The growth of mycobacterial cells requires successful coordination between elongation and septation. However, it is not clear which factors mediate this coordination. Here, we studied the function and post‐translational modification of an essential division factor, SepIVA, in Mycobacterium smegmatis. We find that SepIVA is arginine methylated, and that alteration of its methylation sites affects both septation and polar elongation of Msmeg. Furthermore, we show that SepIVA regulates the localization of MurG and that this regulation may impact polar elongation. Finally, we map SepIVA's two regulatory functions to different ends of the protein: the N‐terminus regulates elongation while the C‐terminus regulates division. These results establish SepIVA as a regulator of both elongation and division and characterize a physiological role for protein arginine methylation sites for the first time in mycobacteria.

Growth of mycobacterial cells requires successful coordination between elongation and division of the cell wall. However, it is not clear which factors directly mediate this coordination. Here, we studied the function and post-translational modification of an essential division factor, SepIVA, in Mycobacterium smegmatis. We find that SepIVA is arginine methylated, and that these modifications alter both division and polar elongation of Msmeg. Furthermore, SepIVA impacts the localization of MurG. Polar localization of MurG correlates with polar elongation in arginine methylation mutants of sepIVA. These results establish SepIVA as a regulator of both elongation and division, and characterize a physiological role for protein arginine methylation for the first time in bacteria.