Item – Theses Canada

​
OCLC number
670418853
Link(s) to full text
LAC copy
LAC copy
Author
Harrison, Joe J.(Joe Jonathan),1975-
Title
Multimetal resistance and tolerance in microbial biofilms.
Degree
Ph. D. -- University of Calgary, 2008
Publisher
Ottawa : Library and Archives Canada = Bibliothèque et Archives Canada, [2009]
Description
3 microfiches
Notes
Includes bibliographical references.
Abstract
Geochemical cycling and industrial pollution have made toxic metals a pervasive environmental pressure throughout the world. Growth in a biofilm, which is the attachment and proliferation of microorganisms at a surface, is a strategy which microbes may use to survive a toxic flux in these inorganic compounds. This research has focused on identifying the reasons why biofilms are less susceptible to metal toxicity than freeswimming planktonic microbes. During this research, I have developed a simple, high-throughput technology for metal susceptibility testing, 'in situ' microscopy and three-dimensional visualization of microbial biofilms using the Calgary Biofilm Device. By using this technique, it was possible to perform combinatorial experiments to examine the effects of exposure times, growth conditions and gene deletion on the susceptibility of bacterial and fungal biofilms to arrays of toxic metals and other antimicrobial agents. This approach identified several genetic, cellular and biochemical processes that may contribute to biofilm "multimetal resistance" and "multimetal tolerance." In conjunction with evidence from the literature, I have assembled these processes into a multifactorial model that I have split into seven components based on mechanism: (1) Chemical and metabolic gradation in the biofilm introduced by structured population growth. (2) Cell-cell signaling events (via small "messenger" molecules) that contribute to the biofilm lifestyle. (3) Metal-ion immobilization by adsorption to biomass. (4) Bioinorganic reactions of metal ions with microbial metabolites. (5) Adaptive responses of the biofilm that may change the physiology of some cells to a metal resistant or tolerant state. (6) Metabolically quiescent cells, termed persister cells, which do not grow, yet do not die on exposure to metal ions. (7) Genetic rearrangements or mutations that produce variant phenotypes in the population. My assessment of the available evidence suggests that the reduced susceptibility of biofilms to toxic metals is linked to a natural process of cellular diversification that is ongoing within the microbial population. This model is a conceptual step towards understanding biofilms as a population strategy for microbial survival during exposure to toxic stressors in a diverse range of natural, industrial and clinical settings.
ISBN
9780494443972
0494443979