title: Examination of the genome-wide transcriptional response of Escherichia coli O157:H7 to cinnamaldehyde exposure.
abstract: Cinnamaldehyde is a natural antimicrobial that has been found to be effective against many food-borne pathogens, including Escherichia coli O157:H7. Although its antimicrobial effects have been well investigated, limited information is available on its effects at the molecular level. Sublethal treatment at 200 mg/liter cinnamaldehyde inhibited growth of E. coli O157:H7 at 37°C and for ≤2 h caused cell elongation, but from 2 to 4 h growth resumed and cells reverted to normal length. To understand this transient behavior, genome-wide transcriptional analysis of E. coli O157:H7 was performed at 2 and 4 h of exposure to cinnamaldehyde in conjunction with reverse-phase high-performance liquid chromatography (RP-HPLC) analysis for cinnamaldehyde and other cinnamic compounds. Drastically different gene expression profiles were obtained at 2 and 4 h. RP-HPLC analysis showed that cinnamaldehyde was structurally stable for at least 2 h. At 2 h of exposure, cinnamaldehyde induced expression of many oxidative stress-related genes and repressed expression of DNA, protein, O-antigen, and fimbrial synthetic genes. At 4 h, many cinnamaldehyde-induced repressive effects on E. coli O157:H7 gene expression were reversed, and cells became more motile and grew at a slightly higher rate. Data indicated that by 4 h, E. coli O157:H7 was able to convert cinnamaldehyde into the less toxic cinnamic alcohol using dehydrogenase/reductase enzymes (YqhD and DkgA). This is the first study to characterize the ability of E. coli O157:H7 to convert cinnamaldehyde into cinnamic alcohol which, in turn, showed that the antimicrobial activity of cinnamaldehyde is mainly attributable to its carbonyl aldehyde group.
authors.affiliation: Department of Food Science, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Jeyachchandran
authors.initials: J
authors.lastname: Visvalingam
authors.forename: Juan David
authors.initials: JD
authors.lastname: Hernandez-Doria
authors.forename: Richard A
authors.initials: RA
authors.lastname: Holley
mesh_terms: D000171:Acrolein / Q000031:analogs & derivatives* / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D019453:Escherichia coli O157 / Q000737:chemistry / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development; D020869:Gene Expression Profiling; D018384:Oxidative Stress; D013312:Stress, Physiological; D013696:Temperature; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D000171:Acrolein; C012843:cinnamaldehyde