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Infection and Immunity, April 2009, p. 1389-1396, Vol. 77, No. 4
0019-9567/09/$08.00+0     doi:10.1128/IAI.01215-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Identification of a Pneumococcal Glycosidase That Modifies O-Linked Glycans{triangledown}

Carolyn Marion,1,2 Dominique H. Limoli,1 Gregory S. Bobulsky,1,2 Jessica L. Abraham,1,2 Amanda M. Burnaugh,1 and Samantha J. King1,2*

Center for Microbial Pathogenesis, The Research Institute at Nationwide Children's Hospital,1 Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio2

Received 2 October 2008/ Returned for modification 15 November 2008/ Accepted 5 January 2009

Colonization of the airway by Streptococcus pneumoniae is typically asymptomatic; however, progression of bacteria beyond the oronasopharynx can cause diseases including otitis media and pneumonia. The mechanisms by which S. pneumoniae establishes and maintains colonization remain poorly understood. Both N-linked and O-linked glycans are abundant in the airway. Our previous research demonstrated that S. pneumoniae can sequentially deglycosylate N-linked glycans and suggested that this modification of sugar structures may aid in colonization. There is published evidence that S. pneumoniae expresses a secreted O-glycosidase that cleaves galactose β1-3 N-acetylgalactosamine (Galβ1-3GalNAc) from core-1 O-linked glycans; however, the biological function of this enzyme has not previously been determined. We established that the activity is not secreted but is instead surface associated in a sortase-dependent manner. Genome analysis revealed an open reading frame predicted to encode a sortase-dependent surface protein with sequence similarity to the O-glycosidase of Bifidobacterium longum. Deletion of this pneumococcal open reading frame confirmed that this gene encodes an O-glycosidase. Experiments using a model glycoconjugate demonstrated that this O-glycosidase, together with the neuraminidase NanA, is required for S. pneumoniae to cleave sialylated core-1 O-linked glycans. The ability of the O-glycosidase mutant to cleave this glycan structure was restored by both genetic complementation and the addition of O-glycosidase. The mutant showed a reduction in adherence to human airway epithelial cells and a significantly decreased ability to colonize the upper respiratory tract, suggesting that cleavage of core-1 O-linked glycans enhances the ability of S. pneumoniae to colonize the human airway.

* Corresponding author. Mailing address: The Research Institute at Nationwide Children's Hospital, Center for Microbial Pathogenesis, Room W511, 700 Children's Drive, Columbus, OH 43205-2696. Phone: (614) 722-2912. Fax: (614) 722-2818. E-mail: KingS{at}pediatrics.ohio-state.edu

{triangledown} Published ahead of print on 12 January 2009.

Editor: A. Camilli

Infection and Immunity, April 2009, p. 1389-1396, Vol. 77, No. 4
0019-9567/09/$08.00+0     doi:10.1128/IAI.01215-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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