Biofilms are communities of microorganisms attached to a surface or each other. Biofilm associated cells are the etiologic agents of recurrent Staphylococcus aureus infections. Oxygen is utilized by S. aureus as a terminal electron acceptor (TEA). Infected human tissues are hypoxic or anoxic. S. aureus increases biofilm formation in response to hypoxia, but how this occurs is unknown. This thesis reports that oxygen influences biofilm formation in its capacity as a TEA for cellular respiration. Genetic, physiological, or chemical inhibition of respiratory processes elicited increased biofilm formation. Impaired respiration led to increased cell lysis via divergent regulation of two processes: increased expression of the AtlA murein hydrolase and decreased expression of the AtlA-inhibitory glycopolymers, WTA. The AltA-dependent release of cytosolic DNA contributed to increased biofilm formation. The fibronectin binding protein A, which is known to interact with AtlA, was also found to be involved in fermentative biofilm formation. Further, cell lysis and biofilm formation were governed by the SrrAB and the SaeRS two-component regulatory systems (TCRS). Genetic evidence suggests that SrrAB-dependent biofilm formation occurs in response to the accumulation of reduced menaquinone. SaeRS-dependent biofilm formation also occurred in response to changes in the respiratory status of the cell, via an as yet undefined signal molecule(s). Further, a high cellular titer of phosphorylated SaeR is required for biofilm formation. Epistasis analyses found that SaeRS and SrrAB influence biofilm formation independent of one another, in vitro. SrrAB and SaeRS governed host colonization in vivo, in the context of a mouse model of orthopedic implant-associated biofilm formation. Of these two TCRS, SrrAB is the dominant system driving biofilm formation in vivo. Biofilms impart protection from innate immunity as well as therapeutic agents. Data presented suggest that pre-formed biofilms, established by fermenting S. aureus, can be prompted to detach and disperse upon exposure to a TEA (oxygen or nitrate). Exposure to oxygen (reaeration) results in increased growth but decreased transcription of atlA and decreased release of DNA. Reaeration is also accompanied by increased transcription of sspA which encodes for a protease capable of cleaving AtlA. Biofilm dispersal was blocked in a strain that is incapable of respiration, suggesting changes in cellular respiratory status are being sensed to trigger dispersal. The transcription of atlA and sspA upon reaeration was modulated in a divergent manner by SrrAB. Data presented suggest that SrrAB achieves divergent regulation of atlA, in two separate growth conditions, via the small RNA, rsaE, as an intermediary. In summation, the results presented define the bases for how oxygen dictates the lifestyle choices of S. aureus. The studies also establish the mechanistic and regulatory bases underlying the formation of anaerobic and fermentative biofilms by S. aureus.
Subject (authority = RUETD)
Topic
Microbial Biology
Subject (authority = ETD-LCSH)
Topic
Staphylococcus aureus infections
Subject (authority = ETD-LCSH)
Topic
Biofilms
RelatedItem (type = host)
TitleInfo
Title
Rutgers University Electronic Theses and Dissertations
Identifier (type = RULIB)
ETD
Identifier
ETD_7894
PhysicalDescription
Form (authority = gmd)
electronic resource
InternetMediaType
application/pdf
InternetMediaType
text/xml
Extent
1 online resource (xvii, 170 p. : ill.)
Note (type = degree)
Ph.D.
Note (type = bibliography)
Includes bibliographical references
Note (type = statement of responsibility)
by Ameya Ashutosh Mashruwala
RelatedItem (type = host)
TitleInfo
Title
Graduate School - New Brunswick Electronic Theses and Dissertations
Identifier (type = local)
rucore19991600001
Location
PhysicalLocation (authority = marcorg); (displayLabel = Rutgers, The State University of New Jersey)
Rutgers University. Graduate School - New Brunswick
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Type
License
Name
Author Agreement License
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I hereby grant to the Rutgers University Libraries and to my school the non-exclusive right to archive, reproduce and distribute my thesis or dissertation, in whole or in part, and/or my abstract, in whole or in part, in and from an electronic format, subject to the release date subsequently stipulated in this submittal form and approved by my school. I represent and stipulate that the thesis or dissertation and its abstract are my original work, that they do not infringe or violate any rights of others, and that I make these grants as the sole owner of the rights to my thesis or dissertation and its abstract. I represent that I have obtained written permissions, when necessary, from the owner(s) of each third party copyrighted matter to be included in my thesis or dissertation and will supply copies of such upon request by my school. I acknowledge that RU ETD and my school will not distribute my thesis or dissertation or its abstract if, in their reasonable judgment, they believe all such rights have not been secured. I acknowledge that I retain ownership rights to the copyright of my work. I also retain the right to use all or part of this thesis or dissertation in future works, such as articles or books.