Talia Richter-Sissman

Staphylococcus Aureus bacteria can cause serious infection in humans upon access to deeper tissue. Toxins like LukAB play a large role in the development of the infection as these toxins harm human immune cells. It was previously found that autolysin, a cell wall hydrolase, contributes to whether LukAB is moved, or sorted, from inside the cell, where the toxin cannot harm immune cells, to outside the cell, where it can. A cell wall hydrolase is an enzyme that breaks down the peptidoglycan layer of the cell wall, contributing to the natural turn over process of the cell. The goal of this research was to understand how autolysin affects the sorting of LukAB.  Researchers used mutants of the wild type S. Aureus bacteria that did not produce autolysin and quantified the amount of LukAB that was inside the cell compared to the amount that was secreted from the cell. The results show that autolysin helps control the sorting of LukAB, as the samples that contained the mutant without autolysin had more LukAB sorted to outside the cell and the wild type had more LukAB inside the cell. The increased sorting of LukAB to outside of the cell in the mutants created more harm to human immune cells. Mechanically, this difference in LukAB sorting was caused by the autolysin creating holes in the peptidoglycan layer of the cell wall, which traps the LukAB. Therefore, these toxins cannot be sorted to outside of the cell and cannot harm immune cells. Overall, this research revealed that the cell wall hydrolase activity of Atl contributes to whether toxins are secreted from S. Aureus cells, and helps contribute to an understanding of how bacteria transport proteins across the cell wall.