Date of Award
Spring 2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Microbiology
First Advisor
Rego, Hesper
Abstract
From dividing labor within communities to having a flexible response to environmental insults, phenotypic heterogeneity provides numerous benefits to microorganisms. Mycobacteria create this heterogeneity, in part, by their unique pattern of asymmetric growth and division, which generates a population of cells that varies in size, growth rate, and antibiotic susceptibility (1). The deletion of a single gene conserved exclusively in mycobacteria, known as lamA, abrogates a significant amount of this heterogeneity (2). We set out to characterize this protein of relatively unknown function using a combination of genetics, biochemistry, live cell time-lapse microscopy, and super-resolution microscopy.We show that LamA coordinates multiple proteins responsible for growth of new cell envelope material and division of daughter cells. LamA helps maintain the uneven distribution of cell envelope proteins including Wag31, MmpL3, MurJ, and the previously uncharacterized PgfA. Investigation of PgfA through time-lapse microscopy and lipid profiling, demonstrated that outer membrane synthesis drives elongation at the old pole, that PgfA is responsible for trafficking the outer membrane lipid TMM, and that altering TMM levels shifts the dependance to other lipid moieties for envelope integrity. Next, we describe that regulation of many key growth and division proteins is accomplished by differential localization via phosphorylation state, thereby altering the dynamics of cell wall biogenesis. We also found that LamA functionally interacts with proteins in the electron transport chain, despite these proteins being excluded from the tips of the cell. We demonstrate that deletion of lamA leads to more uniformity in the localization of respiratory complexes, membrane potential, and ATP concentration between daughter cells. Together, our data support a model in which LamA functions to spatiotemporally coordinate two essential systems: cell growth and respiration. Through this coupling, LamA represents a key factor in mycobacterial physiology, and further characterization of its role may broaden our understanding of why mycobacteria are outliers amongst other rod-shaped bacteria.
Recommended Citation
Gwin, Celena, "Investigating the cellular role of LamA phosphorylation on asymmetric polar growth in mycobacteria" (2024). Yale Graduate School of Arts and Sciences Dissertations. 1354.
https://elischolar.library.yale.edu/gsas_dissertations/1354
