Salmonella cause typhoid fever and food poisoning. One of the key structural features of the infection process for this bacterium is the "type III secretion system". This enables it to secrete bacterial proteins into the host cell. The central component of this apparatus has a structure akin to that of a hollow needle, whose length is crucial for the success of the infection process.
Dr. Thomas C. Marlovits, scientific head of the new "Vienna Spot of Excellence", together with Yale University professor Jorge E. Galan and other colleagues from the USA, has now explained how the exact length of the needle is determined during the assembly of this biological nano-machine.
Says Dr. Marlovits: "A fine example of molecular multi-tasking, the TTSS is not only responsible for transporting bacterial proteins into the host cell, but also for its own assembly from some 200 individual structural proteins. The length of the needle structure is controlled by a sophisticated mechanism. The core of this mechanism is the change in the specificity of the TTSS for different proteins. Although the TTSS still has a high specificity for its own structural proteins during the initial phase of the assembly process, this specificity changes later to handle the proteins that are important for the actual infection process. A change in the structure of the TTSS is crucial for this transformation."