Characterizing the role of central carbon metabolism and cell wall stress responses in Bacillus subtilis cell wall synthesis
The cell wall is an essential organelle for many bacteria since it provides mechanical strength and prevents bacterial cell lysis due to internal turgor pressure. Additionally, the cell wall is the first line of defense against various external stresses. The mesh of peptidoglycan is a major component of bacterial cell wall that surrounds the outer membrane. The cell wall of the gram-positive rod-shaped bacterium Bacillus subtilis consists of a thick peptidoglycan (PG) layer and phosphate containing anionic polymers called teichoic acids. To maintain the rod shape, B. subtilis elongates its lateral cell wall first, followed by cell division. Both tasks are carried out by distinct but coordinated machineries termed as elongasome (also termed as the Rod complex) and divisome, respectively. The synthesis of peptidoglycan is a dynamic process that is affected by various factors such as the availability of nutrients and external stresses. I have characterized the physiological role of an essential gluconeogenic factor GlmR (previously known as YvcK) in B. subtilis. Homologs of GlmR present in bacteria from different phyla and preliminary observations hint towards a conserved role of GlmR in different organisms. Except the phenotypic observations, for a long-time the function of GlmR has been a mystery. In my dissertation, I show that GlmR functions at the interface of the central carbon metabolism and the peptidoglycan biosynthesis pathway. I have discovered that under gluconeogenic growth condition, GlmR plays an essential role in diverting carbon from the central carbon metabolism to the peptidoglycan biosynthesis, putatively by activation of GlmS- the first enzyme in PG precursor biosynthesis. Additionally, I have studied a B. subtilis signaling nucleotide, cyclic diadenosine monophosphate (c-di-AMP), and an extracytoplasmic function (ECF) σ-factor, σM, in peptidoglycan homeostasis in response to beta-lactam stress. GlmR as well as c-di-AMP are known to be important for virulence in many pathogenic bacteria. GlmR is essential for establishing infection in Listeria monocytogenes and Mycobacterium tuberculosis. Many pathogens use c-di-AMP to modulate the host immune system to facilitate the infection. Taken together, this dissertation adds to the current understanding of the effects of nutrient availability and stress on peptidoglycan homeostasis in B. subtilis which can be further applied to understand bacterial virulence.
Beta-lactam; Gluconeogenesis; moonlighting enzyme; Genetics; Microbiology; Molecular biology; Metabolism; Bacillus subtilis; Peptidoglycan
Helmann, John D.
Alani, Eric E.; Sondermann, Holger
Ph. D., Microbiology
Doctor of Philosophy
dissertation or thesis