Figure 1. Three-dimensional reconstructions of buccal cells invaded by large numbers of cocci. (A) A cluster of buccal cells that contained cells invaded to various degrees by bacteria labeled by both the green Streptococcus-specific and red universal probes (shown in yellow), as well as bacteria recognized only by the universal probe (shown in red). The cell denoted by the arrow had been extensively invaded by streptococci. (B) Z-plane slices of three-dimensional reconstructions were generated to confirm that bacteria seen were intracellular. This slice of the reconstruction shown in panel A contained intracellular streptococci, as denoted by the arrows. (C) A buccal cell dominated by presumed streptococci that were labeled by the universal probe (red). This sample also was treated with the F. nucleatum-specific probe, and the buccal cell shown contained several yellow F. nucleatum cells (arrows) in close association with cocci. (D) A z-plane slice of the buccal cell shown in panel C, indicating that intracellular F. nucleatum were in association with intracellular cocci.