Escherichia coli produces several membrane-associated and periplasmic proteins in response to deprivation for a carbon source. The carbon starvation response involves a two- to fourfold, cAMP-dependent induction of operons involved in carbohydrate uptake and utilization, including the lac operon. Three carbon-starvation-inducible (csi) gene fusions to a phoA reporter sequence were characterized. The phoA-fusions were cya+/crp+-dependent and located in three previously characterized genes involved in high-affinity uptake of alternative carbon sources: mglB, encoding the periplasmic galactose binding protein; rbsB, encoding the periplasmic ribose binding protein; and lamB, encoding the maltodextrin-specific outer membrane porin.