Semester

Spring

Date of Graduation

2008

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Horticulture

Committee Chair

Gary Bissonnette.

Abstract

The BIOLOG microplate system was originally evaluated by Miller and Rhoden (1991) for its ability to correctly identify clinical and environmental isolates. The system determines identity based on the exchange of electrons produced during utilization of a carbon substrate and subsequent respiration, leading to the reduction of a tetrazolium-based color change. Enteric bacteria ( Escherichia coli, Enterobacter sakazakii, and Salmonella enterica serovar Typhimurium) were exposed to heat stress (52°C) and samples were removed as a function of time (0, 15, 30 and 90 min). Stressed cells were monitored with traditional viable cell counts and inoculated into BIOLOG GN plates. The stress response of enteric bacteria results in both physical changes, as reflected by their D-values and sublethal injury, and metabolic changes, as reflected by differential utilization of carbon substrates. Results indicate that the BIOLOG system may be used as a tool to monitor the physiological change of heat-stressed enteric bacteria. The BIOLOG system allows for three types of analysis of the metabolic changes taking place in heat-stressed enteric bacteria. The first two applications of the BIOLOG system demonstrated a generalized approach using AWCD and guild groupings as a tool to monitor physiological changes of heat-stressed enteric bacteria. The use of AWCD and guild groupings proved to be relatively ineffective in monitoring physiological changes in heat-stressed enteric bacteria. The third application that may be used demonstrate possible specific substrate utilization differences in heat-stressed enteric bacteria. Notable changes in specific substrate utilization were observed in thermally-stressed enteric bacteria with the use of the BIOLOG system.

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