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Global genome response of Escherichia coli O157?H7 Sakai during dynamic changes in growth kinetics induced by an abrupt downshift in water activity.

ABSTRACT: The present study was undertaken to investigate growth kinetics and time-dependent change in global expression of Escherichia coli O157?H7 Sakai upon an abrupt downshift in water activity (aw). Based on viable count data, shifting E. coli from aw 0.993 to aw 0.985 or less caused an apparent loss, then recovery, of culturability. Exponential growth then resumed at a rate characteristic for the aw imposed. To understand the responses of this pathogen to abrupt osmotic stress, we employed an integrated genomic and proteomic approach to characterize its cellular response during exposure to a rapid downshift but still within the growth range from aw 0.993 to aw 0.967. Of particular interest, genes and proteins with cell envelope-related functions were induced during the initial loss and subsequent recovery of culturability. This implies that cells undergo remodeling of their envelope composition, enabling them to adapt to osmotic stress. Growth at low aw, however, involved up-regulating additional genes and proteins, which are involved in the biosynthesis of specific amino acids, and carbohydrate catabolism and energy generation. This suggests their important role in facilitating growth under such stress. Finally, we highlighted the ability of E. coli to activate multiple stress responses by transiently inducing the RpoE and RpoH regulons to control protein misfolding, while simultaneously activating the master stress regulator RpoS to mediate long-term adaptation to hyperosmolality. This investigation extends our understanding of the potential mechanisms used by pathogenic E. coli to adapt, survive and grow under osmotic stress, which could potentially be exploited to aid the selection and/or development of novel strategies to inactivate this pathogen.

SUBMITTER: Kocharunchitt C

PROVIDER: S-EPMC3940904 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Global genome response of Escherichia coli O157∶H7 Sakai during dynamic changes in growth kinetics induced by an abrupt downshift in water activity.

Kocharunchitt Chawalit C King Thea T Gobius Kari K Bowman John P JP Ross Tom T

PloS one 20140303 3

The present study was undertaken to investigate growth kinetics and time-dependent change in global expression of Escherichia coli O157∶H7 Sakai upon an abrupt downshift in water activity (aw). Based on viable count data, shifting E. coli from aw 0.993 to aw 0.985 or less caused an apparent loss, then recovery, of culturability. Exponential growth then resumed at a rate characteristic for the aw imposed. To understand the responses of this pathogen to abrupt osmotic stress, we employed an integr ...[more]

PMID: 24594867

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Project description:Enterohemeorrhagic Escherichia coli is a leading cause of foodborne illness, with the majority of cases linked to foods of bovine origin. Currently, no completely effective method for controlling this pathogen during carcass processing exists. Understanding how this pathogen behaves under those stress conditions experienced on the carcass during chilling in cold air could offer opportunities for development or improvement of effective decontamination processes. Therefore, we studied the growth kinetics and physiological response of exponential phase E. coli O157:H7 Sakai cultures upon an abrupt downshift in temperature and water activity (from 35 °C aw 0.993 to 14 °C aw 0.967). A parallel Biolog study was conducted to follow the phenotypic responses to 190 carbon sources. Exposure of E. coli to combined cold and water activity stresses resulted in a complex pattern of population changes. This pattern could be divided into two main phases, including adaptation and regrowth phases, based on growth kinetics and clustering analyses. The transcriptomic and proteomic studies revealed that E. coli exhibited a "window" of cell susceptibility (i.e. weaknesses) during adaptation phase. This included apparent DNA damage, the downregulation of molecular chaperones and proteins associated with responses to oxidative damage. However, E. coli also displayed a transient induction in the RpoE-controlled envelope stress response and activation of the master stress regulator RpoS and the Rcs phosphorelay system involved in colanic acid biosynthesis. Increased expression was observed for several genes and/or proteins involved in DNA repair, protein and peptide degradation, amino acid biosynthesis, and carbohydrate catabolism and energy generation. Furthermore, the Biolog study revealed reduced carbon source utilization during adaptation phase, indicating the disruption of energy-generating processes. This study provides insight into the physiological response of E. coli during exposure to combined cold and water activity stress, which could be exploited to enhance the microbiological safety of carcasses and related foods.

Dataset Information

Global genome response of Escherichia coli O157?H7 Sakai during dynamic changes in growth kinetics induced by an abrupt downshift in water activity.

Publications

Global genome response of Escherichia coli O157∶H7 Sakai during dynamic changes in growth kinetics induced by an abrupt downshift in water activity.

Similar Datasets

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