Princeton University researchers discovered that the bacteria Vibrio cholerae keeps food generated by the community's productive members away from those of their kind that attempt to live on others' leftovers. The bacteria use two mechanisms that are likely common among bacteria. In some instances, the natural flow of fluids over the surface of bacterial communities can wash away excess food before the freeloaders can indulge. In microscope images, shiftless V. cholerae (red) were in abundance under conditions of no fluid flow (left image). When the bacteria were grown in an environment with fluid flow -- similar to that found in nature -- cooperative V. cholerae (yellow) won out (right image).