Bacterial Virulence Mechanisms PDF

Example 1: The Type III secretion system Example 1: The Type III secretion system  Example 2: The Type VI secretion system The Type VI Secretion System is akin to a “stabbing devic Jabbing adjoining cells with a let...

Example 1: The Type III secretion system Example 1: The Type III secretion system  Example 2: The Type VI secretion system The Type VI Secretion System is akin to a “stabbing devic Jabbing adjoining cells with a lethal toxin. It is assembled inside the bacterium’s cytoplasm on the membrane and is primed to act as a spring-loaded “javelin” that shoots out into the target cell. Once fired it is then disassembled and the component protein subunits recycled into another functional unit. It was first discovered as a mechanism bacteria can use to compete with other bacteria. It is now known that they can use it for injecting toxins into host cells during infection. https://www.youtube.com/watch?v https://www.mgc.ac.cn/ =Xk7rxv6HtKo dbVgrG/ le 3: The Photorhabdus Virulence Cassette Nanosyringes (PVC The PVCs are multi-protein molecular machines that act like a nano-scale hypodermic syringes. The bacterium synthesizes these nanosyringes, loaded with a protein toxin, release them from the cell where they seek out a target host cell and inject the toxin. They have specificity binding fibers which allow precise targeting. Genetically related to the T6SS but as they are released, they require no cell-to-cell contact, and of course cannot be recycled. le: The Photorhabdus Virulence Cassette Nanosyringes (PVCs They are made by 16 gene operons and can load any number of different toxin proteins. Different variants are evolved to target different host/cell types. My company “NanoSyrinx” is currently in the process of adapting these as novel pharmaceutical treatments for cancer https://www.mgc.ac.cn/ dbeCIS/ How do pathogens achieve all this?  General strategies: Dealing with phagocytosis agocytosis is one of the central mechanisms in immunity. s performed by several lymphocyte cell types including Neutrophils, Macrophages, Dendritic cells. cterial pathogens can either evade recognition or use strategies to deal with the process. General strategies: Dealing with phagocytosis https://youtu.be /438EovW4tzs 1 2 4 3 5 6 (filamentation) Bacillus cereus vs Phagocyte Examples of evasion or coping strategies General strategies: communication interference Some bacteria can “spy” by binding host cytokines and then modify their behavior appropriately Many bacteria suppress cytokine synthesis – essentially “cutting off” the lines of communication Thank you for listening