WRINKLES IN TIME: Researchers grew a colony of bacteria with Sytox Green, a fluorescent marker that lit up when cells died. As the colony grew, its extracellular matrix restricted the movement of cells, until those cells on the underside of the film began to die. The areas with dead cells (green) experience a release of mechanical pressure imposed by the extracellular matrix, allowing the film to buckle and form the wrinkled surface seen in some bacterial colonies.BIOFILM COURTESY OF SUEL LAB;
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M. Asally et al., “Localized cell death focuses mechanical forces during 3D patterning in a biofilm,” PNAS, 109:18891-96, 2012. Bacteria can form multicellular biofilms, which are glued together by an extracellular matrix. Wrinkles in the film—large enough to see with the naked eye—help to provide protection from penetration by water and gases and appear to help the colony ward off antibiotics. The physical forces shaping these 3-D structures were unknown, but Gürol Süel of the University of California at San Diego and his colleagues now show that localized cell death appears to facilitate the formation of wrinkles. Kenneth Bayles, a professor at the University of Nebraska Medical Center, who was not part of the study, says cell death in bacterial colonies has been underappreciated, and ...
