Coccus. The cocci are spherical or nearly spherical, and the cell diameter is about 65438 0 microns. The new cells produced by cocci division often keep a certain arrangement, which is of great significance in classification and identification. For example, cells that divide along a plane are scattered and exist alone, called micrococcus; Two cocci are arranged in pairs, called diplococcus; A number of cocci are arranged in a chain, which is called streptococcus. If cocci divide according to two perpendicular planes, every four cells will form a field together after division, which is called tetracocci. According to three mutually perpendicular planes, after division, every eight cocci are arranged together to form a cube, which is called octococcus. If the fracture surface is irregular, multiple cocci pile up together in disorder, which is called staphylococcus.
Bacillus (Bacillus). Bacteria are rod-shaped and vary greatly in size, length and thickness. Brevibacterium is close to cocci, and long bacilli are filamentous. Generally, the length of Bacillus is 1 ~ 5 microns, and the width is 0.5 ~ 1.5 microns. Some bacilli are straight, while others are slightly curved. Some ends are truncated, and some are slightly rounded. Most of the bacilli are scattered, but some species are arranged in chains of different lengths, or in a grid, or in a figure-eight adjacent arrangement. The morphology and arrangement of Bacillus also have certain significance in classification and identification.
Spirillum (Spirillum). Bacteria are curved. According to the degree of cell bending and cell hardness, it can be divided into Vibrio, Spirillum and Spirulina. Vibrio slightly bends; Spirillum is tough and spirally curved; The spirochete is soft and curved like a spiral.