Agar

Agar

1. Definition: Agar is a substance obtained from algae, it has a jelly-like composition and is mainly used as a container for the growth of microorganisms or cells.

2. There are various types of Agar, for example: MacConkey Agar, Mannitol Salt, EMB Agar, Blood Agar.

   • Each type is used for different types of microorganisms and different uses, like distinguishing the types of organisms in the container.

3. Chemical properties: Gel forming capacity, solubility, hidrophobicity, viscosity, stability

4. EMB Media is a selective media used mainly for gram-negative bacteria like Escherichia Coli, though it can also be used for some gram-positive bacteria.

   • Gram-negative bacteria produce acid which turns the colonies dark purple. This is caused by the reaction between the acid and the dyes.
   • Escherichia Coli is a gram-negative type of bacteria primarily found in the lower intestine. It's outer body consists in a cytoplasmic membrane, an outer membrane and a space made of peptide-glucan. E. Coli can resist high pressures and moderately high temperatures.
     • Most types of E. Coli are harmless, although, some varieties of this bacteria may cause food poisoning, diarrhea, or kidney failure. If they are not treated, they could even cause death.
   • EMB Media is made of: Enzymatic Digest of gelatin Lactose: Sugar, Dipotassium Phosphate Eosin Y and Methylene Blue
   • It's main use is for the isolation and differentiation of bacteria.

5. References: Dr. Samuel Porto. (2003). Agar-Agar. 17/09/2017, de AgarGel Sitio web: http://www.agargel.com.br/agar-tec-en.html Tankeshwar Acharya. (2013). Eosin Methylene Blue (EMB) Agar : Composition, uses and colony characteristics. 17/09/2017, de Microbe Online Sitio web: https://microbeonline.com/eosin-methylene-blue-emb-agar-composition-uses-colony-characteristics/ National Institute of Allergy and Infectious Diseases. (15/02/2017). E. Coli Infections. 17/09/2017, de U.S. National Library of Medicine Sitio web: https://medlineplus.gov/ecoliinfections.html Lic. Juan José Canet. (2016). Escherichia Coli: características, patogenicidad y prevención. 18/09/2017, de Betelgeux Sitio web: http://www.betelgeux.es/blog/2016/01/19/escherichia-coli-caracteristicas-patogenicidad-y-prevencion-i/

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