Definition

Noun: A solid, gel-like substance used in laboratories to grow microorganisms such as bacteria and fungi. It is made by combining a nutrient broth with agar, a gelatinous material derived from seaweed, which solidifies the mixture to provide a stable surface for microbial growth.

Usage

"Nutrient agar" is a compound noun. It refers specifically to the prepared, solidified growth medium. It is typically used as a mass noun (e.g., "poured nutrient agar") but can be counted when referring to specific plates or batches (e.g., "prepare three nutrient agars").

Examples

• The microbiologist sterilized the nutrient agar before pouring it into Petri dishes.
• This bacterium forms distinctive yellow colonies on nutrient agar.
• We need to check if the sample grows on standard nutrient agar.

Advanced Usage

• Selective/Differential Media: While basic nutrient agar supports the growth of many microorganisms, the term is often the base for more specific media. For example, "blood agar" is nutrient agar supplemented with blood.
• In Research Protocols: Instructions often specify "on nutrient agar" to describe the standard solid medium for routine cultivation, as opposed to liquid "nutrient broth."

Variants and Related Words

• Agar (noun): The gelling agent itself, derived from red algae.
• Nutrient broth (noun): The liquid form of the growth medium without the agar solidifying agent.
• Culture medium (noun): The general term for any substance used to support microbial growth; nutrient agar is a type of solid culture medium.
• Plate (noun, in lab context): Often used informally to refer to a Petri dish containing nutrient agar (e.g., "streak the plate").

Synonyms

• Growth medium (general synonym)
• Agar medium (broader synonym, as other agars exist, e.g., Sabouraud agar)
• Solid medium (descriptive synonym contrasting with liquid broth)

Related Phrases/Idioms

No common idioms or phrasal verbs are associated with this specific technical term.

Noun

1. any culture medium that uses agar as the gelling agent