MINCD PROTEINS CONTROL THE SEPTATION PROCESS DURING SPORULATION OF BACILLUS-SUBTILIS

Mutation of the divIVB locus in Bacillus subtilis causes misplacement of the septum during cell division and allows the formation of anuclea te minicells, The divIVB locus contains five open reading frames (ORFs ). The last two ORFs (minCD) are homologous to minC and minD of Escher ichia coil but a minE homolog is lacking in B. subtilis, There is some similarity between minicell formation and the asymmetric septation th at normally occurs during sporulation in terms of polar septum localiz ation. However, it has been proposed that MinCD has no essential role in sporulation septum formation. We have used electron microscopic stu dies to show septation events during sporulation in some minD strains. We have observed an unusually thin septum at the midcell position in minD and also in minD spoIIE71 mutant cells. Fluorescence microscopy a lso localized a SpoIIE-green fluorescent protein fusion protein at the midcell site in minD cells. We propose that the MinCD complex plays a n important role in asymmetric septum formation during sporulation of B. subtilis cells.