Bacterial pathogens threaten both human and animal health. Bacteria have developed powerful and diverse biological weapons to infect hosts. Examples include section systems for injection bacterial and proteins into host cells, toxins that alter cellular functions, and enzymes that highjack host signaling pathways. The Ohi lab uses a combination of biochemistry and structural biology techniques to study the structure and function of the complex molecular machines that bacteria have evolved to infect hosts. This seminar will focus on our recent work characterizing Type IV Secretion Systems and pore forming toxins from Gram negative pathogens using cryo-EM.