Polymyxin B as a Tool to Study Gram-Negative Bacterial Phenotypes

Abstract

The study of Gram-negative bacteria is important for developing an understanding of both bacterial physiology and to develop new drugs to treat Gram-negative bacterial infections. One unique aspect of Gram-negative bacteria is the outer membrane, which is an asymmetric membrane composed of lipopolysaccharide (LPS) in the outer leaflet. This dissertation develops new fluorescent tools based on the antibiotic polymyxin B and applies it to studies of LPS biogenesis in whole cells. The development of these tools enables a novel understanding of LPS localization in whole cells, which was not previously possible with established analytical methods. Through a more detailed understanding of perturbations to LPS localization, we have been able to more specifically elucidate the impact on LPS biogenesis by both new and established antimicrobial compounds. We have also used a fluorescent polymyxin B derivative to also enable an appreciation of antibiotic hypersensitivity and tolerance that is difficult to normally isolate within a population, and which indicates a regulatory link between outer membrane and cell wall biogenesis.