Abstract
~ ~~~ A series of thermosensitive cell growth mutants of Enterococcus hirae have been isolated. Most of these mutants elongate and some show reduced autolytic activity when incubated at the non-permissive temperature (42 "C) in comparison to the wild-type incubated at the same temperature. When mutants were incubated for longer than 15 min at 42 "C and were then shifted to 30 "C, a lag proportional to the time of preincubation at 42 "C was observed before division, indicating that a certain time is necessary to restore normal levels of an active molecule(s) needed for septum formation and division. The addition of wild-type muramidase-1 permitted the immediate formation of septa and a single cell division; further addition of the enzyme stimulated the cells to divide once again. The other E. hivae autolytic enzyme, peptidoglycan-hydrolase-2, which is found in the culture medium, seemed to be involved in separation of daughter cells but may also take over the function of muramidase-1. A key role of both enzymes in septum formation and division is postulated.

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