Conditional senescence in prokaryotes

Abstract

Bacteria are immortal in the sense that their capacity for reproduction appears limitless as long as the environment supports growth. However, this reproductive ability is gradually lost upon famine conditions. The loss of reproductive ability is one of the first signs of physiological deterioration and is followed by a collapse of the membrane integrity. The underlying molecular mechanism behind this degenerative change and decline is something of an enigma in bacteriology. Still, recent analysis of the conditional deterioration of growth arrested Escherichia coli cells has revealed interesting similarities with the aging process of higher organisms. The similarities include oxidation of proteins and its target specificity, the role of antioxidants and oxygen tension, and an apparent antagonism between reproduction and survival activities. The analysis of the E. coli model system has also revealed a novel culprit in the oxidation of proteins, i.e. an intimate link between the fidelity of the translational apparatus and oxidative modification of proteins. This review summarizes and evaluates the models of bacterial conditional deterioration and relates them to contemporary theories of aging in higher organisms.