Toxic Waste Disposal in Escherichia coli

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Abstract
About 10% of the nalidixic acid-resistant (Nal r ) mutants in a transposition-induced library exhibited a growth factor requirement as the result of cysH , icdA , metE , or purB mutation. Resistance in all of these mutants required a functional AcrAB-TolC efflux pump, but the EmrAB-TolC pump played no obvious role. Transcription of acrAB was increased in each type of Nal r mutant. In the icdA and purB mutants, each of the known signaling pathways appeared to be used in activating the AcrAB-TolC pump. The metabolites that accumulate upstream of the blocks caused by the mutations are hypothesized to increase the levels of the AcrAB-TolC pump, thereby removing nalidixic acid from the organism.