Submitted to: International Association for Food Protection Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/12/2005
Publication Date: 7/21/2005
Citation: Oscar, T.P., Dulal, K., Boucaud, D. 2005. Fitness problems in Escherichia coli k-12 transformed with a high copy plasmid encoding the green fluorescent protein. International Association for Food Protection. Abstract. P2-08. p. 87.
Technical Abstract: The green fluorescent protein (GFP) of the jellyfish Aequorea victoria has been widely used as a biomarker in eucaryotic and prokaryotic cells and has potential for developing predictive models for behavior of single strains of bacteria in naturally contaminated food and environmental systems. However, constitutive production of GFP in bacteria can result in reduced fitness in the form of slower growth. Consequently, a high copy plasmid with gfp under the control of a tetracycline inducible promoter (pTIPgfp) was introduced into Escherichia coli K-12. To validate the GFP strain of E. coli K-12 for predictive modeling studies, growth kinetics of the parent and GFP strain were compared at 10, 25 and 40 C on sterilized cooked chicken breast meat (sterilized chicken). Although gfp expression was not induced during growth on sterilized chicken, maximum specific growth rate (umax) of the GFP strain was reduced (P < 0.05), regardless of incubation temperature. When growth kinetics were compared in BHI broth at 40 C, umax and maximum population density were reduced (P < 0.05) to the same extent in the absence and presence of tetracycline. These results indicated that the presence of the high copy plasmid introduced a fitness problem in E. coli K-12 in the form of slower growth and reduced cell yield that was independent of GFP production. Thus, use of a low copy plasmid or insertion of a single copy of gfp into the chromosome may be required to avoid fitness problems in GFP bacteria.