Screening for Type III Secretion System Inhibitors

Screening for Type III Secretion System Inhibitors

Commonly used antibiotics are becoming less effective because they target bacterial cell walls or processes, which create a selective pressure for bacteria to become resistant, leading to the formation of “super bugs”. Some of these pathogenic bacteria include E. coli, Salmonella, Chlamydia and Yersinia. These species utilize a type III secretion system (T3SS), which are needle-like structures on their surface used to inject host cells with toxins in order to evade our immune system and cause infection. Recently a new method for testing compounds to determine if they inhibit the Y. pestis T3SS was developed by our lab. This method uses a special growth medium called Magnesium Oxalate (MOX) agar, which produces distinct growth characteristics based on the bacteria's ability, or inability, to secrete toxins. Serial dilution plating was used isolate soil bacteria and each isolate was be patched onto MOX agar plates pre-inoculated with Y. pestis. The areas around each soil isolate were analyzed for the Y. pestisgrowth characteristics associated with blocked T3S. The soil bacteria that exhibited positive results were identified using 16S rDNA sequencing. The goal of this research is to use this method to screen for antimicrobials produced by soil bacteria that may target T3SSs. Many species of bacteria found in soil produce antimicrobials in order to compete with each other for nutrients and space. Using antimicrobials to target the virulence factors in bacteria, instead of cell processes, will reduce the pressure to mutate and adapt while still inhibiting their ability to cause infection.