PROLONGED ENVIRONMENTAL-STRESS VIA A 2 STEP PROCESS SELECTS MUTANTS OF ESCHERICHIA, SALMONELLA AND PSEUDOMONAS THAT GROW AT 54-DEGREES-C

A prolonged incubation of Escherichia, Salmonella or Pseudomonas at 48-degrees-C with nalidixic acid selected mutants (T48) able to grow at 48-degrees-C. A prolonged incubation at 54-degrees-C of the T48 mutants selected mutants (T54) able to grow at 54-degrees-C. These mutants were susceptible to the same bacteriophages as the original mesophilic strains. Auxotrophic phenotypes of Escherichia coli and Salmonella typhimurium mesophilic parents were demonstrated by these mutants if they were cultivated on minimal agar with cellobiose at 48-degrees-C or 54-degrees-C or on a minimal agar with glucose at 37-degrees-C. The T48 alleles mapped in the gyrA region of E. coli or S. typhimurium chromosome. In S. typhimurium the T54 alleles, which permit growth at 54-degrees-C, were shown by cotransductional analysis to be linked to gyrA.