Delineating FtsQ-mediated regulation of cell division in Mycobacterium tuberculosis

Abstract

Identifying and characterizing the individual contributors to bacterial cellular elongation and division will improve our understanding of their impact on cell growth and division. Here, we delineated the role of , a terminal gene of the highly conserved division cell wall () operon, in growth, survival, and cell length maintenance in the human pathogen (). We found that FtsQ overexpression significantly increases the cell length and number of multiseptate cells. FtsQ depletion in resulted in cells that were shorter than WT cells during the initial growth stages (4 days after FtsQ depletion) but were longer than WT cells at later stages (10 days after FtsQ depletion) and compromised the survival and in differentiated THP1 macrophages. Overexpression of N- and C-terminal FtsQ regions altered the cell length, and the C-terminal domain alone complemented the FtsQ depletion phenotype. MS analyses suggested robust FtsQ phosphorylation on Thr-24, and although phosphoablative and -mimetic mutants rescued the FtsQ depletion-associated cell viability defects, they failed to complement the cell length defects. MS and coimmunoprecipitation experiments identified 63 FtsQ-interacting partners, and we show that the interaction of FtsQ with the recently identified cell division protein SepIVA is independent of FtsQ phosphorylation and suggests a role of FtsQ in modulating cell division. FtsQ exhibited predominantly septal localization in both the presence and absence of SepIVA. Our results suggest a role for FtsQ in modulating the length, division, and survival of cells both and in the host.

A mycobacterial DivIVA domain-containing protein involved in cell length and septation

“…However, despite the differences in reports of essentiality, the rest of our studies report similar phenotypes to the conditional mutants characterized in these previous studies, particularly the elongated cells and altered septation patterns. Thus, this work, along with the previous findings of Wu et al [14] and Jain et al [15], does identify a key role for sepIVA in septation and warrants further studies to decipher its precise role.…”

“…It is unlikely that downstream effects on MSMEG_2417 might have led to a different outcome of essentiality in these two studies, as MSMEG_2417 is not essential in M. smegmatis [26]. Moreover, the conditional mutants described in these studies showed similar phenotypes to WT M. smegmatis under conditions that allowed for expression of SepIVA function [14,15]. Rv2927c is predicted to be essential in M. tuberculosis, but M. smegmatis can tolerate the loss of genes known to be essential in M. tuberculosis.…”

“…We were able to generate a viable null mutant of M. smegmatis sepIVA to help us address the role of this gene in mycobacterial growth. During the course of this study, two independent reports on mycobacterial septal factors were published [14,15], outlining a role for sepIVA in septum formation in mycobacterial cells. Contrary to our studies, both studies reported sepIVA as an essential gene in M. smegmatis.…”

“…We further investigated possible factors that may have affected our ability to obtain a viable sepIVA mutant, contrary to the earlier reports of essentiality. The two previous studies used 7H9 and 7H10 for growth [14,15], while we used TSB agar to select for transductants. To probe potential effects of media, we tested the ability of the ΔsepIVA strain to grow on plates of three Middlebrook media, 7H9+agar, 7H10 and 7H11, compared to TSB agar.…”

The NtrYX Two-Component System Regulates the Bacterial Cell Envelope

“…In other organisms, loss of any of these fts genes blocks division completely, leading to long filamentous cells or loss of viability (21). However, decreased levels of these genes cause more moderate phenotypes, in particular, depletion of either ftsA or ftsQ leads to increased cell length in other bacteria (40,41), similar to the longer length observed in ΔntrYX cells that have twofold lower levels of ftsA and ftsQ transcripts ( Table 1). Thus, it is likely that direct regulation of cell division genes in the dcw cluster contributes to the slowed initiation and progression of cell division, decreased grown rate, and altered cell shape of the NtrYX mutant.…”