Cold-sensitive mutation of Pseudomonas putida affecting enzyme synthesis at low temperature.

A cold-sensitive mutant of Pseudomonas putida has been isolated which grows normally at 30 C but is unable to grow on mandelate as a source of carbon at 15 C. The mutation results in the inability of the strain to carry out the reaction catalyzed by cis,cis-muconate lactonizing enzyme at low temperature and must lie in the structural gene for that enzyme, because the mutant enzyme produced at 30 C shows altered thermal stability. The mutant enzyme is not intrinsically cold-labile, nor is it cold-labile at the moment of synthesis. The activity of the mutant enzyme is not inhibited at low temperature. Evidence is presented to establish that this mutation in the structural gene coding for cis,cis-muconate lactonizing enzyme results in the lack of expression of that gene at low temperature.