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What Is Agar?

Agar is a type of sugar in a gelatinous form made from algae and typically used to grow bacteria in lab. Bacteria eat the agar and help scientists perform culture tests.

Agar is one of those materials that can be found in science laboratories. It is, in fact, one of the most distinctive of those materials mostly because of its unique smell. But what is agar? The best way to define agar is by talking about its chemical makeup. Agar is a polymer that is composed of subunits of galactose sugar.

According to the Biology-Online Dictionary:

Agar (noun): a gelatininous material derived from algae, specifically used as a culture medium of bacteria and other cells for diagnostic or laboratory experiments purposes.

The agar that we find in science laboratories has been dissolved first in boiling water and then cooled. That is why it looks gelatinous.

How Do We Obtain Agar? 

Agar is obtained from red algae in California or in different parts of East Asia. Agar is a component of the cell wall of those algae.

“Happiness and bacteria have one thing in common; they multiply by dividing!” — Rutvik Oza

But laboratory agar is not found in nature in the same state it is used in a science lab. First, it needs to be given its gelatinous texture but going through the process we have explained (boiled and then cooled).

What Is Agar Used For? 

Actually, agar is used for many different purposes. Its main purpose is to work as a culture medium for several different microorganisms (chiefly, bacteria).

But agar has other, more every day uses. For example, did you know that agar is also used in order to thicken ready-made sauce or soup? Well, it is. And it is also used in the manufacturing of different beverages, ice cream, and jelly; and, beyond the food industry, also in fabrics and cosmetics.

The reason why agar is used so widely is that, unlike good old gelatin, it can be used to culture bacteria. The problem with gelatin is that is can be degraded by bacteria. In other words, bacteria can eat gelatin but it cannot eat agar.

“Bacteria: the only culture some people have.” — Hesiod

But that is not the only reason why agar is preferable to regular gelatin. Agar is also used because is bother stronger and firmer than gelatin.

Having said all that, gelatin is still used for culturing bacteria when agar is not available.

What Kind of Agar Are There?

There are several types of agar available. Each of them has its own characteristics. Some of them are suitable for student use, while others should just be used by professional scientists mostly because there is a risk of contamination from them.

“Bacteria keeps us from heaven and puts us there.” — Martin H. Fischer

View Comments

  • Actually agar is not eaten by bacteria it simply provides gel base. Agar itself is a component added to the media that is not digested or effected by the microbes. That's what we have been taught atleast.