podoviridae families will be used as a model system to address questions about phage genome evolution and the frequency of horizontal gene transfer. PCR primers for core-viral genes as well as host-derived genes will be designed. Viral and host-derived genes will be sequenced from bacteriophages isolated over the past ten years as well as from new isolates obtained from Narragansett Bay. Bioinformatic tools will be used to analyze these sequences to: (1) construct phylogenetic gene and genome trees, (2) compare relative rates of divergence among genes, (3) detect and date horizontal gene transfer events, and (4) assess the number of possible genetic exchanges among phages and between phages and their hosts. Undergraduate students will participate in all aspects of the research. This pilot project will train undergraduate students both during the summer and the academic year in key molecular genetic techniques used in biomedical research. Students will gain experience in scientific communication, laboratory techniques, use of key instrumentation, and bioinformatics as they complete individual projects.