Table of Contents
- What is an Incubator?
- Components/Parts of Incubator
- Principle/ Working of Incubator
- Procedure for running an incubator
- Types of incubators
- Uses of Incubator
- Precautions
What is an Incubator?
- In microbiology, an incubator is an insulated, enclosed device designed to provide optimal conditions of temperature, humidity, and other environmental factors necessary for organism growth.
- An incubator is essential laboratory equipment for cultivating microorganisms under controlled artificial conditions.
- An incubator can be used to culture both unicellular and multicellular organisms.
Components/Parts of Incubator
Cabinet
- The cabinet is the primary structure of the incubator, featuring a double-walled cuboidal enclosure with a capacity ranging from 20 to 800L.
- The outer wall is constructed from stainless steel sheets, while the inner wall is made of aluminum.
- The space between the two walls is filled with glass wool to insulate the incubator.
- This insulation prevents heat loss and reduces electricity consumption, ensuring the efficient operation of the device.
- The inner wall of the incubator has inward projections to support the shelves inside.
Door
- Each incubator has a door to seal the insulated cabinet.
- The door itself is insulated and features a glass window to allow observation of the incubator's interior without disturbing the environment.
- A handle on the door facilitates easy opening and closing.
Control Panel
- Located on the outer wall of the incubator, the control panel includes all switches and indicators necessary to control the incubator’s parameters.
- The control panel also features a switch to regulate the device's thermostat.
Thermostat
- The thermostat is used to set the desired temperature of the incubator.
- Once the set temperature is reached, the thermostat automatically maintains it until a new temperature is set.
Perforated shelves
- The inner wall supports perforated shelves where culture media plates are placed.
- The perforations allow hot air to circulate throughout the incubator.
- In some models, the shelves are removable for easy cleaning.
Asbestos door gasket
- The asbestos door gasket creates an almost airtight seal between the door and the cabinet.
- This seal prevents external air from entering, maintaining an isolated hot environment inside the cabinet.
L-shaped thermometer
- A thermometer is placed on the top of the outer wall of the incubator.
- One end of the thermometer, marked with gradations, remains outside for easy temperature reading, while the other end, containing the mercury bulb, slightly protrudes into the chamber.
HEPA filters
- Advanced incubators may include HEPA filters to minimize contamination from airflow.
- An air pump with filters creates a closed-loop system, reducing the risk of contamination within the incubator.
Humidity and gas control
- CO2 incubators have a reservoir beneath the chamber that contains water to maintain relative humidity by vaporization.
- These incubators also include gas chambers to control the concentration of CO2 inside the incubator.
Principle/ Working of Incubator
- An incubator operates on the principle that microorganisms require specific parameters for growth and development.
- The core concept of incubators is that microorganisms will grow and multiply when provided with optimal conditions of temperature, humidity, oxygen, and carbon dioxide levels.
- Inside an incubator, the thermostat maintains a constant temperature, which can be monitored externally via a thermometer.
- The temperature is regulated through heating and non-heating cycles.
- During the heating cycle, the thermostat heats the incubator, and during the non-heating cycle, the heating stops, allowing the incubator to cool by radiating heat to the surroundings.
- Insulation from external conditions creates an isolated environment inside the cabinet, promoting effective microbial growth.
- Other parameters, such as humidity and airflow, are maintained through various mechanisms that simulate the natural environment of the microorganisms.
- Adjustments are also provided to control the concentration of CO2, which helps balance the pH and humidity needed for microbial growth.
- Variations of the incubator, such as shaking incubators, are available. These provide continuous movement of cultures, essential for cell aeration and solubility studies.
Procedure for running an incubator
Once the cultures of organisms are prepared, the culture plates are placed inside an incubator at the desired temperature for the required period. In most clinical laboratories, the usual temperature for bacteria is 35–37°C.
The following steps should be followed when operating an incubator:
- Before using the incubator, ensure no leftover items from previous cycles are inside. If the same incubator is used for multiple organisms that require identical parameters, they can be placed together.
- Close the incubator door and switch it on. Heat the incubator to the desired temperature for the specific organism. Use the thermometer to verify the temperature.
- If the organism requires a specific concentration of CO2 or humidity, set those parameters accordingly.
- Once all parameters are set, place the Petri dish cultures on the perforated shelves upside down, with the media on top. This prevents condensation from collecting on the medium's surface, which can inhibit the formation of isolated colonies.
- If the Petri dish cultures need to be incubated for several days, seal the plates with adhesive tape or place them in plastic bags or food containers.
- Finally, lock the door and keep the plates inside for the required incubation time before removing them.
Types of incubators
Incubators can be categorized based on their specific parameters or purposes:
Benchtop incubators
- The most common type of incubator used in laboratories.
- These incubators feature basic temperature control and insulation.
CO2 incubators
- Special incubators with automatic control of CO2 and humidity.
- Used for cultivating bacteria that require 5-10% CO2 concentration.
- Humidity is controlled by placing water beneath the incubator's cabinet.
Cooled incubators
- Designed for incubation at temperatures below ambient levels.
- Equipped with modified refrigeration systems for both heating and cooling controls.
- Heating and cooling controls must be appropriately balanced in these incubators.
Shaker incubator
- Thermostatically controlled incubators that provide agitation.
- Advantageous for rapid and uniform heat transfer to culture vessels and increased aeration, which accelerates growth.
- Suitable only for broth or liquid culture media.
Portable incubator
- Smaller in size and used for fieldwork, such as environmental microbiology and water examination.
Uses of Incubator
Incubators are utilized in various fields, including cell culture, pharmaceutical studies, hematological studies, and biochemical studies. Some of the specific uses of incubators are:
- Growing microbial cultures or cell cultures.
- Maintaining cultures of organisms for future use.
- Increasing the growth rate of organisms that have a prolonged growth rate in natural environments.
- Reproducing microbial colonies for the subsequent determination of biochemical oxygen demand.
- Breeding insects and hatching eggs in zoological studies.
- Providing controlled conditions for sample storage before laboratory processing.
Precautions
The following precautions should be observed when operating an incubator:
- To avoid temperature fluctuations that can affect microorganisms, refrain from repeatedly opening the incubator door.
- Ensure that all required growth parameters for the organism are met before placing culture plates inside the incubator.
- Place the plates upside down with the lid at the bottom to prevent water condensation on the media.
- Regularly clean the inside of the incubator to prevent organisms from settling on the shelves or in the corners.
- When using the incubator for an extended period, place sterile water underneath the shelves to prevent the culture media from drying out.
