Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Time series of flow pattern during hole formation. (Top panel) At 
random initial conditions produce a small flow. (Middle panel) At 
the bacteria have started to aggregate in three locations. At these locations there is a strong downward flow. In locations where there are fewer bacteria, the return flow dominates the flow produced by the bacteria, setting up circular flow patterns. (Bottom panel) Flow at 
Scaling of arrows in top panel is larger to make the arrows more visible.
