Abstract
Escherichia coli rodA mutant AOS151 grows as round cells at 30 and 42°C (H. Matsuzawa, K. Hayakawa, T. Sato, and K. Imahori, J. Bacteriol., 115, 436_??_442 (1973)). The mutant was found to be resistant to mecillinam at both temperatures. lip+ transductants were prepared by PI phage transduction via strain AOS151, the cotransduction frequency of round morphology (rod-) at 42°C with the lip gene being about 90%. At 42°C all 54 rod- transductants tested were resistant to mecillinam. At 30°C all but two of these rod- (at 42°C)-type transductants were rod-shaped, and all were sensitive to mecillinam; the two strains grew as ovoid cells. The original rodA mutant AOS151 probably involves an additional mutation(s), that expresses the round cell shape at lower temperature, whereas the rodA51 mutation alone seems to result in temperature-sensitive expression of round cell morphology and mecillinam resistance. rodA mutant cells cultured at either 30 or 42°C had wild-type penicillin-binding protein 2, judging from penicillin-binding activity, electrophoretic mobility, and thermosensitivity.
