Cocci - spherical bacteria, with the diameter of 0.2-4,5 microns. The group cocci are streptococci, staphylococci, mikrokocchi, diplococci, Neisseria, sarcina. Cocci are different reciprocal location of individual cells (Fig.). Streptococci form chains, diplococci are arranged in pairs, micrococci form clusters of irregular shape, sartini - accumulation of cubic form. Cocci can have ovate or lanceolate form (pneumococcus). Some cocci resemble coffee bean (gonorrhea). The group cocci combines purely saprophytic and parasitic forms.

The shape and location kokkov:
1 - Streptococcus pyogenes (pathogenic), dominated by spherical cells;
2 - Streptococcus faecalis (Laboratorny)dominate oval cells;
3 - Diplococcus pneumoniae (the causative agent of lobar pneumonia), the cells of conical shape, surrounded by a capsule;
4 Neisseria gonorrhoeae (exciter gonorrhoea), the cells in the form of coffee beans are arranged in pairs;
5 - Gaffkya, groups of tetrad;
6 - sarcina, clusters cubic form;
7 - Staphylococcus aureus (the causative agent of purulent processes), clusters of irregular shape;
8 - Staphylococcus zymogenes, chaotic accumulation of irregular shape.

Biochemical activity cocci decreases with increasing adaptation to parasitic existence. Staphylococcus and Streptococcus spp fermented carbohydrates, allocate proteolytic enzymes, forming indole; pneumococci have only charolettekirme activity, enzymatic activity meningokokkov gonokokkov and insignificant. The need for power change in reverse order: Staphylococcus grow in simple environments, Streptococcus - on mediums with carbohydrates, pneumococci and meningococci - on serum and blood environments, gonorrhea - on environments with ascitic fluid. Cocci produce exotoxins (Staphylococcus), hemolysins (Staphylococcus and Streptococcus spp), fibrinolizin and hyaluronidase (staphylococci, streptococci, pnevmokocchi), endotoxins (pneumococci, meningococci, gonokocchi).
Pathogenic cocci cause mattery-inflammatory diseases of the skin, mucous membranes, and connective tissue, sore throat and endocarditis, septicemia, septicopyemia, food intoxication and other Many cocci conditionally pathogenic. Separate groups cocci - see Staphylococci, Streptococci, Enterococci. Cm. also Bacteria.