Identification of Mycobacterium avium pathogenicity island important for macrophage and amoeba infection

doi:10.1073/pnas.0610746104

Identification of Mycobacterium avium pathogenicity island important for macrophage and amoeba infection

Departments of *Biomedical Sciences, College of Veterinary Medicine, and
^¶Microbiology, College of Science, and
^§Environmental Health Sciences Center, Oregon State University, Corvallis, OR 97331; and
^‡Department of Veterinary and Biomedical Sciences, University of Nebraska, Lincoln, NE 68583-0905

Edited by E. Peter Greenberg, University of Washington School of Medicine, Seattle, WA, and approved May 17, 2007 (received for review December 4, 2006)

Abstract

The ability to infect macrophages is a common characteristic shared among many mycobacterial species. Mycobacterium avium, Mycobacterium tuberculosis, and Mycobacterium kansasii enter macrophages, using the complement receptors CR1, CR3, CR4, and the mannose receptor. To identify M. avium genes and host cell pathways involved in the bacterial uptake by macrophages, we screened a M. avium transposon mutant library for the inability to enter macrophages. Uptake-impaired clones were selected. Sequence of six M. avium clones identified one gene involved in glycopeptidolipid biosynthesis, one gene encoding the conserved membrane protein homologue to the M. avium subsp. paratuberculosis MAP2446c gene and four others belonging to the same region of the chromosome. Analysis of the chromosome region revealed a pathogenicity island inserted between two tRNA sequences with 58% of G+C content versus 69% in the M. avium genome. The region is unique for M. avium and is not present in M. tuberculosis or M. paratuberculosis. Although the mutants did not differ from the WT bacterium regarding the binding to macrophage cell membrane, analysis of macrophage proteins after 1 h infection revealed a deficiency in the mutant to phosphorylate certain proteins on uptake. To understand M. avium interaction with two evolutionarily distinct hosts, the mutants were evaluated for Acanthamoeba castellanii invasion. The defect in the ability of the mutants to invade both cells was highly similar, suggesting that M. avium might have evolved mechanisms that are used to enter amoebas and human macrophages.

uptake

Footnotes

^‖To whom correspondence should be addressed.
Department of Biomedical Sciences College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331-8797.
E-mail: luiz.bermudez{at}oregonstate.edu
Author contributions: L.D. and L.E.B. designed research; L.D., M.W., B.S., S.C., R.B., B.A., and L.E.B. performed research; M.H. contributed new reagents/analytic tools; L.D., M.W., B.S., M.H., J.C., and L.E.B. analyzed data; and L.D. and L.E.B. wrote the paper.
↵ ^†Present address: Department of Microbiology and Molecular Pathogenesis, Texas A & M University, College of Medicine, College Station, TX 77843–1114.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0610746104/DC1.
Abbreviation:

PI,

pathogenicity island.