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In macroscopic organisms, aging is often obvious; in single-celled organisms, where there is the greatest potential to identify the molecular mechanisms involved, identifying and quantifying aging is harder. The primary results in this area have come from organisms that share the traits of a visibly asymmetric division and an identifiable juvenile phase. As(More)
Because most newly arising mutations are neutral or deleterious, it has been argued that the mutation rate has evolved to be as low as possible, limited only by the cost of error-avoidance and error-correction mechanisms. But up to one per cent of natural bacterial isolates are 'mutator' clones that have high mutation rates. We consider here whether high(More)
Mutation and subsequent recombination events create genetic diversity, which is subjected to natural selection. Bacterial mismatch repair (MMR) deficient mutants, exhibiting high mutation and homologous recombination rates, are frequently found in natural populations. Therefore, we have explored the possibility that MMR deficiency emerging in nature has(More)
BACKGROUND Microbes engage in a remarkable array of cooperative behaviors, secreting shared proteins that are essential for foraging, shelter, microbial warfare, and virulence. These proteins are costly, rendering populations of cooperators vulnerable to exploitation by nonproducing cheaters arising by gene loss or migration. In such conditions, how can(More)
We have shown that bacterial mutation rates change during the experimental colonization of the mouse gut. A high mutation rate was initially beneficial because it allowed faster adaptation, but this benefit disappeared once adaptation was achieved. Mutator bacteria accumulated mutations that, although neutral in the mouse gut, are often deleterious in(More)
Life history theory accounts for variations in many traits involved in the reproduction and survival of living organisms, by determining the constraints leading to trade-offs among these different traits. The main life history traits of phages-viruses that infect bacteria-are the multiplication rate in the host, the survivorship of virions in the external(More)
The evolutionary significance of stress-induced mutagenesis was evaluated by studying mutagenesis in aging colonies (MAC) of Escherichia coli natural isolates. A large fraction of isolates exhibited a strong MAC, and the high MAC variability reflected the diversity of selective pressures in ecological niches. MAC depends on starvation, oxygen, and RpoS and(More)
The quantitative study of the cell growth has led to many fundamental insights in our understanding of a wide range of subjects, from the cell cycle to senescence. Of particular importance is the growth rate, whose constancy represents a physiological steady state of an organism. Recent studies, however, suggest that the rate of elongation during(More)
Oxidized guanine (8-oxo-7,8-dihydroguanine; 8-oxo-G) is a potent mutagen because of its ambiguous pairing with cytosine and adenine. The Escherichia coli MutT protein specifically hydrolyzes both 8-oxo-deoxyguanosine triphosphate (8-oxo-dGTP) and 8-oxo-guanosine triphosphate (8-oxo-rGTP), which are otherwise incorporated in DNA and RNA opposite template A.(More)