Grant: Operating Grant

This proposal is to study how bacteria control the production of unusual virus-like particles (gene transfer agents, or GTAs) that have the sole function of transferring genes from a donor to a recipient cell. Our focus has been on the first-discovered and best-understood GTA of the environmental bacterium Rhodobacter capsulatus (R. capsulatus), to develop broadly applicable tools and knowledge. We found that less than 1% of a population of cells are activated to produce a GTA, and that these cells effectively commit suicide in the process of releasing GTA particles. We wish to determine exactly how this small subset of cells are activated to differentiate from the majority, and the biochemical pathways leading to the turn on/off of GTA genes. We have discovered a novel gene that, when mutated, increases the frequency of GTA production by more than 10,000-fold, leading to a great increase in the percentage of the cell population that dies. Although we discovered that many species of bacteria contain GTA-like genes, only a few are known to produce a GTA, mainly because this question has not been widely addressed. The pathogenic bacterium Brucella abortus contains a cluster of genes that are very similar to the R. capsulatus GTA gene cluster, and so we hypothesize the B. abortus also produces a GTA. I propose to hone our expertise and improve the understanding of the experimentally tractable R. capsulatus GTA, while using the tools that we develop to investigate the possibility of GTA production in B. abortus, and perhaps other pathogens in the longer term. Although this is fundamental research, our work has the potential to improve methodologies for treating bacterial infections by activating GTA-related pathways leading to death of the pathogen.