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Characterization of Gene Expression During Biofilm Development in Mycobacterium smegmatis, and Genetic Analysis of a Surface Translocation-Defective Transposon Mutant

Balachandran, Amrita (2012) Characterization of Gene Expression During Biofilm Development in Mycobacterium smegmatis, and Genetic Analysis of a Surface Translocation-Defective Transposon Mutant. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Tuberculosis is the leading cause of death due to a single infectious agent, and over one-third of the global population is infected with Mycobacterium tuberculosis, the etiologic agent of human tuberculosis. In recent years, the likelihood of biofilm-based infections contributing toward bacterial persistence and increased drug tolerance, has gained some recognition. M. tuberculosis and its non-pathogenic fast-growing relative, M. smegmatis, have been found to form biofilms that harbor bacteria that are more resistant to anti-tuberculosis agents than free-living cells.

Biofilm formation involves the development of several distinct morphological structures, with associated physiological features. Bacteria growing within biofilms exist as heterogeneous populations, dependent on the distinct micro-environments within the complex community structure. Consequently, gene expression profiles differ between sub-populations of cells, and also during distinct stages of biofilm development. Gene expression in biofilms also differs greatly from the gene expression profiles of planktonically growing cells of the same species.

M. smegmatis biofilms can serve as a model for other mycobacterial biofilms. Transcriptome analyses of M. smegmatis biofilms have led to the identification of several genes that were induced in a biofilm-specific pattern.

Iron plays an essential role in mycobacterial growth, metabolism and infection. Taken together with its significance in biofilm development, the detailed profiling of the expression of iron acquisition genes in mature biofilms would provide insight into the physiological state of the bacterial cells within these structures. Using stable fluorescent reporter constructs, we have provided a detailed profile for the expression of the intramembrane-associated siderophore, mycobactin. Our results suggest that mycobactin biosynthesis is differentially induced in biofilms and in liquid cultures. In mature biofilms, a significant proportion of cells induce mycobactin biosynthesis in spite of the availability of iron-rich conditions. Our analyses also attempt to sort out subsets of cells within the biofilm that differentially induce mycobactin biosynthesis.

In a related study undertaken to understand the relationship between biofilm formation and surface translocation in M. smegmatis, we have isolated a transposon mutant that is defective in sliding motility, but proficient in biofilm formation. This mutant suggests that biofilm formation in M. smegmatis does not depend on sliding motility.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Balachandran, Amritaamb92@pitt.eduAMB92
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairHatfull, Grahamgfh@pitt.eduGFH
Committee MemberBrodsky, Jeffreyjbrodsky@pitt.eduJBRODSKY
Committee MemberLawrence, Jeffreyjlawrenc@pitt.eduJLAWRENC
Committee MemberHendrix, Rogerrhx@pitt.eduRHX
Committee MemberNau, Gerardgjnau@pitt.eduGJNAU
Date: 12 June 2012
Date Type: Publication
Defense Date: 19 January 2012
Approval Date: 12 June 2012
Submission Date: 20 April 2012
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Number of Pages: 183
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Biological Sciences
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: biofilms, Mycobacteria, iron, siderophore, mycobactin, surface translocation, sliding motility
Date Deposited: 12 Jun 2012 18:12
Last Modified: 12 Jun 2017 05:15


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