A phenotypic switch during starvation of Salmonella is coordinated by ribosomal transcription termination and degradation

Inside the host gut, enteric bacteria undergo cycles of growth and starvation, to which they must adapt swiftly. One important strategy for adjusting growth rates relies on ribosomal levels. While high ribosomal levels promote high growth rates, the dynamics and factors that underlie ribosomal degradation during starvation remain unclear. I will present a study in which we analyzed ribosomal levels of individual Salmonella Typhimurium cells using Fluorescence In-Situ Hybridization (rRNA-FISH). During the transition from exponential to stationary phase we measured a dramatic decrease of ribosomal levels only in a subpopulation, resulting in cells with high and low ribosomal content. We identified DksA and RNase I as regulators of ribosome transcription termination and degradation, respectively. Genetic pertubation of each provided the ability to resume growth faster in the transition from starvation to growth. Our results suggest that Salmonella employs a bet-hedging strategy in regulating ribosomal levels that may be beneficial for survival inside the host.