An incubator is a device used to grow and maintain microbiological cultures or cell cultures. The incubator maintains optimal temperature, humidity, and other conditions such as the carbon dioxide (CO₂) and oxygen content of the atmosphere inside. Incubators are essential for much experimental work in cell biology, microbiology, and molecular biology and are used to culture both bacterial and eukaryotic cells.
Construction and Function
An incubator consists of a chamber with regulated temperature. Some incubators also regulate humidity, gas composition, or ventilation within that chamber. The simplest incubators are insulated boxes with an adjustable heater, typically capable of reaching 60 to 65 °C (140 to 149 °F), though some can go slightly higher (generally no more than 100 °C). The most commonly used temperature for bacteria such as E. coli and for mammalian cells is approximately 37 °C (99 °F), as these organisms grow well under such conditions. For other organisms, such as the budding yeast Saccharomyces cerevisiae, a growth temperature of 30 °C (86 °F) is optimal.
More elaborate incubators can also include the ability to lower the temperature (via refrigeration) or to control humidity or CO₂ levels. This is important in the cultivation of mammalian cells, where relative humidity is typically greater than 80% to prevent evaporation, and a slightly acidic pH is achieved by maintaining a CO₂ level of 5%.
History
The earliest incubators were invented thousands of years ago in ancient Egypt and China, where they were used to keep chicken eggs warm. These were essentially large rooms heated by fires, with attendants turning eggs at regular intervals to ensure even heat distribution.
In the 16th century, Jean Baptiste Porta drew on ancient Egyptian design to create a more modern egg incubator. In the mid-17th century, René-Antoine Ferchault de Réaumur warmed his incubator with a wood stove and monitored its temperature using the Réaumur thermometer, another of his inventions.
In the 19th century, researchers began using incubators for medical advancements. Early laboratory incubators were simply bell jars containing a single lit candle, with cultures placed near the flame on the underside of the jar's lid. Later in that century, the first infant incubator was used at a women's hospital in Paris, heated by kerosene lamps. Fifty years later, Julius H. Hess, an American physician often considered the father of neonatology, designed an electric infant incubator that closely resembles those in use today.
The next major innovation came in the 1960s with the introduction of the CO₂ incubator, driven by the need to identify and study pathogens found in patients' bodily fluids. At this time, incubators also began to be used in genetic engineering, enabling the production of biologically essential proteins such as insulin.
Modern Incubators
Incubators serve a variety of functions in a scientific lab. Many also control humidity. Shaking incubators incorporate movement to mix cultures. Gas incubators regulate the internal gas composition. Some incubators circulate air inside to ensure even distribution of temperatures. Many laboratory incubators have a redundant power source to ensure that power outages do not disrupt experiments. Incubators are made in a variety of sizes, from tabletop models to warm rooms that serve as incubators for large numbers of samples.
