Molecular kinetics of reviving bacterial spores

Bacterial spores can remain dormant for years, yet they possess a remarkable potential to rapidly resume a vegetative life form. Here, we identified a distinct phase at the onset of spore outgrowth, designated the ripening period. This transition phase is exploited by the germinating spore for molecular reorganization toward elongation and subsequent cell division. We have previously shown that spores of different ages, kept under various temperatures, harbor dissimilar molecular reservoirs (E. Segev, Y. Smith, and S. Ben-Yehuda, Cell 148:139-149, 2012). Utilizing this phenomenon, we observed that the length of the ripening period can vary according to the spore molecular content. Importantly, the duration of the ripening period was found to correlate with the initial spore rRNA content and the kinetics of rRNA accumulation upon exiting dormancy. Further, the synthesis of the ribosomal protein RplA and the degradation of the spore-specific protein SspA also correlated with the duration of the ripening period. Our data suggest that the spore molecular cargo determines the extent of the ripening period, a potentially crucial phase for a germinating spore in obtaining limited resources during revival.