Decoding cell surface chemistry and function in Staphylococcus aureus

Stanford University, Stanford CA

Investigators

Abstract

PROJECT SUMMARY Bacteria are essential to human health and also one of our greatest threats. Bacteria in the microbiome facilitate gut health and prevent proliferation of unwanted organisms. However, pathogenic bacteria damage tissues and enmesh themselves in communities termed biofilms that evade antimicrobials and host defenses. The unique chemistries at the bacterial cell surface and the biomolecules and polymers displayed and released by bacteria influence how they engage with their surroundings and underlie the difference between friend and foe in human health and disease. Staphylococcus aureus is a major Gram-positive organism commonly residing harmlessly on the skin and in nasal passages and is a hallmark model organism used to study cell walls and antibiotic modes of action, yet also emerges as a devastating pathogen in difficult-to-treat and antibiotic-resistant infections. This MIRA research program involves three bold and synergistic projects to tackle outstanding molecular questions and decode S. aureus chemistry that distinguishes friend from foe, that underlies biofilm formation and sensitivity to antibiotics, and that influences interactions with other cells and the host. We will implement and expand the unconventional and uniquely enabling cross-disciplinary experimental platform, expertise, and instrumentation we have developed in our laboratory over the last 16 years to illuminate and quantify crucial molecules, bonds, and chemical modifications that have been implicated in virulence and antimicrobial resistance, yet are in molecular blind spots for conventional approaches. In prior work with common E. coli biofilms, our unique approach uncovered a chemical structure never before observed in nature that underlies biofilm function and evaded detection for decades - a chemically modified form of cellulose. In one thrust of this MIRA, we will integrate whole-cell NMR with biochemistry and microscopy to generate blueprints for peptidoglycan and teichoic acid polymer changes as S. aureus stealthily reprograms cell walls in biofilms and persister cells, including teichoic modifications implicated in virulence. We seek to establish likely relationships with antibiotic efficacy and resistance, including consideration of vancomycin conjugates we designed to interact with cell-surface anions that exhibit extraordinary activity in eradicating biofilm bacteria. In the second area, we will introduce labeling and spectroscopic detection methods and detect atomic-level contacts between whole-cell teichoic acids and proteins and peptides speculated to engage with teichoic acids. In the third area, we will define biofilm extracellular matrix composition among S. aureus to understand how they build multicellular architectures, using our powerfully integrated biochemistry, proteomics, transcriptomics, microscopy, and solid-state NMR approach. This MIRA program will yield fundamental and translationally relevant discoveries and introduce broadly applicable strategies as many important cell-surface functions are achieved by polysaccharides, glycoconjugates, and heterogeneous, insoluble assemblies.