On the Gram-positive bacterial cell wall.



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Cell wall is the outermost part of Gram-positive bacteria. It is intricately tied to the bacteria’s response to environmental stimuli and challenges, and its makeup dynamically changes as a part of bacterial adaptation. Peptidoglycan is the biopolymer that composes nearly half of the cell wall, and by studying peptidoglycan valuable insights can be gained into the structure and function of the cell wall. This dissertation examines the chemical compositional changes to the cell wall peptidoglycan in Gram-positive bacteria Enterococcus faecalis and Staphylococcus aureus through solid-state NMR and liquid chromatography-mass spectrometry. These methods analyzed the peptidoglycan without harsh chemical treatments commonly applied to the cell wall that facilitate the use of traditional biochemical methods. Bypassing these treatments allowed for studying various modifications that would have been previously overlooked, and the studies in this dissertation provide peptidoglycan composition analysis at the level of detail where growth conditions and antibiotic challenges to the bacteria could be observed. These studies have revealed that bacteria’s peptidoglycan composition is dynamic, with the bacteria readily altering its cell wall through peptidoglycan as responses to different stimuli and situations. This dissertation presents a representative sampling of experiments undertaken to study the cell wall of Gram-positive bacteria, and it is hoped that they represent different ways of analyzing the cell wall of these medically important pathogens.