Affiliation:
1. Department of Microbiology and Immunology, University of Kentucky Chandler Medical Center, Lexington, Kentucky 40536-0084
Abstract
ABSTRACT
We have recently described the expression of two pili of different lengths on the surface of
Legionella pneumophila
(B. J. Stone and Y. Abu Kwaik, Infect. Immun. 66:1768–1775, 1998). Production of long pili requires a functional
pilE
L
locus, encoding a type IV pilin protein. Since type IV pili in
Neisseria gonorrhoeae
are associated with competence for DNA transformation, we examined the competence of
L. pneumophila
for DNA transformation under conditions that allowed the expression of type IV pili. We show that
L. pneumophila
is naturally competent for DNA transformation by isogenic chromosomal DNA and by plasmid DNA containing
L. pneumophila
DNA. Many different
L. pneumophila
loci are able to transform
L. pneumophila
after addition of plasmid DNA, including
gspA
,
ppa
,
asd
, and
pilE
L
. The transformation frequency is reduced when competing DNA containing either
L. pneumophila
DNA or vector sequences is added to the bacteria, suggesting that uptake-specific sequences may not be involved in DNA uptake. Competence for DNA transformation correlates with expression of the type IV pili, and a
pilE
L
mutant defective in expression of type IV pili is not competent for DNA transformation. Complementation of the mutant for competence is restored by the reintroduction of a cosmid that restores production of type IV pili. Minimal competence is restored to the mutant by introduction of
pilE
L
alone. We conclude that competence for DNA transformation in
L. pneumophila
is associated with expression of the type IV pilus and results in recombination of
L. pneumophila
DNA into the chromosome. Since expression of type IV pili also facilitates attachment of
L. pneumophila
to mammalian cells and protozoa, we designated the type IV pili CAP (for competence- and adherence-associated pili).
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
170 articles.
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