SUMMARY: Autolysis of exponential-phase cells was promoted by pretreating the bacteria (freezing-thawing; −70 °C) in Tris buffer, followed by incubation at 37 °C in the same buffer. The effect was dependent on Tris concentration. The pretreatment provoked ultrastructurally visible damage with extensive loss of K and leakage of UV-absorbing components. No autolysis was observed when the bacteria frozen-thawed in Tris were incubated in the presence of the autolysin inhibitor -bromosuccinimide nor when they had been grown in the presence of chloramphenicol or tetracycline. Furthermore, two autolytic-defective mutants, EC31 and EC78, isolated from , did not autolyse when frozen-thawed and incubated in Tris. Freezing-thawing in Tris, however, imparted extensive cell damage to the mutants and to the antibiotic-treated bacteria as well as considerable leakage of K and UV-absorbing materials. These observations indicate that the lysis of reported above is due to the activity of the endogenous bacterial autolysin. Induction of autolysis of by freezing-thawing was also observed, although to a lesser extent, when Tris was replaced by imidazole.


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