Title

Investigating the cold tolerance and osmotolerance mechanisms in Yersinia enterocolitica

Date of Completion

January 2006

Keywords

Agriculture, Food Science and Technology|Biology, Microbiology

Degree

Ph.D.

Abstract

Y. enterocolitica is a major food safety and public health concern because of its psychrotrophic (ability to grow at cold temperatures) and osmotolerant (ability to tolerate osmotic stress) nature. The objectives of this dissertation were to understand the factors that enhance the ability of Y. enterocolitica to survive and grow at low temperatures and at environments of high osmolarity. These objectives were accomplished by evaluating the ability of Y. enterocolitica to survive on pork at low temperatures; its ability to produce cold shock proteins; and its ability to accumulate osmolytes during osmotic stress. Results determined that chilling and freezing for extended periods of time did not reduce the population of Y. enterocolitica on pork. Also, Y. enterocolitica expressed the major cold shock proteins and genes in milk and pork when subjected to a temperature downshift from 30 to 4°C. Accumulation of osmolytes such as betaine is one of the major osmotolerance mechanisms of bacteria. Results of this study indicated that membrane transporters ProP and ProU may play an important role in betaine uptake by Y. enterocolitica when subjected to cold and osmotic stress.^