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Infection and Immunity, May 2000, p. 2493-2502, Vol. 68, No. 5
Division of Infectious and Immunological
Diseases, Department of Pediatrics, and the Canadian Bacterial
Diseases Network,1 and Department of
Microbiology and Immunology,2 University of
British Columbia, Vancouver, British Columbia, Canada V5Z 4H4
Received 6 December 1999/Returned for modification 7 January
2000/Accepted 19 January 2000
Pseudomonas aeruginosa causes severe respiratory tract
infections in patients with cystic fibrosis (CF). We have been
examining nonopsonic phagocytosis of P. aeruginosa by
macrophages. To study the P. aeruginosa-macrophage
interaction at the molecular level, we have constructed a transposon
Tn5G bank in a clinical isolate of P. aeruginosa (strain 4020) and identified mutants resistant to
nonopsonic phagocytosis. Phagocytosis-resistant mutants were enriched
by passaging the transposon bank over 18 macrophage monolayers. Of 900 individual mutants isolated from this enriched pool in a nonopsonic
phagocytosis assay, we identified 85 putative mutants that were
resistant to phagocytosis. In this study, we have characterized one of
these transposon mutants, P. aeruginosa 4020 H27A, which was poorly ingested. H27A possessed a Tn5G insertion in a
gene encoding a protein with homology to the MotA proteins of several species of bacteria. We have called this gene rpmA for
required for phagocytosis by macrophages. RpmA is one of two MotA
paralogs in P. aeruginosa. This
rpmA::Tn5G mutant was motile both on
agar plates and in visual examination of wet mounts. The phagocytosis defect was partially complemented by providing the rpmA
gene in trans and fully complemented when both
rpmA and rpmB were provided. A rpmA
null mutant was ingested by macrophages similar to the H27A transposon
mutant. These data suggest that the rpmA and
rpmB gene products are required for the efficient ingestion
of P. aeruginosa by macrophages.
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
RpmA Is Required for Nonopsonic Phagocytosis of
Pseudomonas aeruginosa
*
Corresponding author. Mailing address: B.C. Research
Institute for Children's and Women's Health, 950 W 28th Ave., Rm.
381, Vancouver, BC, Canada V5Z 4H4. Phone: (604) 875-2469. Fax: (604) 875-2226. E-mail: dsimpson{at}cbdn.ca.
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