When disaster strikes: Reconstitution of population density by expansion of survivors.

Microorganisms have an assortment of stress-response mechanisms that enable them to survive in the face of environmental stresses. However, with prolonged exposures to severe stresses adaptive stress responses ultimately fail, the affected populations may suffer a massive decline. Recovery of the population density in the aftermath of a massive death is a vital task. Our recent post-stress regrowth under starvation (RUS) studies prompted us to propose RUS as an adaptation for overcoming consequences of devastating environmental disturbances. RUS should be seen as an integral process having two major aspects: the stress-induced cellular auto-decomposition and the recycling of the released nutrients. Here, we summarized what is already known about RUS and suggest a number of questions that are key to understanding the molecular underpinnings of these two operations. We also interrogate the prospect that would conceptualize the auto-decomposition as a fitness-maximizing mechanism acting with the purpose of an expedient supply of nutrients. Two further things are of special note: given that some of the RUS-defective mutants are also impaired in DNA repair, RUS can serve as an important tool for uncovering new determinants operating, in some overlapping fashion, in the protection of genome integrity; also, RUS can serve as a new angle of approach that might, hopefully, assign roles to some of those (up to ~ 30%) of microbial genes that are of unknown function. More generally, understanding post-stress reconstitution and the underlying mechanisms is a necessary (complementing) part of any comprehensive picture of how microbes cope with very harsh environmental disturbances.