Dissecting Bacteria and Mammalian Cells by Whole-Cell NMR: Cell Walls, Ribosomes, Nuclei, Oh My!

Abstract

Our research program is inspired by the challenge and importance of elucidating chemical structure and function in complex biological systems and introducing new strategies to prevent and treat human disease. We integrate solid-state NMR spectroscopy with biochemical and microbiological methods to determine atomic- and molecular-level detail in macromolecular assemblies, intact cells, and bacterial biofilms. In this presentation, I will present our efforts to quantify and identify differences in bacterial cell wall composition by whole-cell NMR and to characterize the modes of action of antibiotics in intact bacterial cell samples. Traditional biochemical methods have delivered most of the information to date regarding antibiotic modes of action, but can be accompanied by molecular ambiguities. A new mode of action has even been recently ascribed to beta-lactams such as penicillin. Solid-state NMR methods enable a comprehensive analysis of cell-wall and cellular pools of carbon and nitrogen and can be used to measure distances between labeled small molecules and labeled sites in the bacterial cell. We have identified differential spectral signatures to quantify cell-wall parameters and to quantify the balance of peptidoglycan and teichoic acid in the bacterial cell wall, even in the absence of specific isotopic labeling, and have examined inhibitors with alternate modes of action, such as ribosome-targeting antibiotics. Towards a view of what carbon pools make up a cell, I will also compare and contrast compositional pools among bacteria and mammalian cells.