An optical microscope is commonly used to observe its size, and a micrometer can also be used to measure its size under a microscope.

diplococci

Streptococcus

staphylococcus

Tetragenococcus

Sarcina

coccobacillus

Mycobacteria

Category: Vibrio, spirillum, campylobacter

Influencing factors: temperature, pH value, medium composition and culture time

The osmotic pressure of Gram-positive bacteria is as high as 2026.5~2533.1kPa (20~25 atmospheres)

The osmotic pressure of Gram-negative bacteria is 506.6~608.0kPa (5~6 atmospheres)

Main ingredients: peptidoglycan

Functions: ① Maintain cell shape; ② Inhibit mechanical and osmotic damage (the cell wall of Gram-positive bacteria can withstand a pressure of 20kg/cm²); ③ Mediate cell-to-cell interactions (invasion of the host); ④ Prevent macromolecule invasion; ⑤ Assists cell movement and division; ⑥ It has antigenicity and can stimulate the body’s immune response

Defective type (L-type bacteria)

The main function

intermediary

Main components: ribosomes, storage products, various enzymes and intermediate metabolites, various nutrients and monomers of macromolecules

microstructure

Chemical composition: polypeptide or polysaccharide

Functions: ① Anti-phagocytosis: The capsule can effectively resist phagocytosis by host phagocytes due to its hydrophilicity, space-occupying and barrier effects; ② Adhesion: Capsular polysaccharides can cause bacteria to adhere to each other and to The surface of tissue cells or inanimate objects is an important factor causing infection; ③ Resistance to damage by harmful substances: The capsule is the outermost layer of bacterial cells, which can effectively protect the bacteria from or be less susceptible to a variety of bactericidal and bacteriostatic substances. Damage; ④ Anti-desiccation effect: Capsular polysaccharides are highly hydrated molecules with a water content of more than 95%, which can help bacteria resist the threat of dryness to survival; ⑤ When there is a lack of nutrients, the capsule can be used as a carbon source and energy source, which is beneficial The capsule can also serve as a nitrogen source

Chemical composition: protein, called flagellin; highly immunogenic, called flagellar antigen

Role: Flagellar antigens can be used to identify bacteria or classify bacteria

Ordinary pili: spread on the surface of the bacterial body, the number can reach hundreds or more, very thin; have adhesion effect

Sexual pili; found only in a few Gram-negative bacteria; as genetic material

Concept: The cytoplasm of certain bacteria is dehydrated and concentrated under certain conditions, forming round or oval bodies with multi-layered membranes and low permeability inside the bacteria.

Reasons for strong resistance: ① The spores have a multi-layered dense thick film structure, which is difficult for physical and chemical factors to penetrate; ② The moisture content of the spores is low (about 40%), and the protein is not easily denatured after being heated; ③ The core and cortex of the spores contain a large amount of Picolidinedicarboxylic acid, which combines with calcium to form salts that can improve the thermal stability of various enzymes in spores

The most effective way to kill spores: high-pressure steam sterilization

Single dyeing method

Counterstaining