Agar

Description

Agar (also known as agar-agar) is a gelatinous substance derived from red algae, particularly Gelidium and Gracilaria species. It is a polysaccharide composed of agarose and agaropectin. Agar is commonly used in laboratory settings as a solidifying agent for culture media and in various biochemical applications. It is odorless, tasteless, and forms a gel when dissolved in hot water and cooled. Agar remains solid at room temperature, making it an ideal material for culturing microorganisms.

Common Uses in a Biology Lab

• Microbial Growth Media: Agar is primarily used as a solidifying agent in agar plates, which are used to culture bacteria, fungi, and other microorganisms. Nutrient agar or specialized media containing agar provides a stable surface for bacterial growth, facilitating the isolation and identification of microbial species. 
  • Common Media: Examples include LB agar (Luria-Bertani agar), MacConkey agar, and Sabouraud agar. These are used to grow specific types of bacteria or fungi.
• Cell Culture: Agar is also used in cell culture applications to create agarose gels for cell separation. The gel helps in 3D cell cultures or provides a stable substrate for cell attachment.
• Gel Electrophoresis: Agarose, a component of agar, is used to prepare agarose gels for gel electrophoresis in molecular biology. These gels are commonly used to separate DNA, RNA, or proteins based on their size and charge during electrophoresis.
• Embryo Culture: In some biological research, agar is used to culture embryos, especially in marine biology or developmental biology research.
• Immobilization of Enzymes and Cells: Agar is sometimes used as a matrix for immobilizing enzymes or cells for biotechnological applications. It can help maintain stability and increase efficiency in enzyme reactions or cell-based assays.
• Cytotoxicity Assays: Agar is used in agar diffusion tests for evaluating the toxicity of substances to microorganisms or cells, helping to determine the safety and biological effects of various compounds.

Safety Hazards

• General Safety: Agar itself is generally considered non-toxic and safe to handle. However, caution should still be exercised when preparing media or handling agar plates, especially when using potentially harmful microorganisms or chemical reagents in conjunction with agar.
• Inhalation of Aerosols: When preparing or working with agar plates in a dry state (e.g., during media preparation or cleaning), inhaling dust or spores could be harmful, especially if pathogenic microorganisms are involved.
• Microbial Contamination: Agar plates can become contaminated with harmful microorganisms, so proper sterilization (autoclaving) and careful handling are necessary to avoid exposure to pathogens.
• Heat: When preparing agar media, high temperatures are used to dissolve the agar. Caution should be taken to avoid burns when handling hot agar solutions.

Handling

• PPE (Personal Protective Equipment): Wear gloves, safety goggles, and a lab coat when working with agar plates or preparing agar media to avoid contamination and exposure to any biological materials.
• Sterilization: Agar is typically sterilized by autoclaving to prevent microbial contamination. Ensure proper sterilization procedures are followed when preparing media or reusing agar plates.
• Storage: Agar plates or agar media should be stored in a sterile environment, typically in an incubator or fridge depending on the microbial culture requirements. Agar should be kept sealed to prevent contamination and dehydration.
• Disposal: Used agar plates containing biological samples should be disposed of as biohazardous waste. They should not be thrown in general waste unless they have been properly disinfected (e.g., by autoclaving).