Abstract
Mycobacterial cells elongate via polar deposition of cell wall material, similar to the filamentous Streptomyces species, which contain a tip-organizing centre. Coiled-coiled proteins such as DivIVA play an important role in this process. The genome of Mycobacterium tuberculosis , the causative agent of tuberculosis, encodes many coiled-coil proteins that are homologous to DivIVA with a potential role in mycobacterial cell elongation. Here we describe studies on Mycobacterium smegmatis MSMEG_2416, a homologue of M. tuberculosis Rv2927c. Two previous independent studies showed that MSMEG_2416 was involved in septation (subsequently referred to as sepIVA). Contrary to these previous reports, we found sepIVA to be dispensable for growth in laboratory media by generating a viable null mutant. The mutant strain did, however, show a number of differences, including a change in colony morphology and biofilm formation that could be reversed on complementation with sepIVA as well as Rv2927c, the sepIVA homologue from M. tuberculosis . However, analysis of cell wall lipids did not reveal any alterations in lipid profiles of the mutant strain. Microscopic examination of the mutant revealed longer cells with more septa, which occurred at irregular intervals, often generating mini-compartments, a profile similar to that observed in the previous studies following conditional depletion, highlighting a role for sepIVA in mycobacterial growth.
Highlights
A majority of widely studied rod-shaped bacteria such as Escherichia coli and Bacillus subtilis elongate by the lateral deposition of new cell wall material along the whole length of the bacterium
Homologues of sepIVA were found in the decayed genome of Mycobacterium leprae, in environmental mycobacteria and in other members of the Mycobacterium tuberculosis complex, indicating the presence of this divIVA-like gene across mycobacterial species (Fig. 1a)
These findings suggested that sepIVA represented conserved coiled-c oil proteins that were present in ancestral polar growth progenitors of the Actinomycetales
Summary
A majority of widely studied rod-shaped bacteria such as Escherichia coli and Bacillus subtilis elongate by the lateral deposition of new cell wall material along the whole length of the bacterium. It is the highly regulated septal positioning and formation that results in the formation of morphologically identical daughter cells. DivIVA is responsible for the maintenance of a high concentration of the FtsZ inhibitor, MinC, at the cell poles, ensuring correct positioning of septum formation at the mid cell [3]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
