Single-Cell Analysis of the Dps Response to Oxidative Stress

Microorganisms have developed an elaborate spectrum of mechanisms to respond and adapt to environmental stress conditions. Among these is the expression of dps, coding for the DNA-binding protein from starved cells. Dps becomes the dominant nucleoid-organizing protein in stationary-phase Escherichia coli cells and is required for robust survival under stress conditions, including carbon or nitrogen starvation, oxidative stress, metal exposure, and irradiation. To study the complex regulation of Dps in E. coli, we utilized time-lapse fluorescence microscopy imaging to examine the kinetics, input encoding, and variability of the Dps response in single cells. In the presence of an oxidative stressor, we observed a single pulse of activation of Dps production. Increased concentrations of H₂O₂ led to increased intensity and duration of the pulse. While lower concentrations of H₂O₂ robustly activated the Dps response with little effect on the growth rate, higher concentrations of H₂O₂ resulted in dramatically lower and highly varied growth rates. A comparison of cells exposed to the same concentration of H₂O₂ revealed that increased levels of Dps expression did not confer a growth advantage, indicating that recovery from stress may rely primarily upon variation in the amount of damage caused to individual cells.

IMPORTANCE

We show for the first time the response of the DNA-binding protein from starved cells ( Dps) to oxidative stress in single cells of E. coli. Through time-lapse fluorescence microscopy, a single pulse of Dps production is observed in cells exposed to H₂O₂, with a duration and intensity of induction proportional to the concentration of the applied stress. More intense Dps expression did not provide a growth benefit to the bacteria, suggesting that healing from oxidative stress may largely depend upon the amount of damage in each individual cell.