Population Genetics and Genome Evolution of Viruses in an Aquatic Environment (2009 – Present)

Investigator:  Marcia Marston, Roger Williams University
Mentor: David Rand, Brown University 

Abstract:  Bacteriophages are important conduits for horizontal gene exchange among bacteria and are directly 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 through 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 population genetics and genome evolution of bacteriophages.  We will test the hypothesis that much of the genetic diversity within bacteriophage populations and communities can be attributed to recent horizontal genetic exchange events among phages and between phages and bacteria. 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 within populations and communities of natural aquatic bacteriophages. The specific aims of this research are to:  (1) Assess the frequency of horizontal gene transfer events and its influences on bacteriophage genome organization and evolution, (2) Examine the population genetics/genomics of specific bacteriophages to determine the extent to which bacteriophages in the same population carry different alleles of laterally transferred host-derived genes, (3) Analyze the composition and distribution of non-viral, non-host genetic material carried in bacteriophage genomes, and (4) Train undergraduate students both during the summer and the academic year in the key molecular genetic techniques used in biomedical research.  Students will gain experience in scientific communication, laboratory techniques, use of instrumentation, and bioinformatics as they complete individual projects.