Summary
Nutrient mixtures, liquid or agar, designed to grow microorganisms in the laboratory.
In depth
Nutrient agar and broth provide carbon, nitrogen, minerals and growth factors. Minimal media contain only essentials and test auxotrophs. Agar, from red algae, is solid at room temperature but melts at 85 °C.
Complex media have undefined ingredients; defined media have known composition. Incubation conditions (temperature, oxygen) matter. Anaerobes need special jars.
Example: nutrient agar supports many non-fussy bacteria.
Media can be liquid (broth), solid (agar plates, slopes) or semi-solid. Defined (synthetic) media have known chemical composition, while complex media use extracts (yeast extract, peptone) with undefined composition. Enriched media such as blood agar support fastidious organisms, and anaerobic culture needs reducing agents or gas jars. Robert Koch introduced solid media, and Fanny Hesse suggested agar.
Agar is not digested by most bacteria, melts at about 85 degrees and sets at about 40 degrees. Plates are incubated upside down to prevent condensation dripping onto colonies. Pure cultures are obtained by streaking for single colonies.
Example: blood agar shows haemolysis around Streptococcus colonies, a clue to the species.
Frequently asked questions
What is Culture Media?
Nutrient mixtures, liquid or agar, designed to grow microorganisms in the laboratory.
Which area of biology covers Culture Media, and how advanced is it?
Culture Media is one of the 54 topics in Microbiology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Microorganisms, Selective and Differential Media, Fermentation.
Can you give an example of Culture Media?
Blood agar shows haemolysis patterns of Streptococcus.
What should I learn before Culture Media?
Work through the Beginner topics in Microbiology first, such as Microorganisms, Bacteria, Archaea, then return to Culture Media. Intermediate topics assume the Beginner vocabulary.
What topics are related to Culture Media?
The closest topics to Culture Media are Microorganisms, Selective and Differential Media, Fermentation, Algae. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Culture Media?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Culture Media. To practise the whole of Microbiology, use the Microbiology quiz.
How is Culture Media different from Microorganisms?
Culture Media: Nutrient mixtures, liquid or agar, designed to grow microorganisms in the laboratory. Microorganisms: Living things too small to see without a microscope, including bacteria, archaea, protists, fungi and microscopic algae. Read both side by side and note what each one explains.
How should I study Culture Media step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Microorganisms and explain the difference aloud. Finally, take the Microbiology quiz and come back to this page for any question you miss.