Susan J. Fisher Ph.D.

The Fisher lab's major area of investigation is understanding adherence mechanisms used by microbial pathogens. In one project we are testing the hypothesis that bacteria which colonize the oral cavity do so by interacting with the carbohydrate portions of salivary receptors. In general, we use whole-cell ligand blotting (overlaying blots of salivary glycoproteins with bacteria) to identify interactions between individual salivary molecules and particular bacterial species. This technique led to the identification of a highly glycosylated, proline-rich glycoprotein (PRG) as the major Fusobacterium nucleatum receptor in saliva. We then determined, using mass spectrometry and nuclear magnetic resonance spectroscopy, the complete structure of the subset of PRG oligosaccharides that carry the bacterial receptor activity. We used this same experimental strategy to study the interaction between streptococci and the low-molecular-weight salivary mucin. Very recently we showed that this glycoprotein carries sulfated sialyl Lex structures and is a ligand for L-selectin. This observation has interesting implications for leukocyte trafficking in the oral cavity.