Competence (correspondence, Teruo Tanaka)

 

     Mutants grown overnight in Antibiotic medium 3 is diluted 20 fold in 5 ml of Modified Competence medium (Kunst et al, Regulation of bacterial differentiation pp.1-20. P. J. Piggot, C. P. Moran, Jr., and P. Youngman (ed.). American Society for Microbiology, Washington D.C. 1994), and incubated for 6 hours. Chromosomal DNA carrying cat at the aprE locus is added to 0.5 ml of the competent cells, and the mixture incubated for 50 minutes. Then, four vol of Antibiotic medium 3 are added, and after 2 hours of incubation cells are spread on LB plates containing 5 μg/ml of chloramphenicol. For the cells showing slower growth the turbidities are measured at hourly intervals and competennt cells were obtained 1 hour after the cessation of the exponential growth.