Current Members

The Pel polysaccharide is a widespread biofilm component involved in chronic infections. It is produced by Gram-negative and Gram-positive bacteria and typically regulated by the second messenger c-di-GMP. Interestingly, Gram-positives contain a subset of species that lack genes required for the c-di-GMP pathway. My project aims to understand the underlying principles of Pel regulation and production in this subset using S. intermedius as model organism with the hope of finding an alternative treatment approach for Pel related infections.

Development of glycoside hydrolases as therapeutics.

Microbial biofilms are involved in many chronic infections. The microbial cells within these biofilms are enclosed in a self-produced polymeric matrix. Using biochemical techniques and cryoelectron microscopy, my work aims to understand at the molecular level the protein machinery that synthesizes exopolysaccharides, a major component of the biofilm matrix, such as Pel complex in S. intermedius, P. aeruginosa and B. cereus or the PgaAB complex that participates in the generation of Poly-β-1,6-N-acetyl-D-glucosamine (PNAG) in E. coli.

My project is on understanding the regulation of an oligomeric complex that spans the cell membrane of the Gram-positive opportunistic pathogen Streptococcus intermedius. This complex is shown to regulate biofilm formation in other Streptococcus species. First, I will identify how this gene, present in an operon, is regulated (i.e. the transcription factors involved). Second, how this complex is involved with the formation of biofilms. Biofilms are a major contributor to persistent infections, so the knowledge gained from this project could ultimately expand our therapeutic options.

A primary factor contributing to the pathogenicity of Streptococcus intermedius is the bacterium’s ability to form a biofilm. Various strains of S. intermedius exhibit two phenotypes of biofilm development: a surface-adherent biofilm or a liquid-suspended aggregated biofilm. The processes underpinning the regulation of biofilm formation in S. intermedius remain largely unknown. My project aims to identify the secondary messenger and proteins responsible for coordinating biofilm formation in S. intermedius. In turn, we hope to examine the phenotypic variation in strains with altered levels of the messenger.

Poly-β-1,6-N-acetyl-D-glucosamine (PNAG) is an exopolysaccharide essential for virulence and biofilm formation in both Gram-positive and Gram-negative bacteria. The polymerization and export of PNAG in gram-negative bacteria, such as E. coli and K. pneumoniae, is linked to a four-gene operon (pgaABCD). My project focuses on understanding the molecular mechanisms involved in the biosynthesis, modification, and export of PNAG by the membrane protein complexes PgaCD and PgaAB.

Bacterial infections often grow as a biofilm, which is an interconnected group of cells surrounded by an extracellular matrix (ECM). The Pel exopolysaccharide is the major contributor to the Pseudomonas aeruginosa ECM. The biosynthesis of Pel is regulated by the binding of c-di-GMP to PelD, a c-di-GMP receptor. We recently discovered that PelD interacts directly with BifA, a phosphodiesterase that breaks down c-di-GMP. My project aims to understand how BifA regulates PelD to influence biofilm formation in P. aeruginosa. In addition to my research, I like to get involved in various extracurricular initiatives. For example, I was the student Communication Officer for GlycoNet for the 2021-2022 term. In this role, I wrote articles that details advice for surviving graduate school and tips for generating scientific posters.

The Pel polysaccharide is a major component of the Pseudomonas aeruginosa biofilm produced by the pelABCDEFG operon, which contributes to its multi-antibiotic resistance. Previous studies have shown that PelA deacetylase activity is crucial for detection of Pel polymer produced by P. aeruginosa, and this activity is enhanced in the presence of the scaffolding protein PelB. My project aims to understand the mechanism of Pel processing and export by the PelAB complex. Using structural biology techniques such as cryo-EM and X-ray crystallography, I will focus on investigating structural changes induced in PelA upon complex formation with PelB, which can give insights on how PelB regulates PelA activity. Understanding the Pel biosynthetic complex mechanistically will allow us to develop targeted therapeutics against P. aeruginosa infections.

The cyclic dynamics of extension, surface adherence, and retraction of the Type IV pili (T4P) are powered largely by cytoplasmic motor ATPases via ATP hydrolysis. Previous studies in the T4aP system demonstrated the existence of multiple ATPases performing exclusive roles in either extension or retraction. Conversely, recent evidence in the Tad (tight adherence) system suggests that a bifunctional ATPase can drive both functions. Hence, my current project utilizes an X-ray crystallographic approach to determine the structure of the Tad pilus ATPase, leveraging C. crescentus as a model. The results will help us understand how structural differences amongst these ATPases ultimately produce varying functions.