FIG. 2.

Various features of single-cellular and clumped growth of the two strains. (A) Growth of nonaggregated wild-type and cps mutant K. pneumoniae strains grown under 250 rpm to prevent any aggregation, as measured by turbidimetry. (Inset) Total cellular protein. No significant differences were seen, and up until the 3-h time point at which subsequent experiments were performed, the growth curves were essentially identical. (B, C, and D) Distribution of bacterial nearest-neighbor distances. For each cell within each biofilm or aggregate studied, the distance to its closest neighboring cell (in micrometers) was determined. Results were pooled across all samples of a given experimental condition (e.g., wild-type aggregates grown at 50 rpm). Comparisons between distributions were made using the Cramér von Mises test for distribution equivalence. Regardless of the hydrodynamic conditions under which they formed, wild-type aggregates demonstrated broader distributions of internal interbacterial distances than mutant flocs. (E) Reconstructions of representative floc and biofilm volumes. Margins of flocs are irregular as the entire volume of these structures was captured whereas only cubic samples were taken of larger biofilms. In each case, individual rods are one micrometer in length.