Which solidifying agent is commonly used to prepare solid bacterial media in microbiology laboratories?

• A. Cellulose
• B. Gelatin
• C. Agar
• D. Starch

Answer: (C)

Verified step by step guidance

1. Understand that solid bacterial media require a solidifying agent that remains stable at incubation temperatures and is not degraded by bacterial enzymes.
2. Review the properties of each option: Cellulose is a structural polysaccharide not commonly used as a solidifying agent in microbiology media.
3. Gelatin can solidify media but is often degraded by bacterial proteases and melts at incubation temperatures, making it less ideal.
4. Agar is a polysaccharide derived from red algae that solidifies media, remains solid at incubation temperatures, and is generally not metabolized by bacteria, making it the preferred choice.
5. Starch is a carbohydrate that can be used in media for specific tests but is not used as a solidifying agent due to its solubility and bacterial degradation.