From Big Medical Encyclopedia

COLONY BACTERIAL — the isolated accumulation of microbic cells formed of one cell which bred on a surface or in the thickness of a dense medium (artificial or on natural nutritious substrate). Outward To. it is characteristic of certain groups of bacteria though can vary depending on culture conditions (Wednesdays, temperatures, density of crops, time of growth etc.). Growth To. occurs radially: old cells remain in the center, young people develop on the periphery that is connected with receipt from the environment of nutrients. Pirt (S. J. Pirt, 1975) considers that the speed of specific growth of colonies depends on extreme concentration of nutrients and can be calculated mathematically. The sizes of colonies vary within 0,05 mm — 8 cm at different types. Some bacteria form the pigments painting colonies in certain colors (yellow, red, orange, etc.). The form K depends on a way of cell fission. At incomplete division of a cell keep protoplasmic bridges and are located with uneven chains, forming To. irregular shape, anthracis, characteristic, e.g., for V., and R-form of entero-bacteria. At full division the stood apart cells are located with the sliding ranks that causes formation smooth To. By method of scanning submicroscopy (see) reveal the structure of a surface of bacteria and their relative positioning defining a form K.

Fig. 1. Scheme of various types of a structure of colonies: and — types of an eminence of colonies over the surface of nutrient medium (1 — flat, 2 — slightly convex, 3 — raised, 4 — convex, 5 — convex hilly, 6 — convex folded, 7 — raised with the concave middle, 8 — raised with the acting center, 9 — dome-shaped); — a form of edge of colonies (1 — equal, 2 — gear, 3 — jagged, 4 — wavy, 5 — lobular, 6 — ciliate, 7 — fringed, 8 — fragmentary, 9 — branched out); in — internal structure of colonies (1 — transparent, 2 — translucent, 3 — opaque, 4 — homogeneous, 5 — slightly granular, 6 — coarse-grained, 7 — lokonoobrazny, 8 — fibrous, 9 — treelike).
Fig. 2. Colonies of the dissociating strain of Sh. flexneri: 1 — a smooth form (x 30); 2 — a rough form (X 15).

The main criteria To. (height over the level of the environment, a form of edge, density and internal structure) are schematically presented in the figure 1. Besides, determine the size (diameter, in mm), character of a surface (opaque, brilliant, smooth, ischerchenny), coloring at the reflected and transmitted light (color, fluorescence, opalescence, a luminescence), a consistence (oily, viscous, kroshkovaty) and differentiation (a difference in the center and for the periphery for density, I blossom, etc.). Bacteria of a certain look create typical To., what is used at release of pure growths at primary stage of identification. Colonies of some types are so characteristic that have diagnostic value (see. Identification of microbes ). The crowding forms a protea grow in a type of the creeping-away plaque, transparent on the periphery of colony, V. anthracis form the fancy curls reminding the head of a jellyfish, Sh. sonnei II of a phase grow in a type of a grape leaf, and young colonies of Y. pestis remind the crumpled lacy scarf. To. are visible with the naked eye, but study them at increase (X 30,X 40); at the same time the surface is better looked through in slantwise the passing beam of light. Many bacteria form smooth forms of colonies (fig. 2, 1), Bacteria of some types are capable to form mutant forms of colonies — rough (fig. 2, 2), mucous, dwarfish, and also transitional forms of colonies.

See also Bacterial culture , Dissociation of bacteria .

Bibliography: Perth S. D. Bases of cultivation of microorganisms and cells, the lane with English, M., 1978; T and m and to about in V. D. Microbiology, M., 1973; Carpenter P. L. Microbiology, Philadelphia, 1972; Manual of clinical microbiology, ed. by E. H. Lennette a. o., Washington, 1974; Salle A. J. Fundamental principles of bacteriology, N. Y., 1973; Wilson G. S. a. Miles A. A. Topley and Wilson’s principles of bacteriology and immunity, v. 1—2, L., 1964.

H. A. Homenko.