Colonies of Microorganisms

visible clusters of cells (bacteria, yeast fungi) or mycelia (mold fungi) of a single species of microorganism, formed when the organisms reproduce or grow on a solid substrate. Colonies are flat or convex formations on the surface of a solid nutrient medium. Colonies of microorganisms are obtained under laboratory conditions by inoculating meat-infusion agar or other media with the microorganisms. The colonies may be large or small, smooth or wrinkled, and glossy or matte. The edges may be smooth or scalloped. The color may be grayish; when there has been pigment formation, the colony may be various shades of yellow, orange, red, or other colors. Colonies of mold fungi are covered with a downy coating. The colony’s characteristics (shape, color, and so forth) are usually used in a description of the species. Under natural conditions, colonies of microorganisms may arise on the surface of food products, in soil, and at the bottom of bodies of water.