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Characterization of the role of Bacillithiol in Staphylococcus aureus / by Ana Catalina Posada.

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Author	Posada, Ana Catalina.
Title	Characterization of the role of Bacillithiol in Staphylococcus aureus / by Ana Catalina Posada.
Date	2013
Abstract	As methicillin-resistant Staphylococcus aureus (MRSA) hospitalizations keep increasing, the understanding of the characteristics that make one isolate more successful over another is paramount. Strain variations among Staphylococcus aureus observed clinically and experimentally can often be attributed to disparate expression of a variety of cellular factors. This study was undertaken to identify genes or gene products that function apart from methicillin-resistance but still affect the expression of mecA, a gene encoding the methicillin resistance element PBP2A. The mutation of six genes (acuAC, fosB, gltC, sa2163, and sa1428) that were identified in our screen resulted in a decrease in mecA expression as measured by GFP reporter construct. These changes in mecA expression in the mutants, however, do not appear to affect the bacteria's resistance to cell-wall active antibiotics other than fosfomycin. Here we show that the absence of FosB, a fosfomycin resistance gene, led to an increase in mecA expression as compared to the parent. FosB uses bacillithiol (BSH), a recently-discovered low molecular weight thiol, as a substrate to inactivate fosfomycin. Mutants of fosB and bshA (the first gene in the BSH biosynthetic pathway) were made in several MRSA strains to further characterize the role of BSH in the physiology of S. aureus. Our data implicate both FosB and BSH in the oxidative stress response as the fosB and bshA mutants are sensitive to oxidative stress generated by hydrogen peroxide. The observations that the fosB and bshA mutants have decreased intracellular levels of the reductants BSH, cysteine, CoASH, and NADPH as well as a lower antioxidant capacity relative to their isogenic parents suggest a linkage between the reductants and the cell's ability to maintain its reducing capacity. However, the absence of BSH impairs the ability of a strain to survive in a whole blood assay. The data presented here argue that a better understanding of the role of the BSH redox system in the physiology of S. aureus will
Description	xii, 205 leaves : ill. 28 cm.
Format	application/pdf
Advisor	David Bzik, Ambrose Cheung, Mary Lou Guerinot, John Helmann
College	Dartmouth Medical School. Department of Microbiology and Immunology.
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D.)--Dartmouth College.
Copyright	All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means without permission in writing from the author.
DOI	http://dx.doi.org/10.1349/ddlp.1002

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