(A) A thin biofilm composed of small clusters of cells from each bacterial taxon.
(B) A thicker biofilm showing expansion of the facultative anaerobe Rothia and the beginnings of expansion of anaerobes Veillonella and Actinomyces.
(C) A mature structure showing well-defined domains.
(D) Increasing width of a clonal domain toward the perimeter suggests a selective advantage toward the periphery.
(E) Decreasing width toward the perimeter suggests a disadvantage at the periphery or selective advantage in the interior.
(F) Constant width suggests neither selective advantage nor disadvantage with respect to neighboring taxa. See also Figures S2 and S5, Video S3, and Tables S2 and S3.