Examination of stress and virulence gene expression in Escherichia coli O157:H7 using targeted microarray analysis.
Escherichia coli O157:H7 poses a threat to humans through food- and water-borne transmission. To investigate how environmental stresses affect the Escherichia coli O157:H7 transcriptome, we designed a targeted microarray consisting of stress response and virulence genes (n = 125) to analyze the impact of acidified (pH 3.5), cold (7.5 degrees C), and fresh tryptic soy broth (TSB) (37 degrees C) on E. coli O157:H7 stress response and virulence gene expression. Nutrient replenishment with fresh TSB resulted in 72 differentially expressed genes (> or = 1.5-fold change; p < 0.05), with 65 induced. All queried global and specific stress regulators were affected, as were 12 virulence genes. Cold-shocked cells displayed 17 differentially expressed genes, with 10 being induced. Induction of rpoS, members of the sigma(H) regulon (clpB, dnaK, ftsH), and acid resistance (AR) genes (gadA, gadX) was observed. Porin transcript (ompC, ompF) and gapA and tufA ancillary genes were repressed. Acid shock resulted in 24 differentially expressed genes, with 21 induced. No induction of any stationary phase AR system was observed, though acid-coping mechanisms were recruited, including mar and phoB induction, and repression of ompC and ompF. Stress regulators were induced, including relA, soxS, rpoE, and rpoH. The microarray data were validated by quantitative real-time polymerase chain reaction. Exposure to sublethal stress events led to the induction of diverse stress response networks. In the food chain, sublethal events may render cells increasingly resistant to future stresses, potentially leading to increased survival.
Allen
Kevin J
KJ
Department of Food Science and Canadian Research Institute for Food Safety, University of Guelph, Guelph, Ontario, Canada.
Lepp
Dion
D
McKellar
Robin C
RC
Griffiths
Mansel W
MW
D001426:Bacterial Proteins / Q000235:genetics; D003080:Cold Temperature; D019453:Escherichia coli O157 / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics; D005516:Food Microbiology; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006863:Hydrogen-Ion Concentration; D053858:Metabolic Networks and Pathways / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D012329:RNA, Bacterial / Q000235:genetics; D018085:Regulon; D012808:Sigma Factor / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics*
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012808:Sigma Factor; D037521:Virulence Factors; C069567:sigma factor KatF protein, Bacteria