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Document Type

Open Access

Degree Program

Food Science

Degree Type

Master of Science (M.S.)

Year Degree Awarded

2012

Month Degree Awarded

February

Keywords

curcumin, biofilm, Listeria monocytogenes, 2D-GE

Abstract

The food-borne pathogen Listeria monocytogenes can attach to the environmental surfaces and develop biofilm which can cause food contamination in the food industries. Sortase A and surface proteins are involved in biofilm and virulence of L. monocytogenes. Curcumin was reported to inhibit sortase A and biofilm in gram positive bacteria. The overall objective of this study was to observe the effect of curcumin (Curcuma longa) on the biofilm formation and surface proteins of L. monocytogenes.

The antibiofilm effect of curcumin against the strain LM21 (wild type) and s22-11G (sortase A defective mutant) was studied using the microtiter plate assay. No significant differences between the growth of the wild type and the sortase A defective mutant were observed at sub-inhibitory concentrations of curcumin. However, a greater biofilm reduction was observed in the strain s22-11G. The effect of curcumin from two different manufacturers on the wild type was also compared by the microtiter plate assay. Both curcumin did not exhibit statistically different effect on the growth of the wild type. However, a greater biofilm inhibitory effect was observed in one curcumin. The HPLC results suggested that curcumin with the greater antibiofilm activity contained higher amount of curcumin which was reported to be the most potent curcuminoid compound in curcumin.

Three different protein extraction methods were evaluated and the most efficient method was used for 2D-GE. When cells were grown in the presence of curcumin, 5 proteins, 16 proteins and 4 proteins were up-regulated, down-regulated and absent, respectively in L. monocytogenes LM21. The influence of the enzyme sortase A upon surface protein expression was evaluated by comparing proteins expressed by wildtype L. monocytogenes LM21 to that of the sortase A mutant, s22-11G. In strain s22-11G, 2 proteins, 8 proteins and 3 proteins were up-regulated, down-regulated and absent in comparison to wildype LM21. The exact information of these differentially expressed proteins still need to be identified by mass spectrometry.

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Advisor(s) or Committee Chair

McLandsborough, Lynne A.