Monday, September 22,  12:00 – 1:30 pm, in 489 Minor Hall

Graduate Student Seminar

presented by

Daniel Coates, PhD Candidate (Chung Lab)


Quantifying crowded feature interactions with letter-like symbols
Despite years of study, fundamental issues remain in visual perception: how peripheral vision differs from foveal vision, and how humans recognize simple line figures such as letters of the alphabet. In this talk, I present experiments with artificial letter-like symbols presented in the periphery, where they are strongly affected by crowding, the deleterious influence of flanking shapes on detection of a target. With these controlled stimuli, specific questions are addressed about the interactions of adjacent spatial features in the periphery, putting constraints on models of crowded percepts.


Aaron Sullivan, PhD Candidate (Fleiszig Lab)

Will vaccines directed against the type III secretion system of gram-negative bacteria work?
In order to compete with the rise of antibiotic resistance among bacterial pathogens, new and novel strategies are being developed.  For example, efforts are underway to develop vaccines against type III secretion systems (T3SSs) of gram-negative bacteria. T3SSs allow bacteria to secrete specific toxins directly into host cells, and are thought critical to pathogenesis of disease. Pseudomonas aeruginosa is one such bacterium, capable of causing both sight and life threatening infections, that is highly resistant to currently available antimicrobials. To initiate disease in the cornea, bacteria must first gain access to the stroma that lies underneath the surface epithelial barrier. While the cornea of the eye normally defends itself successfully against P. aeruginosa and other potential pathogens, injury or contact lens wear can predispose it to infection. With these factors in mind we developed methods, in mice, for studying bacterial penetration through the corneal epithelium to explore the role of the P. aeruginosa T3SS. The results showed that it can indeed mediate P. aeruginosa traversal through the susceptible corneal epithelium. Surprisingly, the results also showed that if mice were immunocompromised (MyD88 deficient) the T3SS was no longer required. Moreover, if longer exposure times were used, even immunocompetent mice were susceptible to mutants lacking the T3SS in some strains. In yet another strain of P. aeruginosa (that hypersecretes T3SS effectors) no traversal was found at all. Thus, the T3SS is neither necessary, nor is it sufficient for traversal.  A screen of other virulence factors revealed that LasB (secreted via a type 2 secretion system) could also mediate traversal. Thus, multiple virulence factors/secretion systems can allow bacteria to penetrate protective epithelial barriers, suggesting that vaccines against only one will be effective in only certain circumstances.

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