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Gene Transfer AgentsBacteria can experience genetic exchange (sex) through the process of transduction, where DNA is transferred between cells via infectious bacteriophages. But transduction seems rare in natural populations of bacteria, because it is an inadvertent mistake of ordinary phage infection. In contrast, the gene transfer agent (GTA) of Rhodobacter capsulatus is a phage-like element that resides in the bacterial chromosome, and packages and shuttles random pieces of genomic DNA between cells. Because GTA particles appear unable to induce normal phage infection, it has been proposed that GTA is a defective phage co-opted by R. capsulatus to promote gene exchange. Our current work examines the prevalence and expression of GTA-like elements in the alpha-proteobacteria, especially in the aquatic bacterium Caulobacter crescentus. We use comparative genomics to identify candidate GTA elements in sequenced bacterial genomes, and employ molecular genetics to verify the activity of these GTA-like elements. |