Characterization of a cold-resistant mutant of Escherichia coli

Abstract

Using an Escherichia coli cold-resistant transductant MET6 and its parent MET3, which are isogenic except for the cold resistance gene, the effects of low temperature on the growth, viability, and cell morphology in nutrient broth or on nutrient agar medium were compared. The minimal growth temperatures of strains MET3 and MET6 were found to be in the vicinity of 12°C and 7°C, respectively. Remarkable and rapid loss of viability was observed in strain MET3 at temperatures between 8°C and 10°C, just below the minimal growth temperature. Considerable elongation of the cells of this strain was observed at these temperatures. However, strain MET6 was able to grow normally at and above 7°C. Transduction experiments were also performed to determine the precise map position of the mutated locus. The results indicate that the cold-resistance gene is located very close to the tdk gene at 27.5 min, i.e. between the hemA and trpB loci on the E. coli chromosome, that it plays an important role in growth at low temperature, and is possibly involved in determining the minimal growth temperature and cell morphology of E. coli.