MinCD Proteins Control the Septation Process during Sporulation of Bacillus subtilis
ABSTRACT Mutation of the divIVB locus in Bacillus subtilis causes misplacement of the septum during cell division and allows the formation of anucleate minicells. The divIVBlocus contains five open reading frames (ORFs). The last two ORFs (minCD) are homologous to minC andminD of Escherichia coli but a minEhomolog is lacking in B. subtilis. There is some similarity between minicell formation and the asymmetric septation that normally occurs during sporulation in terms of polar septum localization. However, it has been proposed that MinCD has no essential role in sporulation septum formation. We have used electron microscopic studies to show septation events during sporulation in some minDstrains. We have observed an unusually thin septum at the midcell position in minD and also in minD spoIIE71mutant cells. Fluorescence microscopy also localized a SpoIIE-green fluorescent protein fusion protein at the midcell site inminD cells. We propose that the MinCD complex plays an important role in asymmetric septum formation during sporulation ofB. subtilis cells.