A Multifaceted Study on Vibrio cholerae: Exploring the Roles of CgtA and a putative phosphodiesterase

Kejriwal, Kumari Shristi (2025) A Multifaceted Study on Vibrio cholerae: Exploring the Roles of CgtA and a putative phosphodiesterase. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Kumari Shristi Kejriwal (20MS114)) 20MS114_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (3MB)

Abstract

Cholera, an acute diarrheal disease caused by the bacterium Vibrio cholerae is a major worldwide health concern, particularly in developing countries with poor sanitation and limited access to clean water. The pathogenesis of Vibrio cholerae involves a number of intricate processes, such as- the formation of biofilms and the production of virulence factors like Toxin Co-regulated Pilus and Cholera Toxin which are crucial for causing the disease and spreading the infection. The bacteria’s capacity to colonize the host and cause the disease depends on the complex regulation of these processes. This study investigates the roles of a putative phosphodiesterase- Q9KRD2 and CgtA, both of which have been hypothesized to be important in Vibrio cholerae pathophysiology. The putative phosphodiesterase- Q9KRD2 has been found to be involved in the signalling of c-di-GMP, a second messenger that regulates several key processes in the bacteria. cgtA, an essential gene in the bacteria encodes for a GTPase protein that plays a role in ribosome biogenesis, stress response, and adaptation to environmental changes. We tried to integrate molecular biology and computational biology in order to understand the effect that a particular site-directed mutation has on the wild-type putative phosphodiesterase- Q9KRD2. Additionally, we studied the CgtA protein using a number of biochemical assays to compare the wild type and cgtA knockdown strain of Vibrio cholerae. The study was carried out using the Vibrio cholerae El Tor N16961 strain. Our key findings include that the E450K mutation in Q9KRD2 alters the protein's flexibility (in the loop region), affecting its interaction with its ligand- c-di-GMP. The knockdown of cgtA resulted in pleiotropic effects in the bacteria. Notably, the cgtA knockdown strain showed a shift towards prioritizing colonization over acute virulence.

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