Molecular mechanisms of encystation and sporulation. (360G-Wellcome-100293_Z_12_Z)

Most protozoa survive environmental stress by encapsulating to form a cyst or spore. This process is medically important for pathogenic protists since cysts are resistant to immune clearance, antibiotics and biocides. Cysts of bacterivorous protists such as Acanthamoeba additionally act as vectors for airborne dispersal of bacterial pathogens, such as Legionella pneumoniae, Vibrio cholerae and MRSA. Due to the limited genetic tractibility of encysting organisms, the mechanisms controlling encyst ation are largely unknown. Dictyostelid social amoebas survive stress by building fruiting structures with encapsulated spores and stalk cells. Both cell types mature in response to PKA activation, and we showed that this process is derived from encystation in solitary amoebas, which we found to also require cAMP acting on PKA. The encysting Dictyostelid Polysphondylium pallidum is uniquely suitable for both reverse and forward genetic approaches, allowing us to identify several encystation gene s, which proved to be deeply conserved in protozoa. This included one suitable target for anti-encystation drug development, which we are currently exploring in collaboration with the Dundee Drug Discovery Unit. In our future research we will combine the power of genetics with proteomics and drug development to achieve the following goals: Find all genes that control encystation in P.pallidum and the order in which they interact. Investigate functional conservation of essential genes in path ogenic protists and instigate compound screens to find inhibitors. Identify missing links in the pathways that regulate spore and stalk cell encapsulation in Dictyostelia and establish how these pathways emerged from the ancestral encystation pathway.