Integrated Transcriptomic and Proteomic Analysis of the Physiological Response of Escherichia coli O157:H7 Sakai to Steady-state Conditions of Cold and Water Activity Stress

Abstract

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.

Global Genome Response of Escherichia coli O157∶H7 Sakai during Dynamic Changes in Growth Kinetics Induced by an Abrupt Temperature Downshift

“…This is consistent with low temperature induction of RpoS under steady state conditions previously reported [11], [84]. Nineteen genes exhibited greater than a 1-log 2 fold increase in expression from 90 min onwards and included genes involved in the osmotic stress response ( osmY ), acid response ( gadX ), biofilm formation ( bolA ), cell wall biogenesis ( erfK ), encoding an inner membrane protein ( yqjE ), predicted outer membrane protein ( ybaY ), hypothetical proteins ( yahO , yaiA , yccJ , ydiZ , yodC , yqjCD , yhhA , ytfK , ygaM ) and putative and predicted transcriptional regulators ( yiaG , yjbJ , nsrR ).…”

“…The cluster analysis (Figure 3) did not reveal a close similarity between the expression response profiles elicited by E. coli during exponential phase growth (160 and 330 min) and the expression response observed in our previous study monitoring the growth of E. coli during exponential growth at the same temperature (14°C a w 0.985) [11]. This may be accounted for, in part, by the difference in water activity in the current study (a w 0.993) and the previous study (a w 0.985) [11].…”

Omics approaches in food safety: fulfilling the promise?

“…Modulation of gene and protein expression in response to stress indicates activation or repression of a specific physiological response, and can be used to determine the physiological state of the pathogen under different conditions. A number of studies over the past 10 years have assessed transcriptomes and/or proteomes of bacteria under conditions simulating those a pathogen may experience on a food, such as the low water activity and low temperature that E. coli O157:H7 could encounter during beef carcass chilling [48]. Other recent studies have evaluated changes in gene expression of pathogens inoculated onto actual food products, such as Salmonella on cilantro and lettuce [49], E. coli O157:H7 on lettuce [50], and L. monocytogenes in milk [51].…”

Global Regulator of Virulence A (GrvA) Coordinates Expression of Discrete Pathogenic Mechanisms in Enterohemorrhagic Escherichia coli through Interactions with GadW-GadE

“…In strains of E. coli O157:H7 harboring a 49-bp deletion in rcsB, trans-complementation with wild-type rcsB decreased grvA expression (64). This was observed, however, only during culture at 28°C and correlates with reduced grvA expression during growth at 14°C and 25°C (65). Together, this suggests that regulation of grvA by RcsB is temperature sensitive.…”