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Infection and Immunity, December 2000, p. 6685-6690, Vol. 68, No. 12
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Multiple Mechanisms of Phase Variation of PorA in Neisseria meningitidis

Arie van der Ende,* Carla T. P. Hopman, and Jacob Dankert

Department of Medical Microbiology, Academic Medical Center, University of Amsterdam, and Reference Laboratory for Bacterial Meningitis, University of Amsterdam/RIVM, 1100 DE Amsterdam, The Netherlands

Received 6 July 2000/Returned for modification 14 August 2000/Accepted 25 September 2000

Previously, we reported that PorA expression in Neisseria meningitidis is modulated by variation in the length of the homopolymeric tract of guanidine residues between the -35 and -10 regions of the promoter or by deletion of porA. To reveal additional mechanisms of variation in PorA expression, the meningococcal isolates from 41 patients and 19 carriers were studied. In addition, at least 3 meningococcal isolates from different body parts of each of 11 patients were analyzed. Sequence analysis of the porA promoter showed that the spacer between the -35 and -10 regions varies in length between 14 and 24 bp. PorA expression was observed in strains with a porA promoter spacer of 16 to 24 bp. All but one strain with a porA promoter spacer of 16 to 20 bp and undetectable PorA expression have a homopolymeric tract of 8 or 6 instead of 7 adenine residues in the porA coding region. The other PorA-negative strain had a single-base-pair deletion in the coding region. The highest level of PorA expression was observed in strains with a promoter spacer of 17 or 18 bp. PorA expression was reduced twofold in strains with a porA promoter spacer of 16 or 19 bp. Strains with a 16-bp promoter spacer with substitutions in the polyguanidine tract displayed increased levels of PorA expression compared to strains with a homopolymeric tract of guanidine residues in the porA promoter. In conclusion, meningococci display multiple mechanisms for varying PorA expression.

* Corresponding author. Mailing address: Department of Medical Microbiology, Academic Medical Center, University of Amsterdam, P.O. Box 22700, 1100 DE Amsterdam, The Netherlands. Phone: (31-20) 5664862. Fax: (31-20) 6979271. E-mail: a.vanderende{at}amc.uva.nl.

Infection and Immunity, December 2000, p. 6685-6690, Vol. 68, No. 12
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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