Name: Marcia Marston

Email: mmarston@rwu.edu

Author: Marcia F. Marston, Chris G. Amrich

Author affiliation: Roger Williams University, Bristol, Rhode Island USA

Abstract title: Genetic Exchange in a Coastal Cyanophage Population

Absstract:

Horizontal gene transfer and recombination are important evolutionary processes in viral evolution. Cyanophage genome evolution has been shaped both by non-homologous recombination events, which has led to differences in genome size and gene content, and by homologous recombination of gene segments among phages and between phages and their hosts. In this study we examined the role of genetic exchange in the divergence of cyanomyophage isolates belonging to the same population. Four core-viral genes (g20, portal protein; g43, DNA polymerase; g23, major capsid protein; and g101, putative tail fiber protein) and four viral-encoded bacterial-derived genes (psbA, photosystem II D1 protein; psbD, photosystem II D2 protein; cobS, a putative porphyrin biosynthetic protein; and phoH, a phosphate-starvation inducible protein) were analyzed from over 100 cyanophage isolates. The cyanomyophages included in this study were isolated from Rhode Island coastal waters on Synechococcus hosts. Phylogenetic analysis of concatenated sequences revealed well-resolved sequence clusters with an average nucleotide identity of 99.3 - 100%, which we have designated as strains. Extensive microdiversity was observed within each strain. This microdiversity was generated by point mutations, intragenic recombination between strains, and homologous recombination within a strain. Intragenic recombination events between distinct strains were detected most often in psbA genes, but were also identified in psbD and g23 genes. We are continuing to investigate how genetic exchange within a population influences the dynamics of viral-host interactions.