Gene transfer agents: phage-like elements of genetic exchange

Top Cited Papers
Publisher Website
Google Scholar
Abstract
Gene transfer agents (GTAs) are phage-like entities that contain a random piece of the genome of the producing cell. The amount of DNA that a GTA contains is insufficient to encode the protein components of the particle itself. Instead, structural GTA genes are encoded within the genome of the producing cell. All known GTAs have tailed-phage structures, which presumably are released into the environment by lysis of the producing cell. Released GTA particles can transfer DNA from the producing cell to a recipient cell. GTAs are thought to bind to recipient cells through specific tail–receptor interactions, but no receptors have been identified to date. Four genetically unrelated GTAs have been identified to date: RcGTA in the alphaproteobacterium Rhodobacter capsulatus, Dd1 in the deltaproteobacterium Desulfovibrio desulfuricans, VSH-1 (virus of Serpulina hyodysenteriae) in the spirochaete Brachyspira hyodysenteriae and VTA (voltae transfer agent) in the archaeon Methanococcus voltae. Two of these entities, RcGTA and Dd1, have been characterized in detail, and there are some details available for VSH-1 and VTA. The known GTAs show structural similarity to siphoviruses or podoviruses. There are several possible evolutionary scenarios that would explain the connections between GTAs and phages, as well as some evidence suggesting that the four known GTAs evolved independently. There are various potential functions for GTA-mediated gene transfer. One suggestion is that GTAs are public goods which provide a means of altruistic cooperation between related microorganisms.