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Infection and Immunity, January 2001, p. 177-185, Vol. 69, No. 1
0019-9567/01/$04.00+0   DOI: 10.1128/IAI.69.1.177-185.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Legionella pneumophila Major Acid Phosphatase and Its Role in Intracellular Infection

Virginia Aragon, Sherry Kurtz, and Nicholas P. Cianciotto*

Department of Microbiology and Immunology, Northwestern University edical School, Chicago, Illinois 60611

Received 24 July 2000/Returned for modification 4 October 2000/Accepted 15 October 2000

Legionella pneumophila is an intracellular pathogen of protozoa and alveolar macrophages. This bacterium contains a gene (pilD) that is involved in both type IV pilus biogenesis and type II protein secretion. We previously demonstrated that the PilD prepilin peptidase is crucial for intracellular infection by L. pneumophila and that the secreted pilD-dependent proteins include a metalloprotease, an acid phosphatase, an esterase/lipase, a phospholipase A, and a p-nitrophenyl phosphorylcholine hydrolase. Since mutants lacking type IV pili, the protease, or the phosphorylcholine hydrolase are not defective for intracellular infection, we sought to determine the significance of the secreted acid phosphatase activity. Three mutants defective in acid phosphatase activity were isolated from a population of mini-Tn10-mutagenized L. pneumophila. Supernatants as well as cell lysates from these mutants contained minimal acid phosphatase activity while possessing normal levels of other pilD-dependent exoproteins. Genetic studies indicated that the gene affected by the transposon insertions encoded a novel bacterial histidine acid phosphatase, which we designated Map for major acid phosphatase. Subsequent inhibitor studies indicated that Map, like its eukaryotic homologs, is a tartrate-sensitive acid phosphatase. The map mutants grew within macrophage-like U937 cells and Hartmannella amoebae to the same degree as did wild-type legionellae, indicating that this acid phosphatase is not essential for L. pneumophila intracellular infection. However, in the course of characterizing our new mutants, we gained evidence for a second pilD-dependent acid phosphatase activity that, unlike Map, is tartrate resistant.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, Northwestern University Medical School, 320 East Superior Street, Chicago, IL 60611-3010. Phone: (312) 503-0385. Fax: (312) 503-1339. E-mail: n-cianciotto{at}northwestern.edu.

Infection and Immunity, January 2001, p. 177-185, Vol. 69, No. 1
0019-9567/01/$04.00+0   DOI: 10.1128/IAI.69.1.177-185.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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Copyright © 2001 by the American Society for Microbiology. All rights reserved.