CAREER: DNA as a Nutrient-A Role for Competence Gene Homologs in Long-Term Survival

University Of Southern California, Los Angeles CA

Investigators

Abstract

Most models of the natural history of bacteria include cycles of "feast and famine," where the organism experiences nutrient abundance as well as nutrient stress. However, for most microorganisms, nutrient availability is usually restricted. To understand mechanisms of bacterial survival under laboratory conditions that better reflect the natural environment, we study the nutrient-limited stationary phase of the E. coli life cycle. We have identified a gene family essential for E. coli to survive long-term incubation during stationary phase. The activities of these genes enable the bacteria to use extracellular DNA as the sole source of carbon and energy. These genes are homologs of genes in other organisms known to be involved in horizontal gene transfer, making the cells competent for natural transformation. Therefore, they are known as "com" genes. However, unlike bacteria such as Haemophilus influenzae or Bacillus subtilis that are naturally competent for genetic transformation, E. coli is not known to be naturally transformable. The identification of these genes in E. coli suggests that the organism takes up DNA not necessarily to be used as genetic information, but also to be used as a carbon and energy source. The focus of this project is to understand the ability of E. coli to use DNA as a nutrient, determine the roles of these com genes in DNA catabolism, and elucidate the patterns of com gene expression and regulation. This project also includes the introduction of a new course, "Mechanisms of Bacterial Survival, Adaptation & Evolution", whose focus is to explore the mechanisms used by a variety of microorganisms to survive in disparate environments, allowing them to adapt to environmental change.