Date of Award
2021
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Biology
Abstract
While humans are the only known reservoir for Streptococcus pyogenes , streptococcal diseases are still a major global health problem because there is no effective commercial vaccines (Carapetis, et al., 2005). A comprehensive understanding of the signaling pathway that regulates virulence and host immune response needs to be resolved in order to develop vaccines and drugs. Previously it was reported that cyclic-di-AMP (c-di-AMP), a second messenger molecule, regulates cell wall stability and virulence in S. pyogenes (Cho & Kang, 2013). The appropriate intracellular c-di-AMP level is necessary for their functions that are regulated by synthesizing enzymes, di-adenylate cyclase (DACs), and degradation enzyme, phosphodiesterases (PDEs). S. pyogenes encodes one diadenylate cyclase, DacA, which converts ATP to c-di-AMP and two phosphodiesterases, GdpP and Pde2. We hypothesized that dysregulation of intracellular c-di-AMP levels by manipulating the dacA, gdpP , and pde2 genes would give us insight into the c-di-AMP-dependent regulation that controls cell physiologies and pathogenesis in S. pyogenes . In this study, we identified that c-di-AMP regulates critical cellular functions, including antibiotic susceptibility and stress responses in S. pyogenes . We also elucidated that major virulence activities in this bacterium such as SpeB protease expression, hemolysis, and biofilm formation activity are regulated by the c-di-AMP signaling pathway. Further, we utilized a transposon mutagenesis assay to discover the potential genes involved in c-di-AMP secretion. Based on the screening of the mutants of ∆GdpP, a gdpP deletion mutant with low c-di-AMP secretion ability, we identified FasB, a three-component regulatory system member, as a potential regulator for the secretion of c-di-AMP. Using an insertional disruption mutation technique, the genes of FasB and a multidrug transporter were disrupted and confirmed that they are involved in c-di-AMP secretion. Further research needs to be performed to identify their specific roles in c-di-AMP secretion by S. pyogenes .
Recommended Citation
Fahmi, Tazin, "The Second Messenger Molecule Cyclic Di Amp Regulates Physiologies And Pathogenesis In Streptococcus Pyogenes" (2021). All-Inclusive List of Electronic Theses and Dissertations. 2157.
https://scholars.indianastate.edu/etds/2157