Here from two genera of algae, Gelidium and

Here we will look at what agar is, what it is used for, and generally why it is important. Agar resembles gelatin and in most cases is very similar to it.

What Is Agar?

Agar, which looks similar to Jello, is derived from red/purple algae. It utilizes two polysaccharides (sugars) called agarose and agaropectin found in the cell walls of certain algae.

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They can be extracted from the alage through boiling. Again, it looks similar to Jello and has a similar texture and feel to it, albeit a little bit slimier.

Where Is It Found?

The red algae that are used to produce the agar are from Pacific coastal regions of Asia and California. The specific algae are from the Gelidium and Gracilaria genera.

Agar can essentially be found anywhere from kitchens to laboratories. We will go into greater detail next as to where and why it would be found in these places.

What Is It Used For?

Agar is commonly used in the laboratory to help feed and grow bacteria and other microorganisms. It acts as a culture that provides nutrients and a place for these items to grow, but since it is indigestible to the microorganisms, they cannot eat and destroy it. There are various types of agar, some of which include MacConkey Agar, Chocolate Agar, Tryptic Soy Agar, Triple Sugar Iron Agar, Hektoan Agar, and Mannitol Salt Agar.

Various strains of bacteria growing on agar plates
Bacteria growing on agar plates

Agar is also found in things like jelly, make-up, and clarifying agents for drinks.

Agar can also be used a substitute for gelatin for those who are vegetarians and want to stay away from animal products.

How Is Agar Important?

As you skim through the uses of agar, I think it becomes apparent. It is an ingredient in some foods, cosmetics, and drinks. Where it really shines is as a medium for bacteria and microorganism cultures. Without agar, we would have greater difficulty in growing and studying bacteria. ‘So what?’ you might say. Well it is because of our studying of bacteria that we came up with medicines such as antibiotics.

By understanding what these microorganisms are capable of, we can understand better how less complex organisms live and thrive. By understanding the building blocks of life, we better understand our own selves.

Agar plate with bacteria colonies
Agar plate

Lesson Summary

Agar is:1) Made from red/purple algae2) Made up of two sugars, agarose and agaropectin3) Primarily from two genera of algae, Gelidium and Gracilaria4) Used in studying and creating cultures of microorganisms5) Also used in some foods in place of gelatin


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