Pudding, yokan, cold cakes, when mentioning these foods, I think most people will have happy scenes in their minds, and pink bubbles will float out of their backs. One bite down, the sweet taste, the smooth taste all the time stimulates the brain to accelerate the secretion of dopamine. At the same time, these foods have been loved by people since their invention. And did you know that the ingredients that bring a smooth taste to these foods have also made a huge contribution to our human medical cause?
Brown sugar cold cake
As a thickener, agar, a substance derived from cauliflower, is not only suitable for traditional foods such as cold cakes and pudding, but also as a carrier to assist the suspension of fruit particles in fruit-grained orange beverages. Agar has long occupied a place in the food industry because of its natural, safe and good coagulation effect. However, agar also shines in the biology lab. If you work in a biology lab, I'm sure you'll have more access to agar than a regular chef. Agar is a common carrier material for solid media, and as long as you need to experiment with the plate method, you must need agar. Morphological identification? Let's paint a Petri dish; isolate the bacteria? Let's paint a flat plate; quantity detection? Let's paint a flat plate. Unlike other ingredients, as a plate-cultured soul, agar dissolves other species in it, eventually forming a smooth "big jelly". This allows the medium to be present in solid form, facilitating subsequent tests.
Plate culture of microorganisms
Why does agar change change the world? This starts with the significant contribution of the plate culture method to the development of microbiology. Let's go back to the end of the 19th century, when people, thanks to Pasteur's research, just realized that many diseases were caused by pathogenic microorganisms. Therefore, researchers at that time devoted themselves to isolating microorganisms for research. However, the method used at the time was liquid culture, which dissolved nutrients in water and then inoculated bacteria, which was simple and easy. However, there is a problem that it is difficult to isolate pure bacteria. Usually, when the medium changes from clear to turbid, the culture can be considered successful, but we cannot know whether the microorganisms inside are the same microorganism. Of course, scientists of that era were deeply troubled by this and invented the liquid separation method, which gradually diluted the liquid to obtain pure cultured bacteria. However, due to the low efficiency of this method, the study cycle is greatly extended.
But in 1881, in the laboratory of Mr. Robert Koch, one of the founders of microbiology, an experimenter creatively added agar to the liquid medium, and then the solid plate medium came out. On the plate medium, we only need to add the liquid containing bacteria and apply the liquid evenly to the surface with a coating stick, the whole process is similar to the pancake fruit on the street. Then put the plate into the right temperature, the plaque will grow, so that it is easy to observe the characteristics of these microorganisms and select pure microorganisms. In addition, Koch invented the plate scribing separation method, which separates high concentrations of mixed microorganisms into a single colony by slicing on the plates. Since then, the speed at which scientists have studied pathogenic microorganisms has increased dramatically.
Salmonella monobacterial colonies isolated by plate scribing
If you think the story of agar ends here, you're wrong. With the development of science and technology, we have recognized the regulatory role of nucleic acid substances (DNA and RNA) on organisms, and the means we usually use to isolate nucleic acids is agarose gel electrophoresis. Agarose is a refined product of agar, which can form a gel itself and is stable without affecting the nucleic acid composition. When the agarose solidifies, holes of different sizes form inside, which is the pool needed for electrophoresis. When we are energized, the nucleic acid molecules will advance in the gel pool under the action of electricity, depending on the size of the molecules, these molecules will remain in different positions of the gel, according to the needs of the research, only need to cut the gel in the target area to get the nucleic acid molecules we need.
Gel electrophoresis photo White bands are nucleic acid molecules
From microbial culture to molecular biology, from macro to micro. Agar has played a vital role in our life sciences research and has truly changed the world. I believe that it will continue to contribute to us in the future. Finally, let's tell a little story, legend has it that Koch could not find a suitable coagulation material when making solid medium, Koch's wife knew, took out the agar from the kitchen to make pudding at night and asked him to try, and the experiment was very successful. Since then, Agar has walked from the kitchen into the laboratory.