Genetic evidence that mycobacterial FtsZ and FtsW proteins interact, and colocalize to the division site in Mycobacterium smegmatis

We provide genetic evidence to show that the Mycobacterium tuberculosis FtsZ and FtsW proteins interact, and that these interactions are biologically relevant. Furthermore, we show by fluorescence microscopy that Mycobacterium smegmatis FtsW is part of its septasomal complex and colocalizes with FtsZ to the midcell sites. Colocalization experiments reveal that approximately 27% of the cells with septal Z-rings contain FtsW whereas 93% of the cells with FtsW bands are associated with FtsZ indicating that FtsW is late recruit to the septum, as in Escherichia coli. Our results suggest that mycobacterial FtsZ can localize to the septum independent of FtsW, and that interactions of FtsW with FtsZ are critical for the formation of productive FtsZ-rings and the cell division process in mycobacteria.