FIG. 4.

Properties of strain LIT1 of Acinetobacter strain ADP1 obtained by SDR. The lysis cassette in this strain is under transcriptional control of rRNA operon promoters. (A) Release of DNA from LIT1 cells induced by tetracycline. Cells at an OD₆₀₀ of 0.2 were grown for 2 h with the indicated concentrations of tetracycline. Culture densities (OD₆₀₀ [diamonds]) and the amount of released DNA (bars) are indicated. (B) Induction of DNA release from LIT1 cells by translational inhibitors. Antibiotics were added to exponentially growing LIT1 cells at an OD₆₀₀ of 0.4 at their respective MICs determined for wild-type Acinetobacter. DNA was isolated from the medium after 2 h of incubation and separated by agarose gel electrophoresis. Con, control; Lin, linezolid; Chl, chloramphenicol; FusA, fusidic acid; Cli, clindamycin; Tet, tetracycline; Ery, erythromycin. (C) Northern blot analysis of the expression of the lysis cassette in strain LIT1 incubated for 20 min either without (−) or with (+) erythromycin at 3 μg/ml. The gel stained with ethidium bromide (EtBr) shows that the amounts of RNA in both lanes were equal. The Northern blot hybridization (³²P) with radiolabeled probe corresponding to the Rz gene reveals erythromycin-induced overexpression of the lysis cassette.