Investigating Gram-positive Wall Teichoic Acid Investigating the Dispensability of Wall Teichoic Acid in the Gram-positive Bacteria Bacillus Subtilis and Staphylococcus Aureus

In recent decades, the emergence of multi-drug resistant pathogenic organisms has proven to be a significant threat to human health. Today, resistant organisms have been identified for every class of antibiotics introduced into clinical practice. Combining this with the knowledge that the introduction of new antimicrobial classes has been almost non-existent since the early 1960's, stresses the importance for new chemical scaffolds and novel therapeutic targets to combat this growing crisis. This thesis focuses on one potential target in Gram-positive bacteria, the biosynthesis of wall teichoic acid polymers. In particular, this study centers on investigating the dispensability of these polymers in both Bacillus subtilis and Staphylococcus aureus, highlighting the utility of these biosynthetic enzymes as novel therapeutic targets. Despite significant examination of teichoic acid gene dispensability in the model organism, B. subtilis, the complexity surrounding gene dispensability was not appreciated until this study. Studying both B. subtilis and S. aureus, a peculiar gene dispensability pattern was uncovered in which early acting enzymes; those responsible for disaccharide synthesis, were dispensable for cell viability, yet the remaining late-acting enzymes remained essential. This paradox was reconciled by demonstrating that the lethality associated with the deletion of late-acting genes could be suppressed by deletion of the early genes. Notwithstanding the ability to survive devoid of wall teichoic acid, these polymers remain an absolute requirement for pathogen virulence. The discoveries presented here have provided remarkable insight into understanding of wall teichoic acid gene dispensability and the complexity associated with this pathway. Furthermore, the ability to generate bacterial strains devoid of wall teichoic acid in both B. subtilis and S. aureus will provide tremendous utility for uncovering a function for this important cell wall component.