Interactions between different bacteria play an important role in biofilm development during primary colonization of the human tooth surface. Well studied examples of such interactions include the receptor polysaccharide (RPS)-mediated interactions between viridans group streptococci and other oral bacteria including type 2 fimbriated Actinomyces naeslundii. Previous studies have resulted in the identification of different structural, antigenic and molecular types of RPS on the streptococci that initiate colonization of the tooth surface. This information provides the basis for the current protocol, which addresses a number of important questions involving the nature of the commensal relationship that exists between biofilm-forming bacteria and the host. For example: (1) How many types of RPS are produced by the resident flora of an individual at any one time? (2) Does the resident population of RPS-producing clones change over the lifetime of the host? (3) Do individuals produce secretory antibodies against bacterial RPS, and if so, does this drive a change in the antigenic type of RPS produced? (3) When and how do infants acquire RPS-producing bacteria, before or after tooth eruption? To address these questions, we wish to collect and analyze samples of early dental plaque from the members of individual families. The collection of such samples will be accomplished by gently rubbing exposed tooth surfaces with a sterile cotton swab. Adult volunteers will also be asked to provide small samples of saliva, which will be assayed for the presence of specific anti-RPS antibodies. The sampling procedures proposed in this protocol do not present any significant risk to either adult or infant volunteers. The information gained from these studies, although not directly beneficial to these individuals, is expected to provide important insights into the commensal relationship that exists between biofilm-forming bacteria and the host. This in turn will contribute to an improved understanding of variables associated with the maintenance of oral health and the initiation of disease.