Induction of only limited elongation instead of filamentation by inhibition of cell division in Corynebacterium glutamicum

In order to characterize the cell-division mechanism of coryneform bacteria, we tried to isolate cell-division mutants from Corynebacterium glutamicum after N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis, such as Escherichia coli fts mutants, which form long filaments at the restrictive temperatures. At the nonpermissive temperature; most of the mutants formed club-shaped or dumbbell-shaped, elongated rod cells, but no filament formers were isolated. Then we examined the effects of cell division inhibitors on this organism. Cephalexin and sparfloxacin, which are the inhibitors of septation and DNA synthesis respectively, and are known to cause cell filamentation in E. coli, did not cause filamentation in C. glutamicum but induced morphological changes that were similar to those observed with the temperature-sensitive ts mutants of C. glutamicum. These, results suggest that C. glutamicum has a unique regulation mechanism, that is, the inhibition of cell division leads to cessation of cell elongation.