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Infection and Immunity, April 2001, p. 2502-2511, Vol. 69, No. 4
Departments of
Medicine1 and Microbiology and
Immunology,2 Emory University School of
Medicine, and Department of Veterans Affairs Medical
Center,3 Atlanta, Georgia
Received 18 October 2000/Returned for modification 2 January
2001/Accepted 12 January 2001
The clinically important serogroups B, C, Y, and W-135 of
Neisseria meningitidis produce sialic acid capsules that
are critical in pathogenesis. In each of these serogroups, the capsule
transport (ctrABCD) and capsule biosynthesis
(synABCD) operons are divergently transcribed from putative
promoters located in a 134-bp intergenic region (J. S. Swartley,
J. H. Ahn, L. J. Liu, C. M. Kahler, and D. S. Stephens, J. Bacteriol. 178:4052-4059, 1996). In this study we further
assessed the role of the intergenic sequence in the transcriptional
regulation of the sialic acid capsules of N. meningitidis. Insertional mutagenesis or deletions of the 134-bp sequence in the
serogroup B meningococcal strain NMB resulted in a marked reduction or
elimination of ctrABCD and synABCD
transcription, with a concomitant loss of encapsulation. Chromosomal
transcriptional lacZ-ermC reporter fusions of
syn and ctr promoters were constructed through
allelic exchange. Using these constructs, both operons were found to be
constitutively transcribed in meningococci, the biosynthesis operon
about fourfold higher than the transport operon. Both promoters showed
increased activity during stationary-phase growth. In addition to the
promoters, a 70-bp 5' untranslated region (UTR) upstream of
synA was found to have a direct repeat and an inverted
repeat that overlapped three putative integration host factor binding
sites. Mutation of this 70-bp UTR and of the direct repeat upregulated
both syn and ctr transcription. Regulation through the synA UTR was absent in a K1 Escherichia
coli strain that produces identical capsular polysaccharide,
implicating species-specific regulation. Meningococcal sialic acid
capsule expression is initiated by divergent promoters in a 134-bp
intergenic region, is repressed at the transcriptional level by the 5'
UTR of synA, is increased during stationary-phase growth,
and shows species-specific regulation. Transcriptional regulation is
another important control point for sialic capsule expression in
N. meningitidis.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.4.2502-2511.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Transcriptional Regulation of Divergent Capsule
Biosynthesis and Transport Operon Promoters in Serogroup B
Neisseria meningitidis

*
Corresponding author. Mailing address: Division of
Infectious Diseases, Emory University School of Medicine, 69 Butler
St., SE, Atlanta, GA 30303. Phone: (404) 728-7688. Fax: (404) 329-2210. E-mail: dstep01{at}emory.edu.
Present address: Office of Cooperative Research, Yale University,
New Haven, CT 06520.
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