Kerensa McElroy (UNSW) started us off immersing the audience in deep sequencing in order to understand pathogen evolution in biofilms. Two model pathogens, Phaeobacter gallaeciensis and Pseudomonas aeruginosa, were used to grow biofilms under conditions that select for reproducible phenotypic diversification. Variations in the genetic structure were revealed addressing different stages of biofilm development. Kerensa could describe genetic variation accurately and comprehensively within evolving populations using her established approach in genome-wide deep sequencing.
Event Date:Wednesday, November 30, 2011 - 18:15 - 18:30
Institution:University of Sydney
The fungal secretome and virulence: analysis of the proteins secreted by Cryptococcus gattii strains with different virulence profiles.
Cryptococcus gattii is a ubiquitous environmental yeast-like fungus capable of causing disease in a wide range of animal hosts. In humans, disease progression begins after inhalation of the infectious propagule leading to infection of the lung. The infective yeast cells can then disseminate to the central nervous system, resulting in meningoencephalitis, which can be fatal if left untreated.
Closely related strains of C. gattii exhibit significantly different degrees of virulence in the mammalian host. Fungi utilize absorbtive nutrition and produce a range of secreted degrative enzymes, and as these may invoke a host response, the fungal secretome is likely to be very important in modulating the host-pathogen interaction. In this study, we compare the secretomes of two C. gattii strains, one categorized as hypervirulent (R265) and the other exhibiting low-level virulence (R272). C. gattii was grown under conditions designed to be as similar as possible to those encountered in vivo. Secreted proteins were captured from the culture supernatant by re-circulating across ProteominerTM beads using a closed peristaltic pump system. Concentrated protein was analysed via 1D nanoLC-MS/MS. A total of 27 proteins were identified with only four protein identifications being shared by both strains. The secretome of R265 primarily included uncharacterized proteins containing catalytic cores with roles in carbohydrate degradation as well as the antioxidant superoxide dismutase and a GTPase. R272 secreted a more diverse set of proteins including enolase and transaldolase, enzymes canonically involved in glycolysis and the pentose phosphate pathway respectively, but both also described as fungal allergens that bind IgE.
This work indicates that very different cohorts of proteins are secreted by closely related strains of C. gattii exhibiting different levels of virulence. By enhancing our understanding of the fungal secretome and unraveling these differences it may suggest novel therapeutic strategies or help devise diagnostic markers predicting for disease progression.