ABSTRACT
This chapter focuses on evidence for environmentally influenced mutation in microorganisms, specifically mutation promoted by stress or starvation. This is called stressful lifestyle-associated mutation, or SLAM. The classic experiments of Luria and Delbruck, Newcombe, and the Lederbergs demonstrated that some mutations in bacteria form independently of their selective value, and apparently randomly, in growing cells. Stationary-phase Lac- mutation occurs by a molecular mechanism different from growth-dependent mutation. They found that an altered-fiinction allele of the gene encoding the recombination protein RecA diminished late, but not early-arising Lac-colonies, arguing for RecA-dependence of the stationary-phase, but not growth-dependent mutation process. Because RecBCD gains access to DNA only at double-strand ends, double-strand breaks are implicated as a molecular intermediate in recombination-dependent SLAM. The chapter discusses examples in bacteria of mutations that are associated with, and may be induced by stress. Some of these can lead to changes in cell genotype that will allow escape from the stressful condition, and some are neutral.
