Melanie Blokesch: Once the pathogen becomes the host: How Vibrio cholerae defends against mobile genetic elements

May 5, 2025

Location:

In person: MIT 56 Room 180

Zoom Alternative: https://mit.zoom.us/j/99149489205

Professor Melanie Blokesch, Swiss Federal Institute of Technology Lausanne (EPFL) in Switzerland

Monday, May 5th, 4:00pm – 5:00pm

Summary: Cholera, caused by the intestinal pathogen Vibrio cholerae, remains a major global health concern, with the ongoing seventh pandemic driven by the O1 El Tor lineage. While host-related virulence mechanisms are well studied, the molecular strategies that V. cholerae employs to defend against mobile genetic elements (MGEs) are less well understood. Recent work has revealed that pandemic strains encode multiple defense systems targeting both plasmids and phages, many of which are located on hallmark pathogenicity islands. In this talk, I will present how two DNA defense modules (Ddm) cooperate to degrade small multi-copy plasmids and inhibit the spread of large conjugative plasmids through self-inflicted cellular suicide. I will also share new findings on the West African South American (WASA) sublineage of pandemic V. cholerae, which harbors unique MGEs encoding sophisticated anti-phage defense systems. Together, these diverse and layered strategies likely contributed to the evolutionary success and global dissemination of the seventh pandemic lineage.

Bio: Melanie Blokesch is a Full Professor at the Swiss Federal Institute of Technology Lausanne (EPFL) in Switzerland. Her research focuses on understanding the complex evolutionary pathways of bacteria in natural environments, particularly their transition into human pathogens. She primarily investigates Vibrio cholerae, the causative agent of cholera, and Acinetobacter baumannii, a nosocomial pathogen. Dr. Blokesch earned her PhD from Ludwig Maximilians University Munich and conducted postdoctoral research at Stanford University before joining EPFL in 2009 as Head of the Laboratory of Molecular Microbiology. Since 2022, she has served as Director of the Global Health Institute at EPFL. She is currently on sabbatical leave at Harvard Medical School during Spring and Summer 2025.