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The Contribution of One-carbon Metabolism to the Pathogenesis of Francisella tularensis

Brown, Matthew J (2013) The Contribution of One-carbon Metabolism to the Pathogenesis of Francisella tularensis. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Abstract

An emerging paradigm shift in bacterial pathogenesis has resulted in renewed interest in metabolism during infection. The acquisition and synthesis of metabolites by pathogens in the host represents a critical obstacle to successful colonization and infection. The value of bacterial metabolic pathways during infection remains poorly characterized for many pathogens and warrants further investigation. One aspect of this, the contribution of one-carbon metabolism to pathogenic fitness was assessed. This metabolic pathway primarily transfers single carbons and contributes to the synthesis of amino acids, DNA, and proteins. The donated carbon is typically derived from 5,10-methylenetetrahydrofolate, a central compound in one-carbon metabolism. Since the requirement of a metabolic pathway may vary among nutritionally diverse sites within a host, a systemic infection involving multiple niches would be an ideal model to assess the contribution of these pathways. Francisella tularensis is a gram-negative bacterium, a tier one bioterrorism agent, and the causative agent of a debilitating febrile illness known as tularemia. Since this organism is capable of establishing a systemic infection throughout the host, it provides an excellent opportunity to evaluate bacterial metabolism during infection. To evaluate this system in F. tularensis, mutagenesis of the two known sources of 5,10-methylenetetrahydrofolate, the glycine cleavage system and the serine hydroxymethyltransferase, was performed. Loss of either of these pathways resulted in serine auxotrophy, identifying one-carbon metabolism as the exclusive serine biosynthetic pathway of F. tularensis. Under standard assay conditions, neither the glycine cleavage system nor the serine hydroxymethyltransferase proved to be essential for intracellular replication in the virulent F. tularensis subsp. tularensis. Despite this result, both 5,10-methylenetetrahydrofolate producing pathways contributed to pathogenesis in a murine model of pneumonic tularemia. Further, these pathways contributed to pathogenic fitness of Francisella to varying degrees throughout the host. Critically, a significant reduction in bacteremia was associated with the loss of either system. These studies highlight differing nutritional environments of distinct sites in the host and confirm that these sites exert variable metabolic stresses on this invasive pathogen. This work identifies one-carbon metabolism as a key bacterial metabolic pathway employed by F. tularensis to overcome nutritional limitation during infection.


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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Brown, Matthew Jmjb154@pitt.eduMJB154
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Thesis AdvisorNau, Gerard Jgjnau@pitt.eduGJNAU
Committee MemberMcClane, Bruce Abamcc@pitt.eduBAMCC
Committee MemberKhan, Saleem Akhan@pitt.eduKHAN
Committee MemberCoyne, Carolyn Bcoynec2@pitt.eduCOYNEC2
Committee MemberShanks, Robert M Qshanksrm@upmc.eduRMS68
Date: 20 November 2013
Date Type: Publication
Defense Date: 5 November 2013
Approval Date: 20 November 2013
Submission Date: 19 November 2013
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Number of Pages: 167
Institution: University of Pittsburgh
Schools and Programs: School of Medicine > Molecular Virology and Microbiology
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Francisella tularensis, Tularemia, Glycine Cleavage System, Serine Hydroxymethyltransferase, One-carbon Metabolism
Date Deposited: 20 Nov 2013 13:58
Last Modified: 19 Dec 2016 14:41
URI: http://d-scholarship.pitt.edu/id/eprint/20028

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