Off-campus UMass Amherst users: To download campus access dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.
Non-UMass Amherst users: Please talk to your librarian about requesting this dissertation through interlibrary loan.
Dissertations that have an embargo placed on them will not be available to anyone until the embargo expires.
Open Access Thesis
Master of Science (M.S.)
Year Degree Awarded
Month Degree Awarded
Dispersion is a natural part of a biofilm life cycle in many bacterial species. Dispersion occurs when bacteria revert from a stationary, sessile state to a free-swimming, planktonic state and are freed from a biofilm. Bacterial biofilms consist of proteins, polysaccharides, and extracellular DNA that together make up the extracellular polymeric substances. Surrounded by this mucus-like substance, sessile cells can be extremely difficult to eradicate as compared to the planktonic form of Listeria monocytogenes. Biofilms are robust due to increased surface adherence, inhibition of diffusion of harmful compounds, and increased genetic diversity that exists within a biofilm. As a result, traditional biofilm removal methods are often inadequate; and a novel method for the eradication of Listeria monocytogenes biofilms is needed. Here it is shown that two known biofilm dispersal agents, nitric oxide and cis-2-Decenoic acid, do not induce dispersion in Listeria monocytogenes strain LM23. Nitric oxide and cis-2-Decenoic acid do not influence planktonic cell numbers or biofilm biomass. Ten carbohydrates were screened for their influence on biofilm biomass for use in investigation into natural biofilm dispersion in Listeria monocytogenes strain LM23. Carbohydrate source can significantly increase or decrease biofilm biomass as compared to glucose. Natural biofilm dispersion in Listeria monocytogenes remains inconclusive, yet warrants further investigation. Changes in planktonic cells numbers, sessile cell numbers, and biofilm biomass were tracked under static growth conditions, and suggested a possible dispersion event. However, treatment of biofilms with spent media and observation using scanning electron microscopy did not clarify the results obtained. This research deems the nitric oxide donors, molsidomine (N- (ethoxycarbonyl)-3-(4-morpholinyl)-sydnone imine) and MAHMA NONOate (6-(2-Hydroxy-1-methyl-2-nitrosohydrazino)-N-methyl-1-hexanamine), as well as cis-2-Decenoic acid as ineffective in inducing biofilm dispersion. It also brings about new research questions into natural biofilm dispersion in Listeria monocytogenes.
Lynne A. McLandsborough
Boulden, Brett, "Investigating Natural and Induced Biofilm Dispersion in Listeria monocytogenes" (2017). Masters Theses. 566.