Stochastic and Heritable Responses in Cell-Size Regulation and Survival to pH Stress in C. glutamicum

Abstract

Bacterial survival in fluctuating environments depends on the ability of individual cells to maintain physiological homeostasis under stress, yet how single cells recover from transient pH fluctuations remains poorly understood. We tracked the cell-size dynamics and survival of Corynebacterium glutamicum cells exposed to short, strong acid (pH 4, 20 min) or alkaline (pH 11, 15 min) pulses. Acid stress considerably increases the size added during the stress cycle, whereas alkaline stress increases it only modestly. Nevertheless, surviving cells maintain their division strategy and restore size homeostasis in the next cycle. Coordination between relatives is short-lived: sister cells have similar cell-cycle durations after stress, but durations become uncorrelated once the last division shared by two cells precedes the stress by more than about 1.5 generations. Survival of acid stress favors larger cells and is largely stochastic, with no detectable lineage heritability. In contrast, survival of alkaline stress favors smaller cells and is transiently heritable: co-survival probability remains high among relatives separated by up to two generations. These findings provide insight into pH survival in C. glutamicum and present statistical methods to study cell-size regulation and survival under transient, severe environmental fluctuations.