Temperature-dependent effect of sublethal levels of cinnamaldehyde on viability and morphology of Escherichia coli
Article first published online: 13 JUL 2012
© 2012 The Authors Journal of Applied Microbiology © 2012 The Society for Applied Microbiology
Journal of Applied Microbiology
Volume 113, Issue 3, pages 591–600, September 2012
How to Cite
Visvalingam, J. and Holley, R.A. (2012), Temperature-dependent effect of sublethal levels of cinnamaldehyde on viability and morphology of Escherichia coli . Journal of Applied Microbiology, 113: 591–600. doi: 10.1111/j.1365-2672.2012.05367.x
- Issue published online: 14 AUG 2012
- Article first published online: 13 JUL 2012
- Accepted manuscript online: 20 JUN 2012 09:19AM EST
- Manuscript Accepted: 18 JUN 2012
- Manuscript Revised: 7 JUN 2012
- Manuscript Received: 4 APR 2012
- Natural Sciences and Engineering Research Council of Canada
- cell elongation;
- cell injury;
- Escherichia coli ;
Effects of sublethal levels of cinnamaldehyde (CIN) on the viability and morphology of Escherichia coli O157:H7 and E. coli 8 WT were investigated at 6 and 37°C.
Methods and Results
The minimum inhibitory concentration of CIN against E. coli O157:H7 and E. coli 8WT was 400 mg l−1. At 37°C and ≤300 mg l−1, CIN delayed the multiplication of both strains, causing a ≤5 and ≤13 h lag, respectively. Delayed multiplication at ≤300 mg l−1 was partly due to cell elongation and injury as determined by LIVE/DEAD viability, CTC vitality and bis-(1,3-dibutylbarbituric acid) trimethine oxonol staining. The greatest extent of cell elongation (87%) and greatest mean length (6·4 μm) occurred with E. coli O157:H7 at 2-h exposure to 200 mg l−1 CIN. After initial delays in multiplication, both E. coli O157:H7 and E. coli 8WT returned to exponential growth and normal morphology before reaching the stationary phase. In contrast at 6°C, CIN at ≥100 mg l−1 prevented cell elongation which occurred in untreated control cells. Treatment with 200 or 300 mg l−1 CIN at 6°C was lethal to both E. coli strains. At 300 mg l−1, CIN caused a ≥5 log CFU ml−1 reduction at ≤3 days and completely inactivated both of these organisms, causing ≥7 log CFU ml−1 reduction at 7 days.
Sublethal levels of CIN at 37°C delayed the multiplication of E. coli cells by causing transient cell elongation, but at 6°C ≥200 mg l−1 CIN was lethal to E. coli.
Significance and Impact of the Study
Inhibition of cold-induced cell elongation and the enhanced lethal effect of CIN at 6°C against E. coli O157:H7 suggest that CIN may be useful for control of this pathogen at refrigeration temperatures.