Improved bacterial SOS promoter:: lux fusions for genotoxicity detection

Escherichia coli strains containing plasmid-borne fusions of Vibrio fischer i lux to the recA promoter-operator region were previously shown to be pote ntially useful for detecting genotoxicants. In an attempt to improve past p erformance, the present study examines several modifications and variations of this design, singly or in various combinations: (1) modifying the host cell's toxicant efflux capacity via a tolC mutation; (2) incorporating the lux fusion onto the bacterial chromosome, rather then on a plasmid; (3) cha nging the reporter element to a different lux system (Photorhabdus luminesc ens), with a broader temperature range; (4) using Salmonella typhimurium in stead of an E. coli host. A broad spectrum of responses to pure chemicals a s well as to industrial wastewater samples was observed. Generally, fastest responses were exhibited by Sal94, a S. typhimurium strain harboring a pla smid-borne fusion of V. fischeri lux to the E. coli recA promoter. Highest sensitivity, however, was demonstrated by DPD3063, an E. coli strain in whi ch the same fusion was integrated into the bacterial chromosome, and by DPD 2797, a plasmid-bearing tolC mutant. Overall, the two latter strains appear ed to perform better and seemed preferable over the others. The sensor stra ins retained their sensitivity following a 2-month incubation after alginat e-embedding, but at the cost of a significantly delayed response. (C) 2000 Elsevier Science B.V. All rights reserved.