Upon starvation, the bacterium Bacillus subtilis enters the process of sporulation, lasting several hours and culminating in formation of a spore, the most resilient cell type known. We show that a few days following sporulation, the RNA profile of spores is highly dynamic. In aging spores incubated at high temperatures, RNA content is globally decreased by degradation over several days. This degradation might be a strategy utilized by the spore to facilitate its dormancy. However, spores kept at low temperature exhibit a different RNA profile with evidence supporting transcription. Further, we demonstrate that germination is affected by spore age, incubation temperature, and RNA state, implying that spores can acquire dissimilar characteristics at a time they are considered dormant. We propose that, in contrast to current thinking, entering dormancy lasts a few days, during which spores are affected by the environment and undergo corresponding molecular changes influencing their emergence from quiescence.
Bibliographical noteFunding Information:
We thank M. Kott-Gutkowski (Hebrew University, Israel), A. Sol (Hebrew University), B. Fhanetzky (Tamar, Ltd.), and A. Grundwag (Eisenberg bros., Ltd.) for valuable technical support. We are grateful to A. Rosenberg and other members of the Ben-Yehuda laboratory for technical help and valuable discussions and comments. We thank G. Bachrach (Hebrew University), R. Losick (Harvard University, USA), A. Rouvinski (Hebrew University), I. Simon (Hebrew University), and J. Stülke (Göttingen University, Germany) for valuable comments on the manuscript. We thank the National BioResource Project National Institute of Genetics, Japan (NBRP [NIG, Japan]), D. Bechhofer (Mt. Sinai School of Medicine, USA), C. Condon (CNRS, France), J. Errington (Newcastle University, UK), H. Putzer (CNRS), and J. Stülke (Göttingen University) for kindly providing strains. This work was supported by the European Research Council (ERC) Starting Grant (209130) and by the Israel Science Foundation (696/07) awarded to S.B.-Y.