Ultrastructure of colony-like communities of bacteria.

Colony-like communities are poorly studied forms of bacterial growth on agar. These communities are formed after the growth of large amounts of bacteria simultaneously plated onto a limited area of agar, while "classical" colonies are formed as a result of single bacterial cell multiplication. Colony-like communities of Gram-negative and Gram-positive bacteria differ from "classical" microbial colonies in their ultrastructural organization. Almost every cell in colony-like communities has an individual capsule-like envelope (glycocalyx). The cells in these communities are characterized by accelerated ageing. In the course of their development both bacterial colony-like communities and "classical" colonies produce a film, the basic part of which is represented by an elementary membrane. In contrast to "classical" colonies, the thickness of the amorphous layers of this film in colony-like communities did not significantly increase after 24 h of cultivation. The formation of a three-dimensional network of cells in colony-like communities is similar to this process in "classical" colonies. The intercellular matrix of colony-like communities contains numerous membrane vesicles, and has a more amorphous structure and higher electron density than that of "classical" bacterial colonies.