The outer membrane autotransporters Fap2 and CmpA facilitate specific coaggregation between <i>Fusobacterium nucleatum</i> and <i>Aggregatibacter actinomycetemcomitans</i> serotypes b and d

<i>Fusobacterium nucleatum</i> is a periodontal pathogen that acts as a bridging organism by coaggregating with various oral microbes, including other periodontal pathogens. Recently, this bacterium has been reported to be associated with systemic diseases, including cardiovascular diseases, adverse pregnancy outcomes, and cancer. <i>F. nucleatum</i> possesses numerous adhesins, including autotransporter proteins that are considered to mediate colonization in human tissues. Our study demonstrated that <i>F. nucleatum</i> utilizes two autotransporter proteins (Fap2 and CmpA) to coaggregate with another periodontal pathogen, <i>Aggregatibacter actinomycetemcomitans</i>, through specific interactions with bacterial surface polysaccharides. In addition to the roles of these autotransporters in periodontitis through bacterial coaggregation with other oral bacterial species, our findings potentially provide new insights into the mechanism underlying systemic diseases caused by <i>F. nucleatum</i> binding to host cell carbohydrates and glycoproteins.