Marine microorganisms are abundant and diverse. What drives this diversity? Mutation and natural selection appear to account for only a portion of it. The ability to sequence genomes is demonstrating that lateral gene transfer (LGT), the indiscriminant movement of genes between unrelated microbes, plays a significant role in generating diversity, and it is now recognized as a major driving force in microbial evolution. In this project, Paul and McDaniel of the University of South Florida argue that the three known mechanisms of prokaryotic gene transfer (transduction, transformation, and conjugation) appear to be unable and unlikely to occur with sufficient frequency in the marine environment to be significant drivers of microbial diversity. In order to examine other factors contributing to microbial diversity, these investigators will be evaluating the significance of a novel form of LGT which involves little-understood particles called Gene Transfer Agents (GTAs). GTAs are phage-like particles encoded in the genomes of particular groups of bacteria (alpha-proteobacteria) that package random fragments of host genomic DNA. These particles do not lyse their host, but rather inject their prior host's DNA into a new host, and the transferred DNA then integrates into the new host's genome. Genomic sequencing has recently revealed the prevalence of GTAs in alpha-proteobacterial genomes, and a survey of 102 marine bacterial genomes indicated twenty (20%) contained putative GTAs. The abundance of GTAs in the Roseobacter lineage, an alpha-proteobacteria group that can comprise up to 25% of the bacteria in coastal environments, may make GTAs the most important mechanism of LGT in the marine environment. These researchers want to know: if GTAs are abundant in bacterial genomes, what are they doing? These investigators will be examining the gene transfer capability of marine GTAs by using known hosts and known genetic tracers, like plasmids. They will also determine the occurrence of GTA-containing bacteria in marine coastal populations by using marker genes diagnostic for specific GTAs. Finally, the investigators will evaluate the potential for GTAs to transfer genes within indigenous populations of marine bacteria. In these experiments, these investigators will track the movement of DNA between lab strains and indigenous bacteria and then between populations of indigenous bacteria to estimate the natural rate of gene transfer by GTAs in the ocean. The longterm goal of this research by Paul and McDaniel is to elucidate the role of a little understood form of LGT in the marine environment, setting the stage for follow on studies on the flux of genes via GTAs and on what controls microbial diversity in the oceans. The PIs will carry out a number of outreach activities as a part of this project. They will be developing high school lab modules on GTA indicators and will be using them in classes from ethnically and racially diverse schools in Pinellas County, FL. They will continue their participation in the Oceanography Camp for Girls, a three week day camp each summer, hosted by the USF College of Marine Science, for students entering the 9th grade. THe PIs plan to add a GTAs detector component to these lab activities.
