A bacterial culture is a laboratory method for growing bacteria in a controlled environment. It involves placing bacterial cells onto or into a nutrient medium and incubating them under conditions that allow them to multiply. By providing the nutrients and conditions that bacteria need to grow, cultures enable researchers and clinicians to observe colonies, identify species and determine their abundance.
Explanation
Culturing bacteria is a fundamental technique in microbiology. Media can be solid, such as agar plates, or liquid, such as broth. Solid media contain a gelling agent like agar that allows colonies to form on the surface, making it possible to isolate single species by streaking. Liquid media are useful for obtaining large numbers of cells for biochemical tests or further analysis. Different types of media exist: general-purpose media support many non-fastidious species; selective media favour the growth of particular bacteria while inhibiting others; differential media contain indicators that reveal metabolic traits. When a specimen is inoculated and incubated at an appropriate temperature, bacteria divide by binary fission, forming visible colonies. These colonies can be counted to estimate cell numbers or sub-cultured to obtain pure isolates. Cultures are also used to test antibiotic susceptibility, study bacterial physiology and maintain stock strains for research.
Practical uses
In clinical diagnostics, culturing a urine or blood sample can reveal whether a patient has a bacterial infection and which antibiotic may be effective. Food microbiologists culture samples to detect contamination by pathogens such as Salmonella or Listeria. Environmental scientists grow bacteria from soil or water to study microbial diversity and nutrient cycling. By observing colony morphology, colour and haemolysis on media like blood agar, microbiologists gain clues to a bacterium’s identity before performing biochemical or molecular tests.
Culturing remains a cornerstone of bacteriology because it provides a direct way to observe and manipulate living cells. Despite advances in molecular diagnostics, many laboratory investigations still rely on growing bacteria to confirm findings and perform further analyses.
Related Terms: Broth Culture, Blood Agar, Basal medium, Biochemical Tests, Bacterial