Adherence of Aggregatibacter actinomycetemcomitans via serotype-specific polysaccharide antigens in lipopolysaccharides.
BACKGROUND
Gram-negative Aggregatibacter actinomycetemcomitans is recognized as an important periodontal pathogen. A striking property of this bacterium is its ability to form a tenacious biofilm adhering to abiotic surfaces. Both fimbrial and non-fimbrial adhesins are believed to be responsible for this ability. In our study, specific markerless mutants in the biosynthesis genes of cell surface polysaccharides were constructed with the Cre-loxP recombination system to identify non-fimbrial adhesin(s).


METHODS
Non-fimbriated A. actinomycetemcomitans strain ATCC29523 (serotype a) was used to construct a deletion mutant of serotype-a specific polysaccharide antigen (SPA-a) in lipopolysaccharide (LPS). The LPS was purified through a polymyxin B column following phenol extraction, and verified by silver staining following sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by immunoblot analysis using rabbit antisera raised against SPA-a. Strains were grown in broth for 2 days and examined for the adherence of bacterial cells on the glass surface.


RESULTS
Strain ATCC29523 formed a thin film of bacterial growth on the glass surface. The deletion of SPA-a affected its ability to form this thin film. When this mutant was rescued with the wild-type SPA-a gene cluster, its adherence-positive phenotype was restored.


CONCLUSIONS
SPA-a in the LPS molecule appears to promote the adherence of A. actinomycetemcomitans cells to abiotic surfaces.
Fujise
O
O
Kyushu University Faculty of Dental Science, Fukuoka, Japan. fujise@dent.kyushu-u.ac.jp
Wang
Y
Y
Chen
W
W
Chen
C
C
D018829:Adhesins, Bacterial / Q000235:genetics; D016976:Aggregatibacter actinomycetemcomitans / Q000145:classification / Q000235:genetics / Q000502:physiology*; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology*; D001422:Bacterial Adhesion / Q000235:genetics / Q000502:physiology*; D018441:Biofilms; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D017353:Gene Deletion; D005898:Glass; D006801:Humans; D019426:Integrases / Q000235:genetics; D008070:Lipopolysaccharides / Q000276:immunology*; D008970:Molecular Weight; D009154:Mutation / Q000235:genetics; D016366:Open Reading Frames / Q000235:genetics; D010957:Plasmids; D011135:Polysaccharides, Bacterial / Q000235:genetics / Q000276:immunology*; D012703:Serotyping
D018829:Adhesins, Bacterial; D000942:Antigens, Bacterial; D008070:Lipopolysaccharides; D011135:Polysaccharides, Bacterial; C045073:Cre recombinase; D019426:Integrases