Comparison of Predictive Models for Growth of Parent and Green Fluorescent Protein–Producing Strains of Salmonella

Abstract

The green fluorescent protein (GFP) from the jellyfish Aequorea victoria can be expressed in, and used to follow the fate of, Salmonella in microbiologically complex ecosystems such as food. As a first step in the evaluation of GFP as a tool for the development of predictive models for naturally contaminated food, the present study was undertaken to compare the growth kinetics of parent and GFP-producing strains of Salmonella. A previously established sterile chicken burger model system was used to compare the growth kinetics of stationary-phase cells of parent and GFP strains of Salmonella Enteritidis, Salmonella Typhimurium, and Salmonella Dublin. Growth curves for constant temperatures from 10 to 48 degrees C were fit to a two- or three-phase linear model to determine lag time, specific growth rate, and maximum population density. Secondary models for the growth parameters as a function of temperature were generated and compared between the parent and GFP strain pairs. The effects of GFP on the three growth parameters were significant and were affected by serotype and incubation temperature. The expression of GFP reduced specific growth rate and maximum population density while having only a small effect on the lag times of the three serotypes. The results of this study indicate that the growth kinetics of the GFP strains tested were different from those of the parent strains and thus would not be good marker strains for the development of predictive models for naturally contaminated food.

Development and validation of a neural network model for predicting growth of Salmonella Newport on diced Roma tomatoes during simulated salad preparation and serving: extrapolation to other serotypes

“…Three serotypes had growth on diced Roma tomatoes that was different from that of Salmonella Newport. The finding that growth among serotypes of Salmonella is mostly similar but on occasion differs is consistent with previous studies conducted in laboratory broth (Oscar, 1998), on cooked chicken without native microflora (Oscar, 2000(Oscar, , 2003, and on ground chicken with native microflora (Oscar, 2009(Oscar, , 2015.…”

Development of a whole cell green fluorescent sensor for lysine quantification

“…Taking this into account as well as the previous reports on cell toxicity of GFP E. coli O157:H7 (Fratamico et al 1997), Trichoderma harzianum (Bae and Knudsen 2000) and Salmonella spp. (Oscar 2003), it was important to determine the growth rate of the strain under the conditions of expressed and non-expressed gfpmut3 and compare this to the growth rate of the parental strain. No significant differences in growth rates were observed (Table 2).…”

Autofluorescence and green fluorescent protein-derived fluorescence in Listeria innocua

“…Oscar et al [37] reported a 50 min lag phase extension of a Salmonella transformed strain which however, was not found significant. Oscar [38] also observed that constitutive expression of gfp altered growth characteristics of transformed Salmonella as the changes affected more growth rates and maximum population densities than lag times. In our study, however, L. innocua M1 transformation and gfp expression did not alter the growth rate which agreed with the reports of [39][40][41] for gfp-labeled Bordetella pertussis, Lactococcus lactis and E. coli K-12 strains respectively.…”