In vitro and in vivo studies of cyclic di-GMP signaling proteins

• Main Author: Chuah, Mary Lay Cheng
• Other Authors: Liang Zhao-Xun
• Format: Theses and Dissertations
• Language: English
• Published: 2014
• Subjects: DRNTU::Science::Biological sciences::Biochemistry; DRNTU::Science::Biological sciences::Microbiology::Bacteria; DRNTU::Science::Biological sciences::Molecular biology; DRNTU::Science::Biological sciences::Microbiology::Microorganisms
• Online Access: http://hdl.handle.net/10356/60502
• Institution: Nanyang Technological University

Cyclic di-GMP is a bacterial secondary messenger important for the regulation of biofilm formation and bacterial pathogenesis. Although much progress has been made in recent years, many questions about the hierarchical and complex cyclic di-GMP signaling networks remain to be answered. With only a relatively small number of cyclic di-GMP signaling proteins, Bacillus subtilis serves as a simple and genetically tractable model organism for us to study cyclic di-GMP signaling. We identified two catalytically active diguanylate cyclases (DGC), one phosphodiesterase (PDE) and one bifunctional enzyme. Phenotypic analysis revealed the regulatory roles of these proteins in bacterial motility, sporulation and biofilm formation. In addition, a few representative GGDEF-EAL didomain proteins with known input signals were nvestigated to understand how the GGDEF or EAL domain is regulated by its associated N-terminal regulatory domain. The catalytic activities of the AxDGC2 and AxPDEA2 proteins from Gluconacetobacter xylinus were found to be modulated by the flavin and heme-associated PAS domain respectively; while the Tbd_1269 protein from the Thiobacillus denitrificans was found to possess both DGC and PDE activities that are likely to be regulated by phosphorylation of the N-terminal regulatory domain.