(1) The size of bacteria Bacteria are tiny, usually measured in microns (μm; 1 μm = 1 / 1000mm). It must be magnified hundreds to thousands of times with a microscope to see it. Generally, the diameter of cocci is about 1μm, the medium-sized bacillus is 2 ~ 3μm long, and the width is 0.3 ~ 0.5μm. Factors such as age and environment have an effect on the size of the bacteria.
(2) Morphology and arrangement of bacteria
Bacteria have three basic forms, namely spherical, rod-shaped and spiral-shaped, respectively called cocci, bacillus and spirillus.
1. Cocci: Cocci are spherical or nearly spherical (such as bean-shaped, kidney-shaped or spear-shaped). The diameter is about 1μm. According to the different planes of bacterial division and the degree of bacterial separation, according to the arrangement of bacterial cells, they are divided into:
(1) Diplococcus: Two bacterial cells are arranged in pairs, such as Neisseria meningitidis, Streptococcus pneumoniae, and Neisseria gonorrhoeae.
(2) Streptococcus: Many bacteria adhere to a chain, such as hemolytic streptococci.
(3) Staphylococcus: many bacteria pile up irregularly like a bunch of grapes, such as Staphylococcus aureus
(4) Tetracoccus and tarcea: 4 cells are arranged in a square, called tetracoccus. The eight bacterial cells adhere to the package and are called serrata.
Bacteria can exist as a single dispersion in specimens and cultures.
2. Bacillus: Bacillus is rod-shaped or ball-shaped. Among the bacteria, there are the most types of bacillus, and their length, size and thickness vary greatly. Large bacilli such as Bacillus anthracis are 3 to 10 μm long, medium ones such as Escherichia coli are 2 to 3 μm long, and small ones are only 0.6 to 1.5 μm long.
Most of the bacilli are scattered, some bacilli can be arranged in a chain, such as Bacillus anthracis; some are branched, such as Mycobacterium tuberculosis; some are in the shape of "eight" or fence, such as Corynebacterium diphtheriae.
3. Spiral bacteria: Spiral bacteria are curved in a spiral shape and can be divided into two categories:
(1) Vibrio: The bacterial body is 2 to 3 μm long, with only one curved, arc-shaped or comma-shaped, such as Vibrio cholerae. In addition to the curved shape, Campylobacter can be seen to be S-shaped or gull-shaped, and the bacterial length is similar to that of Vibrio.
(2) Spirulina and spirochetes: The bacteria are 3 to 6 μm in length, and have several bends, such as S. thermophilus.
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