Biers, E. J., K. Wang, C. Pennington, R. Belas, F. Chen, and M. A. Moran. 2008. Occurrence and expression of Gene Transfer Agent (GTA) genes in marine bacterioplankton. Applied and Environmental Microbiology. In press.

Genes with homology to the transduction-like gene transfer agent (GTA) were observed in genome sequences of three cultured members of the marine Roseobacter clade. A broader search for homologs for this host-controlled viral-like gene transfer system identified likely GTA systems in cultured Alphaproteobacteria, and particularly in marine bacterioplankton representatives. Expression of GTA genes and extracellular release of GTA particles (~50-70 nm) was demonstrated experimentally for Roseobacter clade member Silicibacter pomeroyi DSS-3, and intra-specific gene transfer was documented. GTA homologs are surprisingly infrequent in marine metagenomic sequence data, however, and the role of this lateral gene transfer mechanism in ocean bacterioplankton communities remains unclear.