Maintaining biological specimens such as microorganisms, cells or eggs under controlled conditions of temperature, humidity, gas composition and time to promote growth, replication or biochemical reactions.
Explanation
Incubation is a core procedure in microbiology and cell biology. After inoculation, samples are placed in an incubator that maintains a defined environment appropriate for the organism or process being studied. Temperature settings are chosen to approximate the optimal growth range of the organism; for example, human pathogens are often incubated at 35–37 °C. Other parameters such as humidity and carbon dioxide concentration are adjusted to mimic natural conditions—mammalian cell cultures require 5 % CO2 to maintain physiological pH in bicarbonate-buffered media. The length of incubation depends on the generation time of the microorganism or the kinetics of the biochemical reaction. Automated incubators may include shaking or agitation to enhance aeration and mixing. Incubation not only supports microbial growth but also underlies assays like enzyme-linked immunosorbent assays, where antigen‑antibody reactions are allowed to occur under controlled conditions, and polymerase chain reaction thermal cycles that alternate between defined temperatures. Failure to maintain the proper environment can lead to inaccurate results or contamination.
Examples and practices
Clinical laboratories incubate throat swab cultures on blood agar plates at body temperature for 24–48 hours to detect group A streptococci. Mammalian cell lines, such as HeLa cells, are grown in humidified incubators at 37 °C with 5 % CO2 to support metabolism and proliferation. ELISA tests require incubating plates with patient sera and conjugated antibodies to allow specific binding before washing and detection. Developmental biologists incubate fertilised chicken eggs under controlled temperatures to study embryogenesis. Many PCR protocols include an initial denaturation step followed by cycles of annealing and extension, each at specific temperatures and times, effectively controlling a series of incubations at different temperatures.
Maintaining precise environmental conditions during incubation ensures reproducible growth and reaction kinetics. Adjusting parameters to match the biology of the organism or assay is critical for obtaining reliable data and interpreting results.
Related Terms: Incubation Period, Incubator, In Vitro, Microbiology, Culture