Competitive Fitness During Feast and Famine: How SOS DNA Polymerases Influence Physiology and Evolution inEscherichia coli
Year: 2013
Type: article
Abstract: Escherichia coli DNA polymerases (Pol) II, IV, and V serve dual roles by facilitating efficient translesion DNA synthesis while simultaneously introducing genetic variation that can promote adaptive evolution. Here we show that these alternative polymerases are induced as cells transition from exponential to long-term stationary-phase growth in the absence of induction of the SOS regulon by external agents that damage DNA. By monitoring the relative fitness of isogenic mutant strains expressing only one alternative polymerase over time, spanning hours to weeks, we establish distinct growth phase-dependent hierarchies of polymerase mutant strain competitiveness. Pol II confers a significant physiological advantage by facilitating efficient replication and creating genetic diversity during periods of rapid growth. Pol IV and Pol V make the largest contributions to evolutionary fitness during long-term stationary phase. Consistent with their roles providing both a physiological and an adaptive advantage during stationary phase, the expression patterns of all three SOS polymerases change during the transition from log phase to long-term stationary phase. Compared to the alternative polymerases, Pol III transcription dominates during mid-exponential phase; however, its abundance decreases to <20% during long-term stationary phase. Pol IV transcription dominates as cells transition out of exponential phase into stationary phase and a burst of Pol V transcription is observed as cells transition from death phase to long-term stationary phase. These changes in alternative DNA polymerase transcription occur in the absence of SOS induction by exogenous agents and indicate that cell populations require appropriate expression of all three alternative DNA polymerases during exponential, stationary, and long-term stationary phases to attain optimal fitness and undergo adaptive evolution.
Source: Genetics
Institution: University of Southern California
Language: English
Subfield: Genetics
Domain: Life Sciences
Open Access status: bronze
Awards: CAREER: DNA as a Nutrient-A Role for Competence Gene Homologs in Long-Term Survival, Training in Cellular, Biochemical and Molecular Sciences, G426633967, ERROR CORRECTION IN DNA SYNTHESIS--A BIOCHEMICAL STUDY, G6671297155, Error Correction in DNA Synthesis: A Biochemical Study, Biochemical Basis of SOS-Induced Mutagenesis, G9000225134
OpenAlex ID: W2158061773