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Functional Analysis of D-Alanylation of Lipoteichoic Acid in the Probiotic Strain Lactobacillus rhamnosus GG

Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, 3001 Leuven, Belgium,¹ Department of Biochemical Pharmacology, University of Konstanz, D-78457 Konstanz, Germany,² Institute for Organic Chemistry, Philipps-Universität Marburg, D-35043 Marburg, Germany,³ Laboratory of Histology, BIOMED Research Institute, University Hasselt, Agoralaan Gebouw D, 3590 Diepenbeek, Belgium,⁴ Bactériologie des Écosystèmes, Institut Pasteur Lille, 59019 Lille Cedex, France⁵

Received 4 September 2006/ Accepted 24 March 2007

Lipoteichoic acid (LTA) is a macroamphiphile molecule which performs several functions in gram-positive bacteria, such as maintenance of cell wall homeostasis. D-Alanylation of LTA requires the proteins encoded by the dlt operon, and this process is directly related to the charge properties of this polymer strongly contributing to its function. The insertional inactivation of dltD of the probiotic strain Lactobacillus rhamnosus GG (ATCC 53103) resulted in the complete absence of D-alanyl esters in the LTA as confirmed by nuclear magnetic resonance analysis. This was reflected in modifications of the bacterial cell surface properties. The dltD strain showed 2.4-fold-increased cell length, a low survival capacity in response to gastric juice challenge, an increased sensitivity to human beta-defensin-2, an increased rate of autolysis, an increased capacity to initiate growth in the presence of an anionic detergent, and a decreased capacity to initiate growth in the presence of cationic peptides compared to wild-type results. However, in vitro experiments revealed no major differences for adhesion to human intestinal epithelial cells, biofilm formation, and immunomodulation. These properties are considered to be important for probiotics. The role of the dlt operon in lactobacilli is discussed in view of these results.

Published ahead of print on 13 April 2007.

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