Virtual knockout of Motility. To achieve a virtual simulated motility knockout, the motility parameter is set to zero, while all other parameters are set to the wild-type values (Table 1). The result is dramatically different from wild-type (compare with Figure 4). Bacterial density pattern is influenced by downstream convection. The washout effect begins to emerge as dominant in comparison to wild-type as the maximum bacterial density decreased one order of magnitude in the knockout simulation. Time points: 1 s, 2 s, 5 s, 10 s, 12 s, 15 s. The bacteria cannot penetrate the mucus layer to colonize before being washed out.