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Applied and Environmental Microbiology, July 2008, p. 4434-4439, Vol. 74, No. 14
0099-2240/08/$08.00+0     doi:10.1128/AEM.00589-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Role of the Lysozyme Inhibitor Ivy in Growth or Survival of Escherichia coli and Pseudomonas aeruginosa Bacteria in Hen Egg White and in Human Saliva and Breast Milk{triangledown}

Daphne Deckers, Dietrich Vanlint, Lien Callewaert, Abram Aertsen, and Chris W. Michiels*

Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Center (LFoRCe), Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium

Received 12 March 2008/ Accepted 20 May 2008

Ivy is a lysozyme inhibitor that protects Escherichia coli against lysozyme-mediated cell wall hydrolysis when the outer membrane is permeabilized by mutation or by chemical or physical stress. In the current work, we have investigated whether Ivy is necessary for the survival or growth of E. coli MG1655 and Pseudomonas aeruginosa PAO1 in hen egg white and in human saliva and breast milk, which are naturally rich in lysozyme and in membrane-permeabilizing components. Wild-type E. coli was able to grow in saliva and breast milk but showed partial inactivation in egg white. The knockout of Ivy did not affect growth in breast milk but slightly increased sensitivity to egg white and caused hypersensitivity to saliva, resulting in the complete inactivation of 104 CFU ml–1 of bacteria within less than 5 hours. The depletion of lysozyme from saliva completely restored the ability of the ivy mutant to grow like the parental strain. P. aeruginosa, in contrast, showed growth in all three substrates, which was not affected by the knockout of Ivy production. These results indicate that lysozyme inhibitors like Ivy promote bacterial survival or growth in particular lysozyme-rich secretions and suggest that they may promote the bacterial colonization of specific niches in the animal host.

* Corresponding author. Mailing address: Laboratory of Food Microbiology, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium. Phone: 32-16-321578. Fax: 32-16-321960. E-mail: Chris.Michiels{at}biw.kuleuven.be

{triangledown} Published ahead of print on 30 May 2008.

Applied and Environmental Microbiology, July 2008, p. 4434-4439, Vol. 74, No. 14
0099-2240/08/$08.00+0     doi:10.1128/AEM.00589-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Callewaert, L., Vanderkelen, L., Deckers, D., Aertsen, A., Robben, J., Michiels, C. W. (2008). Detection of a Lysozyme Inhibitor in Proteus mirabilis by a New Reverse Zymogram Method. Appl. Environ. Microbiol. 74: 4978-4981 [Abstract] [Full Text]  


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