Influence of expression of the NgoΦ1 prophage CDS495 and NgoΦ2 CDS1116 encoding the putative repressors on production of the phage λ. E. coli 3102 (λ
). Cells carrying cloned CDS479 or CDS1116 were grown overnight at 30°C and then diluted 1:50 in the fresh LB medium. The growth was continued for 3 hr at 30°C. At that time the culture was divided and the expression of the cloned gene was induced by the addition of the arabinose to a final concentration of 0.001%. After 45 min of growth at 30°C the cultures were heat induced at 43°C for 15 min and then the growth was continued at 37°C. The samples were withdrawn at different times and the optical density (A) and (B) the free phage titer (after treatment with chloroform, 10% final concentration for 15 min) were determined. Symbols: (filled circles) E. coli 3102 (λcI857) (pMPMK6) cells no arabinose was added; (open circles) E. coli 3102 (λcI857) (pMPMK6) cells induced with arabinose; (open triangles), E. coli 3102 (λcI857) (pMPMK6::cds1116) no arabinose added; (filled triangles) E. coli 3102 (λcI857) (pMPMK6::cds1116) cells induced with arabinose; (open squares), E. coli 3102 (λcI857) (pMPMK6::cds479) no arabinose added; and (filled squares), E. coli 3102 (λcI857) (pMPMK6::cds479) cells induced with arabinose. The arrow shows the time when the heat induced cultures were transferred into 37°C.