Eight-hour-old dental plaque was visualized using confocal scanning laser microscopy. Antibodies against Streptococcus gordonii DL1 and anti-receptor polysaccharides (RPS), commonly found on Streptococcus oralis, were used for indirect immunofluorescence along with the stain Syto 59. At least two staining types are seen within the aggregates: antibody-reactive (anti-DL1 [green], anti-RPS [purple]) cells found in direct association with antibody-unreactive (blue Syto 59–stained) cells. Single colonies containing all three staining types (anti-DL1, anti-RPS, and antibody unreactive) were frequently seen. Reproduced with permission from The Journal of Bacteriology (2).