Fig. 5.

Diagram illustrating scenarios possible between a growing root and bacteria relatively immobile in the soil. Bacteria are depicted as dark dots; the root tip is shown at three stages relative to the bacteria. (A) Scenario 1: the root tip grows past the bacterium. (B) Scenario 2: the bacterium anchors to the root cap and is carried forward with the tip as it extends (see also Fig. 6). The root cap mucilage is shown as a dark line in (A), suggesting how it covers the root in hard soil, and is shown as a light line in (B), suggesting how it covers the root tip in loose soil (see text for details and additional explanation). (C) Scenario 3: the bacterium swims to maintain its position on a particular root developmental zone.