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Journal of Bacteriology, February 2004, p. 730-739, Vol. 186, No. 3
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.3.730-739.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

A Mutant Form of the Neisseria gonorrhoeae Pilus Secretin Protein PilQ Allows Increased Entry of Heme and Antimicrobial Compounds{dagger}

Ching-ju Chen,1* Deborah M. Tobiason,2 Christopher E. Thomas,1 William M. Shafer,3,4 H. Steven Seifert,2 and P. Frederick Sparling1,5

Department of Medicine,1 Department of Microbiology and Immunology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7031,5 Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611,2 Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia 30322,3 Laboratory of Bacterial Pathogenesis, Veterans Affairs Medical Center, Decatur, Georgia 300334

Received 18 August 2003/ Accepted 30 October 2003

A spontaneous point mutation in pilQ (pilQ1) resulted in phenotypic suppression of a hemoglobin (Hb) receptor mutant (hpuAB mutant), allowing gonococci to grow on Hb as the sole source of iron. PilQ, formerly designated OMP-MC, is a member of the secretin family of proteins located in the outer membrane and is required for pilus biogenesis. The pilQ1 mutant also showed decreased piliation and transformation efficiency. Insertional inactivation of pilQ1 resulted in the loss of the Hb utilization phenotype and decreased entry of free heme. Despite the ability of the pilQ1 mutant to use Hb for iron acquisition and porphyrin, there was no demonstrable binding of Hb to the cell surface. The pilQ1 mutant was more sensitive to the toxic effect of free heme in growth medium and hypersensitive to the detergent Triton X-100 and multiple antibiotics. Double mutation in pilQ1 and tonB had no effect on these phenotypes, but a double pilQ1 pilT mutant showed a reduction in Hb-dependent growth and decreased sensitivity to heme and various antimicrobial agents. Insertional inactivation of wild-type pilQ also resulted in reduced entry of heme, Triton X-100, and some antibiotics. These results show that PilQ forms a channel that allows entry of heme and certain antimicrobial compounds and that a gain-of function point mutation in pilQ results in TonB-independent, PilT-dependent increase of entry.

* Corresponding author. Mailing address: 8341 Medical Biomolecular Research Bldg., 103 Mason Farm Rd., University of North Carolina, Department of Medicine/ID-Research, CB#7031, Chapel Hill, NC 27599-7031. Phone: (919) 966-3661. Fax: (919) 843-1015. E-mail: chencj{at}med.unc.edu.

{dagger} This paper is dedicated to the memory of the late Igor Stojiljkovic.

Journal of Bacteriology, February 2004, p. 730-739, Vol. 186, No. 3
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.3.730-739.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



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