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J. Bacteriol. doi:10.1128/JB.01270-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

CHARACTERIZATION OF HELICOBACTER PYLORI LYTIC TRANSGLYCOSYLASES Slt AND MltD

Unité de Pathogénie Bactérienne des Muqueuses, Institut Pasteur. Paris, France

^* To whom correspondence should be addressed. Email: bonecai{at}pasteur.fr.

	Abstract

Peptidoglycan (PG) is a cell wall heteropolymer essential for cell integrity. PG hydrolases participate in correct assembly of the PG layer and have been shown to be required for cell division, cell daughter separation and maintenance of bacterial morphology. In silico analysis of the Helicobacter pylori genomes identified three potential hydrolases, Slt, MltD and AmiA. This study was aimed at determining the roles of the putative lytic transglycosylases, Slt and MltD, in H. pylori morphology, growth, and PG metabolism. Single mutants were constructed in strain 26695 using a non-polar kanamycin cassette. The slt and mltD mutants formed normal bacillary and coccoid bacteria in exponential and stationary phase, respectively. The slt and mltD mutants had comparable growth rates to the parental strain. But, the mltD mutant displayed an enhance survival in stationary phase, compared to the wild type or the slt mutant. PG was purified from exponentially growing bacteria and from stationary phase, and its muropeptide composition was analyzed by high-pressure liquid chromatography. This analysis showed a modification of muropeptide composition indicating a lytic transglycosylase activity for MltD and Slt. Glycan strand analysis suggested that Slt and MltD have an exo- and endo-type of lytic transglycosylase activity, indicating that Slt is mainly involved in PG turnover and MltD in the rearrangement of the PG layer. In this study, we show the distinct roles of the lytic transglycosylases Slt and MltD in PG metabolism.

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