TO BE OR NOT TO BE - THE ULTIMATE DECISION OF THE GROWTH-ARRESTED BACTERIAL-CELL

The evolutionary survival of prokaryotes has depended not only on thei r performance during conditions that allow rapid growth, but also on t heir ability to adjust their internal affairs to enhance survival duri ng prolonged periods of growth arrest. The small size of prokaryotes l imits their ability to control their environment, and instead, their a bility to cope with environmental challenges must rely on rapid and ef ficient control of gene expression. The majority of genes responding t o a specific environmental condition causing growth arrest are, in gen eral, uniquely induced by one specific stimulus. However, many genes, operons and regulons do not exclusively respond to one particular stre ss condition, and some regulons appear to be related in the sense that they share member genes. Furthermore, growth-arrest conditions activa te several seemingly unlinked regulatory networks and several genes/pr oteins seem to respond to growth arrest in general. These proteins are interesting because we know very little about why growth-arrested, st ationary phase cells ultimately die, and functional analysis of such g eneral responders to growth arrest may help us to understand the genet ic/biochemical basis for the bacterial defence against ageing processe s. In this paper I review recent findings suggesting that several gene ral responders to stasis form an integral part of a defence system aim ed at avoiding the damaging effects of endogenously generated oxygen r adicals. In addition, the curious finding that some proteins of a regu lon are involved in enhancing the life-span of the growth-arrested cel l while other members of the same regulon are devoted to killing it wi ll be discussed. (C) 1998 Federation of European Microbiological Socie ties. Published by Elsevier Science B.V.