1992 Volume 38 Pages 104-108
E. coli cold resistant growth (Crg) mutants, MET 1 and MET 2, having the ability to grow at 7.5℃, were isolated from E. coli strain K-12 which shows rapid loss of viability under the same condition (cold sensitive growth, Csg). Strain MET 3, the trp B derivative of stain K-12 constructed by genetic manipulation using strain PA3092 as a donor of genetic markers, showed remarkable and rapid loss of viability at temperatures between 8 and 10℃ (cold super sensitive, Css). Cell elongation was observed at these temperatures of cell death, while strain MET6 constructed from MET3 by transduction using MET1 (crg-1) as a donor was able to grow normally at and above 7℃. The crg gene (s) was located very close to the tdk gene at 27.5 min on E. coli chromosome by the conjugation and transduction experiments. The gene responsible for the Css phenotype was deduced to be identical or very close to the crg locus. The DNA fragment which complemented the Css phenotype of MET3 was cloned from E. coli wild-type strain. The complementing DNA, adjacent to thymidine kinase-like gene, was found to encode histone-like protein H-NS. The role of H-NS gene in pleiotropic regulation was discussed.
