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Front Microbiol. 2019 Apr 5;10:604. doi: 10.3389/fmicb.2019.00604. eCollection 2019.

Polymorphisms of a Collagen-Like Adhesin Contributes to Legionella pneumophila Adhesion, Biofilm Formation Capacity and Clinical Prevalence.

Abdel-Nour M1,2,3, Su H4, Duncan C1, Li S4, Raju D5,6, Shamoun F5,6, Valton M1,2,7, Ginevra C8,9,10,11, Jarraud S8,9,10,11, Guyard C1,2,3,12, Kerman K4, Terebiznik MR5,6.

Author information

1
Ontario Agency for Health Protection and Promotion, Toronto, ON, Canada.
2
Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.
3
The Mount Sinai Hospital, Toronto, ON, Canada.
4
Department of Physical & Environmental Sciences, University of Toronto Scarborough, Toronto, ON, Canada.
5
Department of Biological Sciences, University of Toronto at Scarborough, Toronto, ON, Canada.
6
Department of Cell and Systems Biology, University of Toronto at Scarborough, Toronto, ON, Canada.
7
Polytech Clermont-Ferrand, Aubière, France.
8
CIRI-International Center for Infectiology Research, Legionella Pathogenesis Team, Université de Lyon, Lyon, France.
9
INSERM U1111, Lyon, France.
10
Centre International de Recherche en Infectiologie, Claude Bernard University Lyon 1, Lyon, France.
11
National Center for Legionella, Hospices Civils de Lyon, Lyon, France.
12
BIOASTER Microbiology Technology Institute, Lyon, France.

Abstract

Legionellosis is a severe respiratory illness caused by the inhalation of aerosolized water droplets contaminated with the opportunistic pathogen Legionella pneumophila. The ability of L. pneumophila to produce biofilms has been associated with its capacity to colonize and persist in human-made water reservoirs and distribution systems, which are the source of legionellosis outbreaks. Nevertheless, the factors that mediate L. pneumophila biofilm formation are largely unknown. In previous studies we reported that the adhesin Legionella collagen-like protein (Lcl), is required for auto-aggregation, attachment to multiple surfaces and the formation of biofilms. Lcl structure contains three distinguishable regions: An N-terminal region with a predicted signal sequence, a central region containing tandem collagen-like repeats (R-domain) and a C-terminal region (C-domain) with no significant homology to other known proteins. Lcl R-domain encodes tandem repeats of the collagenous tripeptide Gly-Xaa-Yaa (GXY), a motif that is key for the molecular organization of mammalian collagen and mediates the binding of collagenous proteins to different cellular and environmental ligands. Interestingly, Lcl is polymorphic in the number of GXY tandem repeats. In this study, we combined diverse biochemical, genetic, and cellular approaches to determine the role of Lcl domains and GXY repeats polymorphisms on the structural and functional properties of Lcl, as well as on bacterial attachment, aggregation and biofilm formation. Our results indicate that the R-domain is key for assembling Lcl collagenous triple-helices and has a more preponderate role over the C-domain in Lcl adhesin binding properties. We show that Lcl molecules oligomerize to form large supramolecular complexes to which both, R and C-domains are required. Furthermore, we found that the number of GXY tandem repeats encoded in Lcl R-domain correlates positively with the binding capabilities of Lcl and with the attachment and biofilm production capacity of L. pneumophila strains. Accordingly, the number of GXY tandem repeats in Lcl influences the clinical prevalence of L. pneumophila strains. Therefore, the number of Lcl tandem repeats could be considered as a potential predictor for virulence in L. pneumophila isolates.

KEYWORDS:

Legionella pneumophila; adhesion; biofilm; cell–cell adhesion; clinical prevalence; collagen-like adhesion

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