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Journal of Bacteriology, February 2007, p. 1128-1137, Vol. 189, No. 3
0021-9193/07/$08.00+0     doi:10.1128/JB.01489-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

A Second Galacturonic Acid Transferase Is Required for Core Lipopolysaccharide Biosynthesis and Complete Capsule Association with the Cell Surface in Klebsiella pneumoniae{triangledown} ,{dagger}

Sandra Fresno,1 Natalia Jiménez,1 Rocío Canals,1 Susana Merino,1 Maria Michela Corsaro,3 Rosa Lanzetta,3 Michelangelo Parrilli,3 Giuseppina Pieretti,3 Miguel Regué,2 and Juan M. Tomás1*

Departamento de Microbiología, Facultad de Biología, Universidad de Barcelona, Diagonal 645, 08071 Barcelona, Spain,1 Departamento de Microbiología y Parasitología Sanitarias, Facultad de Farmacia, Universidad de Barcelona, Av. Joan XXIII s/n, Barcelona 08028, Spain,2 Dipartimento di Chimica Organica e Biochimica, Università Federico II di Napoli, Complesso Universitario Monte S. Angelo, Via Cintia 4, 80126 Napoli, Italy3

Received 21 September 2006/ Accepted 17 November 2006

The core lipopolysaccharide (LPS) of Klebsiella pneumoniae contains two galacturonic acid (GalA) residues, but only one GalA transferase (WabG) has been identified. Data from chemical and structural analysis of LPS isolated from a wabO mutant show the absence of the inner core ß-GalA residue linked to L-glycero-D-manno-heptose III (L,D-Hep III). An in vitro assay demonstrates that the purified WabO is able to catalyze the transfer of GalA from UDP-GalA to the acceptor LPS isolated from the wabO mutant, but not to LPS isolated from waaQ mutant (deficient in L,D-Hep III). The absence of this inner core ß-GalA residue results in a decrease in virulence in a capsule-dependent experimental mouse pneumonia model. In addition, this mutation leads to a strong reduction in cell-bound capsule. Interestingly, a K66 Klebsiella strain (natural isolate) without a functional wabO gene shows reduced levels of cell-bound capsule in comparison to those of other K66 strains. Thus, the WabO enzyme plays an important role in core LPS biosynthesis and determines the level of cell-bound capsule in Klebsiella pneumoniae.

* Corresponding author. Mailing address: Departamento de Microbiología, Facultad de Biologia, Universidad de Barcelona, Diagonal 645, 08071 Barcelona, Spain. Phone: (34) 934021486. Fax: (34) 934039047. E-mail: jtomas{at}ub.edu.

{triangledown} Published ahead of print on 1 December 2006.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, February 2007, p. 1128-1137, Vol. 189, No. 3
0021-9193/07/$08.00+0     doi:10.1128/JB.01489-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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