At the onset of starvation Escherichia coli undergoes a temporally ordered program of starvation gene expression involving 40-80 genes which some four hours later yields cells possessing an enhanced general resistance. Two classes of genes are induced upon carbon starvation: the cst genes, requiring cyclic AMP, and the pex genes, not requiring this nucleotide for induction. The cst genes are not involved in the development of the resistant state and are concerned with escape from starvation, while the pex gene induction appears to be associated with resistance. Many of the latter are induced in response to a variety of starvation conditions. They include heat shock and oxidation resistance genes, and some utilize minor, stationary-phase-specific sigma factors for induction during starvation. The protective role of stress proteins may be due to their ability to rescue misfolded macromolecules. The starvation promoters can be potentially useful for selective expression of desired genes in metabolically sluggish populations, e.g. in high-density industrial fermentations and in situ bioremediation.