MicroSocial Seminar Series: Saúl J. Flores

Speaker: Saúl J. Flores, Ph.D. candidate in biochemistry

 Talk Title: Mechanistic and Structural Characterization of the Nfr Exopolysaccharide Pathway in Escherichia coli

Abstract: Bacterial biofilms are structured microbial communities embedded in an extracellular polymeric substance (EPS) matrix that promotes persistence in clinical, industrial, and environmental settings. Polysaccharides are major structural components of this matrix, yet the molecular basis of their synthesis and remodeling remains poorly defined. This project investigates how the Nfr exopolysaccharide pathway in Escherichia coli produces and remodels a poly-N-acetylmannosamine (ManNAc)-containing polymer, with the goal of linking molecular function to emergent biofilm phenotypes.

This work focuses on the membrane glycosyltransferase NfrB and the putative glycosyl hydrolase YbcH using complementary biochemical, structural, and computational approaches. NfrB has been isolated and reconstituted through a detergent-free workflow based on amphipathic copolymer screening, yielding native-like synthetic nanodiscs suitable for functional assays and single-particle cryogenic electron microscopy. Iterative grid optimization has improved particle quality and 2D class averages, supporting ongoing structural studies. Enzymatic activity is being evaluated using UDP-release assays to probe substrate utilization and cyclic di-GMP-dependent regulation. In parallel, docking of defined ManNAc oligomers and molecular dynamics simulations are being used to identify candidate binding and catalytic residues in YbcH for targeted mutagenesis.

Engineered strains expressing the Nfr system show distinct extracellular matrix material and altered biofilm architecture, indicating that this pathway shapes higher-order community behavior. Together, these results establish a foundation for determining how this polymer is produced and remodeled, while informing the development of molecular probes for studying native-like biofilms and new strategies for anti-biofilm engineering.

About the event: The MicroSocial Seminar Series aims to facilitate scientific exchange and community building across the University of Maryland's microbiome research community. Monthly seminars feature UMD speakers, including students and faculty, who give short research presentations (either 2 x 12 minutes or 1 x 20 minute talks) followed by a social happy 1/2 hour over coffee and snacks. We welcome presentations about in-progress work or recent results, with the goal to provide an overview, receive feedback, promote opportunities for collaboration, or identify community interests and needs that the center may address. Open to all of UMD, the monthly seminar takes place on Tuesdays from 3:30–4:30 p.m.