Genes Involved in the Synthesis and Degradation of Matrix Polysaccharide in <i>Actinobacillus actinomycetemcomitans</i> and <i>Actinobacillus pleuropneumoniae</i> Biofilms

<jats:title>ABSTRACT</jats:title> <jats:p> Biofilms are composed of bacterial cells embedded in an extracellular polysaccharide matrix. A major component of the <jats:italic>Escherichia coli</jats:italic> biofilm matrix is PGA, a linear polymer of <jats:italic>N</jats:italic> -acetyl- <jats:sc>d</jats:sc> -glucosamine residues in β(1,6) linkage. PGA mediates intercellular adhesion and attachment of cells to abiotic surfaces. In this report, we present genetic and biochemical evidence that PGA is also a major matrix component of biofilms produced by the human periodontopathogen <jats:italic>Actinobacillus actinomycetemcomitans</jats:italic> and the porcine respiratory pathogen <jats:italic>Actinobacillus pleuropneumoniae</jats:italic> . We also show that PGA is a substrate for dispersin B, a biofilm-releasing glycosyl hydrolase produced by <jats:italic>A. actinomycetemcomitans</jats:italic> , and that an orthologous dispersin B enzyme is produced by <jats:italic>A. pleuropneumoniae</jats:italic> . We further show that <jats:italic>A. actinomycetemcomitans</jats:italic> PGA cross-reacts with antiserum raised against polysaccharide intercellular adhesin, a staphylococcal biofilm matrix polysaccharide that is genetically and structurally related to PGA. Our findings confirm that PGA functions as a biofilm matrix polysaccharide in phylogenetically diverse bacterial species and suggest that PGA may play a role in intercellular adhesion and cellular detachment and dispersal in <jats:italic>A. actinomycetemcomitans</jats:italic> and <jats:italic>A. pleuropneumoniae</jats:italic> biofilms. </jats:p>