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Infection and Immunity, March 2005, p. 1491-1505, Vol. 73, No. 3
0019-9567/05/$08.00+0     doi:10.1128/IAI.73.3.1491-1505.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Translocation and Surface Expression of Lipidated Serogroup B Capsular Polysaccharide in Neisseria meningitidis

Yih-Ling Tzeng,1,2 Anup K. Datta,3 Cristy A. Strole,4,{dagger} Michael A. Lobritz,1,{ddagger} Russell W. Carlson,3 and David S. Stephens1,2,4*

Division of Infectious Diseases, Department of Medicine,1 Department of Microbiology and Immunology, Emory University School of Medicine,4 Department of Veterans Affairs Medical Center, Atlanta,2 Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia3

Received 25 July 2004/ Returned for modification 7 October 2004/ Accepted 28 October 2004

The capsule of N. meningitidis serogroup B, ({alpha}2->8)-linked polysialic acid and the capsules of other meningococcal serogroups and of other gram-negative bacterial pathogens are anchored in the outer membrane through a 1,2-diacylglycerol moiety. Previous work on the meningococcal cps complex in Escherichia coli K-12 indicated that deletion of genes designated lipA and lipB caused intracellular accumulation of hyperelongated capsule polymers lacking the phospholipid substitution. To better understand the role of lip and lipB in capsule expression in a meningococcal background, the location, sequence, and relationship to related bacterial capsule genes were defined and specific mutations in lipA and lipB were generated in the serogroup B meningococcal strain NMB. The lipA and lipB genes are located on the 3' end of the ctr operon and are most likely transcribed independently. Inactivation of lipA, lipB, and both resulted in the same total levels of capsular polymer production as in the parental controls; however, these mutants were as sensitive as an unencapsulated mutant to killing by normal human serum. Immunogold electron microscopy and flow cytometric analyses revealed intracellular inclusions of capsular polymers in lipA, lipB, and lipA lipB mutants. Capsular polymers purified from lipA, lipB, and lipA lipB mutants were lipidated. The phospholipid anchor was shown by gas chromatography-mass spectroscopy analysis to be a phosphodiester-linked 1,2-dipalmitoyl (C16:0) glycerol moiety and was identical in structure to that found on the wild-type meningococcal capsule polymers. Thus, lipA and lipB do not encode proteins responsible for diacylglycerophosphatidic acid substitution of the meningococcal capsule polymer; rather, they are required for proper translocation and surface expression of the lipidated polymer.


* Corresponding author. Mailing address: Department of Veterans Affairs Medical Center, Research 151, Room 5A188, 1670 Clairmont Rd., Decatur, GA 30033. Phone: (404) 728-7688. Fax: (404) 329-2210. E-mail: dstep01{at}emory.edu.

Editor: J. N. Weiser

{dagger} Present address: GlaxoSmithKline, Department of Metabolic Diseases, Raleigh, N.C.

{ddagger} Present address: Case Western Reserve University, Cleveland, Ohio.


Infection and Immunity, March 2005, p. 1491-1505, Vol. 73, No. 3
0019-9567/05/$08.00+0     doi:10.1128/IAI.73.3.1491-1505.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.




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