ABSTRACT
Sagittal sections showed that the pure culture biofilm was diffuse with a thickness of approximately 5 |xm throughout the experiment [Figure 1(g), (h), (i), Figure 2(d)]. In contrast, the mixed culture biofilm was initially more compact, with a higher cell density at the attachment surface. On day 21, saggittal sections revealed an irregular and diffuse biofilm with a dissem i nated foundation and vertical development in the form of outcrops o f cells up to 15 jxm, projecting perpendicularly into the bulk aqueous phase (Fig ure 1). The biofilm thickness developed from 5 jjim on day 7 to 13 |jim on day 21. Horizontal sectioning o f the mixed culture biofilm showed that the anti-isolate PF polyclonal antibody fully penetrated the 5-to 15-jxm-thick layers and labeled cells evenly at all depths o f the biofilm. Isolate PF cells dominated throughout the experiment in the mixed culture biofilm. Isolate AT cells always comprised the smaller fraction of the total cellular mate rial at all developmental stages [Figure 1(d), (e), (f)]. The cell density of isolate AT was higher in the pure culture biofilm compared with its density in the mixed culture biofilm [Figure l(a )-(f)] . The difference was most pro nounced on day 21: only a few isolate AT cells were seen in the mixed cul ture biofilm, whereas the pure culture biofilm was densely populated [Fig ure 1(c), (f)].
