PhD defence C. (Chinmoy) Saha

Below is a brief summary of the dissertation: 

Keeping DNA safe is vital for the survival of all living organisms. To protect their DNA from both internal and external threats, organisms have developed various defense mechanisms. One significant defense system is known as CRISPR-Cas, which helps bacteria combat harmful mobile genetic elements (MGEs). This system also plays a crucial role in bacterial infection and interactions with more complex organisms, including humans. This thesis examines these roles, primarily focusing on how CRISPR-Cas systems contribute to bacterial infections. A key component of the CRISPR system is the Cas9 protein, which can have a direct impact on human cells. Cas9 has the potential to cause DNA damage, modulate inflammatory pathways, and even lead to cell death. The thesis explains how Cas9 when delivered through outer membrane vesicles, can enter human cells and randomly cut DNA. Furthermore, this research identifies CRISPR-like elements within human DNA that may help distinguish cancerous tissues from healthy ones. It also highlights the diversity of CRISPR-Cas components, which could be beneficial in tracking drug-resistant bacteria. In summary, this thesis enhances our understanding of CRISPR-Cas systems by illustrating their variety, their roles in host interactions, and their potential diagnostics applications while explaining their contribution to bacterial pathogenesis.