Peptidoglycan precursor synthesis along the sidewall of pole-growing mycobacteria

Area of Science:

• Microbiology
• Cell Biology
• Biochemistry

Background:

• Mycobacteria exhibit polar growth, but d-amino acid probes indicate peptidoglycan synthesis occurs at both poles and the sidewall.
• The precise metabolic fates and localization of these d-amino acid probes remain unclear.

Purpose of the Study:

• To elucidate the metabolic pathways and localization of d-amino acid probes in mycobacteria.
• To precisely map peptidoglycan metabolism during cell growth and in response to damage.

Main Methods:

• Incorporation of monopeptide and dipeptide d-amino acid probes.
• Assessment of probe incorporation in the presence of antibiotics and in mutant strains affecting peptidoglycan synthesis and l,d-transpeptidation.
• Localization of probe metabolism using fluorescent penicillin.

Main Results:

• Monopeptide incorporation was sensitive to inhibitors of peptidoglycan synthesis and l,d-transpeptidation.
• Dipeptide incorporation was linked to lipid-linked peptidoglycan precursors and complemented synthesis defects.
• Probe localization revealed peptidoglycan synthesis and remodeling at poles, septum, and sidewall, with sidewall synthesis responding to cell wall damage.

Conclusions:

• D-amino acid probes effectively distinguish between peptidoglycan synthesis and remodeling.
• Peptidoglycan synthesis occurs at the poles and septum, associated with elongation, while sidewall synthesis is involved in repair and robustness.
• Sidewall peptidoglycan editing may contribute to cell wall integrity in pole-growing mycobacteria.