Distinct Spatiotemporal Dynamics of Peptidoglycan Synthesis between Mycobacterium smegmatis and Mycobacterium tuberculosis

Abstract

Peptidoglycan (PG), a polymer cross-linked by d-amino acid-containing peptides, is an essential component of the bacterial cell wall. We found that a fluorescent d-alanine analog (FDAA) incorporates chiefly at one of the two poles in Mycobacterium smegmatis but that polar dominance varies as a function of the cell cycle in Mycobacterium tuberculosis: immediately after cytokinesis, FDAAs are incorporated chiefly at one of the two poles, but just before cytokinesis, FDAAs are incorporated comparably at both. These observations suggest that mycobacterial PG-synthesizing enzymes are localized in functional compartments at the poles and septum and that the capacity for PG synthesis matures at the new pole in M. tuberculosis. Deeper knowledge of the biology of mycobacterial PG synthesis may help in discovering drugs that disable previously unappreciated steps in the process.

DivIVA concentrates mycobacterial cell envelope assembly for initiation and stabilization of polar growth

“…Fluorescent DivIVA foci persist upon spheroplasting (Supporting Information Figure S2). (Botella et al, 2017;Meniche et al, 2014). (Botella et al, 2017;Meniche et al, 2014).…”

“…The genomic context of divIVA (wag31) also supports a role in envelope homeostasis, as the gene is located in a cluster that also encodes many key enzymes in peptidoglycan metabolism (Kang et al, 2008). Phosphorylation, overexpression or tagging of DivIVA correlates with changes to the sites of peptidoglycan synthesis and cell growth (Botella et al, 2017;Hamasha et al, 2010;Jani et al, 2010;Kang et al, 2008;Meniche et al, 2014;Nguyen et al, 2007). However, they were unable to determine whether peptidoglycan synthesis was absent or simply dispersed (Kang et al, 2008).…”

“…Actinobacteria, including the pathogen Mycobacterium tuberculosis and the model organism Mycobacterium smegmatis, synthesize peptidoglycan predominantly at the cell poles (Daniel & Errington 2003;Thanky et al, 2007). Mycobacterial elongation is asymmetric; extension of the old pole is more rapid than that of the new pole (Aldridge et al, 2012;Botella et al, 2017;Joyce et al, 2012;Meniche et al, 2014;Rego et al, 2017;Singh et al, 2013;Siegrist et al, 2015). The mycobacterial cell envelope includes additional, covalently attached layers that are not found in other genera, including the glycoconjugate arabinogalactan and the mycolic acids that comprise the mycomembrane (Jankute et al, 2015).…”

“…DivIVA marks the tips of mycobacterial cells and is found in higher concentrations at the older, faster growing pole (Botella et al, 2017;Kang et al, 2008;Meniche et al, 2014;Nguyen et al, 2007).…”

“…However, they were unable to determine whether peptidoglycan synthesis was absent or simply dispersed (Kang et al, 2008). Phosphorylation, overexpression or tagging of DivIVA correlates with changes to the sites of peptidoglycan synthesis and cell growth (Botella et al, 2017;Hamasha et al, 2010;Jani et al, 2010;Kang et al, 2008;Meniche et al, 2014;Nguyen et al, 2007). Although the phosphorylation status of DivIVA impacts peptidoglycan precursor synthesis, a direct, physical interaction between the synthetic enzymes and DivIVA has not been detected, making it unclear if DivIVA directly regulates their activity .…”