Surface Polysaccharide Mutants Reveal that Absence of O Antigen Reduces Biofilm Formation of Actinobacillus pleuropneumoniae.
Actinobacillus pleuropneumoniae is a Gram-negative bacterium belonging to the Pasteurellaceae family and the causative agent of porcine pleuropneumonia, a highly contagious lung disease causing important economic losses. Surface polysaccharides, including lipopolysaccharides (LPS) and capsular polysaccharides (CPS), are implicated in the adhesion and virulence of A. pleuropneumoniae, but their role in biofilm formation is still unclear. In this study, we investigated the requirement for these surface polysaccharides in biofilm formation by A. pleuropneumoniae serotype 1. Well-characterized mutants were used: an O-antigen LPS mutant, a truncated core LPS mutant with an intact O antigen, a capsule mutant, and a poly-N-acetylglucosamine (PGA) mutant. We compared the amount of biofilm produced by the parental strain and the isogenic mutants using static and dynamic systems. Compared to the findings for the biofilm of the parental or other strains, the biofilm of the O antigen and the PGA mutants was dramatically reduced, and it had less cell-associated PGA. Real-time PCR analyses revealed a significant reduction in the level of pgaA, cpxR, and cpxA mRNA in the biofilm cells of the O-antigen mutant compared to that in the biofilm cells of the parental strain. Specific binding between PGA and LPS was consistently detected by surface plasmon resonance, but the lack of O antigen did not abolish these interactions. In conclusion, the absence of the O antigen reduces the ability of A. pleuropneumoniae to form a biofilm, and this is associated with the reduced expression and production of PGA.
Groupe de Recherche sur les Maladies Infectieuses du Porc, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Québec, Canada.
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S
Hathroubi
McGill Surface Plasmon Resonance-Mass Spectrometry Facility, McGill University, Montréal, Québec, Canada.
M A
MA
Hancock
Section of Paediatrics, Imperial College London, London, United Kingdom.
J T
http://orcid.org/0000-0002-8491-4779
JT
Bossé
Section of Paediatrics, Imperial College London, London, United Kingdom.
P R
PR
Langford
Groupe de Recherche sur les Maladies Infectieuses du Porc, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Québec, Canada.
Y D N
YD
Tremblay
Groupe de Recherche sur les Maladies Infectieuses du Porc, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Québec, Canada.
J
J
Labrie
Groupe de Recherche sur les Maladies Infectieuses du Porc, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Québec, Canada mario.jacques@umontreal.ca.
M
M
Jacques
D000189:Actinobacillus Infections / Q000382:microbiology; D016977:Actinobacillus pleuropneumoniae / Q000235:genetics / Q000472:pathogenicity*; D000818:Animals; D001422:Bacterial Adhesion / Q000235:genetics*; D016667:Bacterial Capsules / Q000235:genetics / Q000276:immunology; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics; D018441:Biofilms / Q000254:growth & development*; D008070:Lipopolysaccharides / Q000235:genetics* / Q000378:metabolism; D019081:O Antigens / Q000235:genetics* / Q000276:immunology; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D008070:Lipopolysaccharides; D019081:O Antigens; C085504:CpxR protein, Bacteria; D011494:Protein Kinases; C092472:CpxA protein, bacteria