Role of nalidixic acid in isolation ofSalmonella typhimurium strains capable of growth at 48°C

Abstract

Salmonella typhimurium thermotolerant mutants dependent on the presence of nalidixic acid for growth at 48 degrees C were isolated and designated nalidixic acid-dependent, thermotolerant mutants, naldttl. Genetic mapping revealed that naldttl alleles map within the gyrA gene. When S. typhimurium strain Q was plated in the dark on nutrient agar containing nalidixic acid (20 micrograms/ml) as a photosensitizer and briefly exposed to white light or near VU light prior to incubation at 42 degrees C, nalidixic acid-resistant mutants arose in about 16 h at frequencies of 5 x 10(-8) for white light and 1 x 10(-6) for near UV light. About 10% of these nalidixic acid-resistant mutants derived from photodynamic mutagenesis exhibited the thermotolerant characteristic.

Increased thermosensitivity associated with topoisomerase I deletion and promoter mutations inEscherichia coli

“…The results shown here indicate that the mutations reducing or eliminating topoisomerase I activity can result in increased thermosensitivity in E. coli . This correlates with the findings that mutations in the gyrA gene can lead to increased thermoresistance [8–10]. DNA supercoiling has been shown to be about 12% less negative in one of these gyrA mutants than in the parental strain [10].…”

“…There is growing evidence that DNA topoisomerases can influence the ability of bacteria to grow or survive at high temperatures. Involvement of gyrase has emerged from the isolation of a number of thermoresistant mutants of Escherichia coli and S. typhimurium that have been found to have mutations within the gyrA gene for the A subunit of DNA gyrase [8–10]. Among the four promoters utilized for transcription initiation of the topoisomerase I ( topA ) gene of E. coli , the P1 promoter has been shown to be a σ 32 ‐dependent heat shock promoter [11–13].…”

Topoisomerase function during bacterial responses to environmental challenge

“…Characterization of mutations in E. coli and S. typhimurium that allow growth at 48 o C revealed mutations in the gyrA gene (75)(76)(77). The addition of the gyrase inhibitor nalidixic acid to the growth medium after prolonged incubation of E. coli and S. typhimurium at 48 o C in one such study selected for gyrA mutants that are in addition to high temperature resistant, nalidixic aciddependent for growth (75,76). In a second study, a spontaneous nalidixic acid-resistant and thermoresistant gyrA mutant of E. coli was isolated and found to have approximately 12% less negative DNA supercoiling than the parental strain (77).…”

Isolation of Salmonella resistant to hypochlorous acid from a poultry abattoir

“…Several antimicrobial agents, such as antibiotics, bacteriocins, organic acids, oxidizing agents and high temperatures, have been used individually or in combination in an attempt to eradicate or decrease the numbers of food-borne pathogens (Droffner and Yamamoto 1992;Mendonca et al 1994;Radford and Board 1995). However, over time, micro-organisms may develop tolerance or become resistant to these biocides (Russell et al 1997).…”