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Applied and Environmental Microbiology, January 2003, p. 122-129, Vol. 69, No. 1
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.1.122-129.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

High pH during Trisodium Phosphate Treatment Causes Membrane Damage and Destruction of Salmonella enterica Serovar Enteritidis

Balamurugan Sampathkumar, George G. Khachatourians, and Darren R. Korber*

Department of Applied Microbiology and Food Science, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5A8, Canada

Received 29 May 2002/ Accepted 18 October 2002

Trisodium phosphate (TSP) is now widely used during the processing of poultry and red meats, but the mechanism whereby it inactivates gram-negative bacteria such Salmonella spp. remains unclear. Thus, Salmonella enterica serovar Enteritidis (ATCC 4931) cells were treated with different concentrations of TSP (1.5, 2.0, and 2.5% [wt/vol]) and compared with (i) cells treated with the same pH as the TSP treatments (pH 10.0, 10.5, and 11.0, respectively) and (ii) cells treated with different concentrations of TSP (1.5, 2.0, and 2.5% [wt/vol]) adjusted to a pH of 7.0 ± 0.2 (mean ± standard deviation). Cell viability, loss of membrane integrity, cellular leakage, release of lipopolysaccharides, and cell morphology were accordingly examined and quantified under the above treatment conditions. Exposure of serovar Enteritidis cells to TSP or equivalent alkaline pH resulted in the loss of cell viability and membrane integrity in a TSP concentration- or alkaline pH-dependent manner. In contrast, cells treated with different concentrations of TSP whose pH was adjusted to 7.0 did not show any loss of cell viability or membrane integrity. A 30-min pretreatment with 1.0 mM EDTA significantly enhanced the loss of membrane integrity only when followed by TSP or alkaline pH treatments. Measuring the absorbance at 260 nm, agarose gel electrophoresis, Bradford assay, and Tricine-sodium dodecyl sulfate gel electrophoresis of filtrates of treated cell suspensions revealed considerable release of DNA, proteins, and lipopolysaccharides compared to controls and pH 7.0 TSP treatments. Electron microscopic examination of TSP- or alkaline pH-treated cells showed disfigured cell surface topology and wrinkled appearance and showed evidence of a TSP concentration- and pH-dependent disruption of the cytoplasmic and outer membranes. These results demonstrate that TSP treatment permeabilizes and disrupts the cytoplasmic and outer membranes of serovar Enteritidis cells because of the alkaline pH, which in turn leads to release of intracellular contents and eventual cell death.

* Corresponding author. Mailing address: 51 Campus Dr., Department of Applied Microbiology and Food Science, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada. Phone: (306) 966-7786. Fax: (306) 966-8898. E-mail: korber{at}sask.usask.ca.

Applied and Environmental Microbiology, January 2003, p. 122-129, Vol. 69, No. 1
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.1.122-129.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Mangalappalli-Illathu, A. K., Vidovic, S., Korber, D. R. (2008). Differential Adaptive Response and Survival of Salmonella enterica Serovar Enteritidis Planktonic and Biofilm Cells Exposed to Benzalkonium Chloride. Antimicrob. Agents Chemother. 52: 3669-3680 [Abstract] [Full Text]  
  • Sampathkumar, B., Khachatourians, G. G., Korber, D. R. (2004). Treatment of Salmonella enterica Serovar Enteritidis with a Sublethal Concentration of Trisodium Phosphate or Alkaline pH Induces Thermotolerance. Appl. Environ. Microbiol. 70: 4613-4620 [Abstract] [Full Text]  


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