Can eyes see bacteria

Bacteria are extremely small microorganisms that cannot be seen by the naked eye. There are many types of bacteria, including both beneficial bacteria and harmful bacteria. Some bacteria are important causes of human diseases, such as plague, tuberculosis, forest disease, etc. The forms of bacteria are also diverse. If you want to see bacteria, you need to use a microscope and conduct bacterial culture.

The discovery of bacteria

Bacteria were first discovered by the Dutchman Antonie van Leeuwemhoek (1632-1723) on the dental plaque of an old man who had never brushed his teeth, but people at that time believed that bacteria were naturally occurring. It was not until later that Pasteur pointed out through the gooseneck flask experiment that bacteria were produced by bacteria already in the air, rather than being produced on their own. He then invented the "pasteurization method" and was later hailed as the "Father of Microbiology" [1].

The term "bacteria" was first proposed by German scientist Christian Gottfried Ehrenberg (1795-1876) in 1828 to refer to a certain type of bacteria. The word comes from the Greek βακτηριον, meaning "little stick".

In 1866, German zoologist Ernst Haeckel (1834-1919) suggested the use of "protists" to include all single-celled organisms (bacteria, algae, fungi and protozoa).

In 1878, French surgeon Charles Emmanuel Sedillot (1804-1883) coined the term "microbe" to describe bacterial cells or more generally, microscopic organisms.

Because bacteria are single-celled microorganisms, they cannot be seen with the naked eye and need to be observed under a microscope. In 1683, Antonie van Leeuwenhoek (1632-1723) first observed bacteria using a single-lens microscope of his own design, which magnified the image about 200 times. Louis Pasteur (1822-1895) and Robert Koch (1843-1910) showed that bacteria can cause disease.

The shape of bacteria

(1) Cocci:

Cocci are bacteria that are spherical or elliptical in appearance, with a diameter of 0.5 to 1 micron. There are several types: ① Monococci: exist alone, such as Micrococcus ureabilis; ② Diplococci: such as Streptococcus pneumoniae; ③ Streptococci: such as Lactococcus; ④ Tetracocci: the four cells formed are arranged together to form a field shape, such as Tetracoccus; ⑤ Sarcina: such as Urea sporogenes Sarcina; ⑥ Staphylococci: such as Staphylococcus aureus.

(2) Bacillus:

Bacteria with a rod-shaped appearance are called bacilli, which often include short rods or coccus-shaped bacteria with similar length and width, such as Methano-brevibacter; rod-shaped or long rod-shaped bacteria with a large difference in length and width, such as Bacillus subtilis and Bacterium fusiformis; branched or forked bacteria, such as Bifidobacterium; bamboo-shaped (with both ends truncated), such as Bacillus anthracis, etc.

Depending on the arrangement of bacillus cells, there are paired diplococci, chain-like streptobacilli, and many other shapes, such as palisade-shaped, "eight"-shaped, and filamentous shapes wrapped in a sheath. Typical bacilli include Escherichia coli, Bacillus subtilis, Streptobacillus, and Proteus

(3) Spiral:

Spiral-shaped bacteria are called spirochetes, which are generally 5 to 50 microns long and 0.5 to 5 microns wide. They can be divided into the following categories based on the curvature of the bacteria: ① Vibrio: those with less than one spiral ring are banana-shaped or comma-shaped, such as Vibrio cholerae; ② Spirillum: small, hard spiral bacteria with 2 to 6 full rings, such as Spirillum minor; ③ Spirochaeta: spiral bacteria with many rotations (usually more than 6 rings), long and soft bodies, such as Treponema pallidum.