Virology; Molecular Biology; Biology of the Prokaryotes
I am investigating genes that may play a role in allowing the soil bacterium Acinetobacter baylyi strain ADP1 to survive under starvation conditions. Many bacteria spend most of their time in environments with limited nutrients and have evolved a variety of mechanisms for survival under such conditions. I am interested in identifying the genes involved in these mechanisms. To this end, my students and I used a genetic strategy to identify genes induced during stationary phase Acinetobacter. Stationary phase occurs when a culture of bacteria exhausts a required nutrient in its medium. The vast majority of cells in the population dies, but the survivors adapt to this nutrient deprivation. After screening more than 3500 isolates, we identified 123 clones that have a lacZ reporter cassette inserted into a chromosomal gene that is induced by stationary phase conditions. Inverse PCR with primers in the lacZ gene followed by DNA sequencing were used to locate the open reading frames containing the cassettes in these strains. Nearly three dozen strains that show very strong induction in stationary phase have the cassette in genes with high homology to the pilT and pilU genes of Pseudomonas. These genes, which have not previously been described in Acinetobacter, encode NTPases that are involved in twitching motility and in the uptake of DNA in natural transformation. The next most frequent location of the cassette insertion is in a homolog of the tolB gene, a periplasmic transport system component that is known to be upregulated by iron restriction during stationary phase in Pseudomonas. A gene homologous to the pyrophosphohydrolase mutT has also been identified in several strains. MutT prevents oxidative damage to DNA by degrading 8-oxodGTP before it becomes incorporated into DNA. We have begun knock-out studies to determine if these induced genes are required for survival during starvation. Among other genes that have also been identified are ones encoding arginyl- and glutamyl-tRNA synthetases, carbamoylphosphate synthetase, shikimate kinase, aldehyde dehydrogenase, EF-B, and possible serine/threonine kinases, multidrug resistance proteins, and penicillin-binding protein.