A culture is a population of microorganisms or cells grown under controlled conditions in a nutrient medium.
Explanation
In microbiology and cell biology, culture refers both to the process of cultivating living cells and to the collection of organisms or cells that result from growth. To establish a culture, a sample of bacteria, fungi, yeast or mammalian cells is introduced into a sterile medium that supplies necessary nutrients, water, and an environment suitable for reproduction. The medium may be liquid (broth) or solidified with a gelling agent such as agar. Early solid media used gelatin, but gelatin melted at body temperature and was digested by many bacteria; Robert Koch adopted agar at the suggestion of Fanny Hesse because it solidifies between 32 and 42°C, melts at 85°C, and resists digestion.
Cultures allow researchers to isolate, identify and study microorganisms in pure form. They can be classified as batch cultures, continuous cultures, pure cultures or mixed cultures depending on the method and composition. Environmental factors such as temperature, pH and oxygen availability influence growth; most bacteria prefer near-neutral pH, although acidophiles and alkaliphiles have broader ranges. In clinical settings, cultures are used to diagnose infections and test antimicrobial susceptibility. In biotechnology and industry, cell cultures produce antibiotics, vaccines, enzymes and recombinant proteins. Proper aseptic technique and sterile equipment are essential to avoid contamination and ensure reliable results.
Types and Key Points
- Liquid (broth) cultures support uniform growth and are used for large-scale biomass production and biochemical assays.
- Solid media, prepared with agar, allow isolation of individual colonies and assessment of colony morphology.
- Batch cultures grow cells in a closed system with fixed nutrients, while continuous cultures maintain steady-state growth by adding fresh medium and removing spent medium.
- Pure cultures contain a single species; mixed cultures contain multiple species and more closely resemble natural communities.
- Environmental parameters such as temperature, pH and aeration must be optimized for each organism or cell type.
Culturing is a fundamental technique in microbiology and cell biology. It enables the study of organism physiology, genetics and metabolism and supports applications ranging from clinical diagnostics to industrial production.
Related Terms: Agar, Pure Culture, Broth, Sterile Technique, Inoculation