Graduation Semester and Year
Spring 2026
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Quantitative Biology
Department
Biology
First Advisor
Cara Boutte
Abstract
The mycobacterial cell envelope consists of three covalently linked layers whose synthesis must be coordinated to maintain structural integrity during polar growth. While the biosynthetic enzymes for each layer are well characterized, the molecular mechanisms that coordinate synthesis across layers have remained poorly understood. This thesis investigates two essential transmembrane proteins, PgfA and MurJ, that regulate peptidoglycan metabolism in Mycobacterium smegmatis and provide new insight into how mycobacteria synchronize cell wall assembly.
We present evidence that PgfA functions as a bifunctional regulator that links peptidoglycan metabolism to the availability of trehalose monomycolate (TMM), a key mycolic acid precursor. Through epistasis experiments and phosphosite mutagenesis, we show that PgfA's regulatory output depends on both periplasmic TMM levels and post-translational modification of its cytoplasmic C-terminal tail, where individual threonine residues appear to regulate polar peptidoglycan synthesis and overall metabolism. Separately, we identify a regulatory architecture in the essential lipid II flippase MurJ, in which opposing contributions from a periplasmic substrate-binding domain and a cytoplasmic intracellular domain modulate flippase activity. We also correct a previously reported interaction between MurJ and the peptidoglycan regulator CwlM.
Together, these findings argue that coordination of the mycobacterial cell envelope involves a regulatory layer in which dedicated proteins sense metabolite availability and integrate post-translational signals to adjust biosynthetic flux. These mechanisms are largely specific to mycobacteria and related Mycobacteriales and may represent novel targets for antimycobacterial therapeutic development.
Keywords
Mycobacteria, Microbiology, Peptidoglycan, Mycolic acids, MurJ, PgfA, Cell wall coordination, Cell wall synthesis
Disciplines
Bacteriology | Microbial Physiology | Molecular Genetics
License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Recommended Citation
Samaga-de-Tembiwa, Karen Emmanuella, "Coordinating the Layers: Regulation of Peptidoglycan Synthesis and Cell Wall Assembly in Mycobacterium smegmatis by MurJ and PgfA" (2026). Biology Dissertations. 2.
https://mavmatrix.uta.edu/biology_dissertations2/2