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An integrated transcriptomic and proteomic analysis was undertaken to determine the physiological response of Escherichia coli O157:H7 Sakai to steady-state conditions relevant to low temperature and water activity conditions experienced during meat carcass chilling in cold air. The response of E. coli during exponential growth at 25 °C a_w 0.985, 14 °C a_w 0.985, 25 °C a_w 0.967, and 14 °C a_w 0.967 was compared with that of a reference culture (35 °C a_w 0.993). Gene and protein expression profiles of E. coli were more strongly affected by low water activity (a_w 0.967) than by low temperature (14 °C). Predefined group enrichment analysis revealed that a universal response of E. coli to all test conditions included activation of the master stress response regulator RpoS and the Rcs phosphorelay system involved in the biosynthesis of the exopolysaccharide colanic acid, as well as down-regulation of elements involved in chemotaxis and motility. However, colanic acid-deficient mutants were shown to achieve comparable growth rates to their wild-type parents under all conditions, indicating that colanic acid is not required for growth. In contrast to the transcriptomic data, the proteomic data revealed that several processes involved in protein synthesis were down-regulated in overall expression at 14 °C a_w 0.985, 25 °C a_w 0.967, and 14 °C a_w 0.967. This result suggests that during growth under these conditions, E. coli, although able to transcribe the required mRNA, may lack the cellular resources required for translation. Elucidating the global adaptive response of E. coli O157:H7 during exposure to chilling and water activity stress has provided a baseline of knowledge of the physiology of this pathogen.

Item Type:	Refereed Article
Keywords:	enterohemorrhagic Escherichia coli O157:H7 Sakai, public health, cold stress, water activity stress, osmotic stress
Research Division:	Biological Sciences
Research Group:	Biochemistry and cell biology
Research Field:	Cell metabolism
Objective Division:	Animal Production and Animal Primary Products
Objective Group:	Primary products from animals
Objective Field:	Primary products from animals not elsewhere classified
UTAS Author:	Kocharunchitt, C (Dr Chawalit Kocharunchitt)
UTAS Author:	Bowman, JP (Associate Professor John Bowman)
UTAS Author:	Ross, T (Professor Tom Ross)
ID Code:	68686
Year Published:	2012
Web of Science® Times Cited:	45
Deposited By:	Agricultural Science
Deposited On:	2011-03-17
Last Modified:	2015-02-02
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