What type of colony margin appears to radiate outward?

The colony margin that appears to radiate outward is referred to as a spreading edge. This characteristic is significant in microbiology as it indicates the growth pattern of certain bacteria on solid media. When observing a colony with a spreading edge, you'll notice that the edges extend outward, creating a broader appearance compared to the center of the colony. This morphology can provide insights into the metabolic activity and motility of the organisms involved.

In contrast, other colony margins do not exhibit this spreading trait; for instance, a filiform margin tends to have smooth and uniform edges without outward extension, while a pulvinate margin appears raised and rounded, and a convex margin is typically rounded but does not necessarily radiate. Understanding these distinctions helps in proper identification and characterization of microbial colonies.