Affiliation:
1. Department of Molecular Microbiology & Biotechnology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv, Tel-Aviv 69978, Israel
Abstract
ABSTRACT
Coxiella burnetii
, the etiological agent of Q fever, is an obligate intracellular pathogen, whereas
Legionella pneumophila
, the causative agent of Legionnaires' disease, is a facultative intracellular pathogen. During infection of humans both of these pathogens multiply in alveolar macrophages inside a closed phagosome.
L. pneumophila
intracellular multiplication was shown to be dependent on the
icm/dot
system, which probably encodes a type IV-related translocation apparatus. Recently, genes homologous to all of the
L. pneumophila icm
/
dot
genes (besides
icmR
) were found in
C. burnetii.
To explore the similarities and differences between the
icm/dot
pathogenesis systems of these two pathogens, interspecies complementation analysis was performed. Nine
C. burnetii icm
homologous genes (
icmT
,
icmS
,
icmQ
,
icmP
,
icmO
,
icmJ
,
icmB
,
icmW
, and
icmX
) were cloned under regulation of the corresponding
L. pneumophila icm
genes and examined for the ability to complement
L. pneumophila
mutants with mutations in these genes. The
C. burnetii icmS
and
icmW
homologous genes were found to complement the corresponding
L. pneumophila icm
mutants to wild-type levels of intracellular growth in both HL-60-derived human macrophages and
Acanthamoeba castellanii
. In addition, the
C. burnetii icmT
homologous gene was found to completely complement an
L. pneumophila
insertion mutant for intracellular growth in HL-60-derived human macrophages, but it only partially complemented the same mutant for intracellular growth in
A. castellanii
. Moreover, as previously shown for
L. pneumophila
, the proteins encoded by the
C. burnetii icmS
and
icmW
homologous genes were found to interact with one another, and interspecies protein interaction was observed as well. Our results strongly indicate that the Icm/Dot pathogenesis systems of
C. burnetii
and
L. pneumophila
have common features.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology