Clostridium difficile Responds to Antimicrobial Peptides and Oxidative Stress

Persistent Link:
http://hdl.handle.net/10150/578613
Title:
Clostridium difficile Responds to Antimicrobial Peptides and Oxidative Stress
Author:
McQuade, Rebecca
Issue Date:
2015
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Embargo:
Release December 9, 2016
Abstract:
Clostridium difficile (CD) is the leading cause of bacterial hospital-associated infection in North America. How CD colonizes the human host, including its response to the innate immune system and other stresses, is poorly understood. This work considers CD's defenses against two stresses found in the host - the antimicrobial peptide LL-37 and reactive oxygen species (ROS). LL-37 had bactericidal activity against CD. CD strains varied in their sensitivity to the peptide, and epidemic-associated strains were more resistant to LL-37 than others. CD became more resistant to LL-37 following exposure to sub-lethal concentrations of the peptide, suggesting the presence of inducible resistance mechanisms. A quantitative proteomics analysis revealed definite alterations in CD protein expression caused by LL-37. Specific changes included increased expression of DltB, a protein previously reported to confer resistance against other antimicrobial peptides. Notably, disruption of individual LL-37-induced genes did not sensitize CD to the peptide. This suggests functional redundancy, and that LL-37 may cause global changes in protein expression, not limited to antimicrobial peptide resistance determinants. One of the proteins most strongly induced by LL-37 was a predicted superoxide reductase (SOR). As CD is considered a strict anaerobe, expression of a predicted antioxidant protein was an interesting finding. Heterologous expression of CD SOR in a superoxide dismutase-deficient E. coli strain confirmed its action as a superoxide scavenger. Insertional inactivation of SOR rendered CD more sensitive to oxygen and ROS-generating compounds, indicating that SOR contributes to antioxidant defense in CD. SOR mutants were impaired in their ability to cause disease in hamsters, indicating a role for this protein in infection.
Type:
text; Electronic Dissertation
Keywords:
cathelicidin; Clostridium difficile; LL-37; reactive oxygen species; superoxide reductase; Microbiology; anaerobe
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Microbiology
Degree Grantor:
University of Arizona
Advisor:
Viswanathan, V.K.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen
dc.titleClostridium difficile Responds to Antimicrobial Peptides and Oxidative Stressen_US
dc.creatorMcQuade, Rebeccaen
dc.contributor.authorMcQuade, Rebeccaen
dc.date.issued2015en
dc.publisherThe University of Arizona.en
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en
dc.description.releaseRelease December 9, 2016en
dc.description.abstractClostridium difficile (CD) is the leading cause of bacterial hospital-associated infection in North America. How CD colonizes the human host, including its response to the innate immune system and other stresses, is poorly understood. This work considers CD's defenses against two stresses found in the host - the antimicrobial peptide LL-37 and reactive oxygen species (ROS). LL-37 had bactericidal activity against CD. CD strains varied in their sensitivity to the peptide, and epidemic-associated strains were more resistant to LL-37 than others. CD became more resistant to LL-37 following exposure to sub-lethal concentrations of the peptide, suggesting the presence of inducible resistance mechanisms. A quantitative proteomics analysis revealed definite alterations in CD protein expression caused by LL-37. Specific changes included increased expression of DltB, a protein previously reported to confer resistance against other antimicrobial peptides. Notably, disruption of individual LL-37-induced genes did not sensitize CD to the peptide. This suggests functional redundancy, and that LL-37 may cause global changes in protein expression, not limited to antimicrobial peptide resistance determinants. One of the proteins most strongly induced by LL-37 was a predicted superoxide reductase (SOR). As CD is considered a strict anaerobe, expression of a predicted antioxidant protein was an interesting finding. Heterologous expression of CD SOR in a superoxide dismutase-deficient E. coli strain confirmed its action as a superoxide scavenger. Insertional inactivation of SOR rendered CD more sensitive to oxygen and ROS-generating compounds, indicating that SOR contributes to antioxidant defense in CD. SOR mutants were impaired in their ability to cause disease in hamsters, indicating a role for this protein in infection.en
dc.typetexten
dc.typeElectronic Dissertationen
dc.subjectcathelicidinen
dc.subjectClostridium difficileen
dc.subjectLL-37en
dc.subjectreactive oxygen speciesen
dc.subjectsuperoxide reductaseen
dc.subjectMicrobiologyen
dc.subjectanaerobeen
thesis.degree.namePh.D.en
thesis.degree.leveldoctoralen
thesis.degree.disciplineGraduate Collegeen
thesis.degree.disciplineMicrobiologyen
thesis.degree.grantorUniversity of Arizonaen
dc.contributor.advisorViswanathan, V.K.en
dc.contributor.committeememberViswanathan, V.K.en
dc.contributor.committeememberMolnar, Istvanen
dc.contributor.committeememberSo, Maggieen
dc.contributor.committeememberSterling, Charlesen
dc.contributor.committeememberVedantam, Gayatrien
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