An anaerobic jar is a rigid, sealable container used to create an oxygen‑free atmosphere for the incubation of microbial cultures on plates or in small tubes. It allows laboratories to grow obligate anaerobes without needing a full anaerobic workstation.
Principle and operation
The typical anaerobic jar consists of a heavy glass or plastic vessel with a clamped lid that seals tightly. Inside, plates or tubes are placed on a rack, and an oxygen‑absorbing system is activated. Commercial GasPak systems use sachets that, when water is added, generate hydrogen and carbon dioxide; a palladium catalyst embedded in the lid catalyses the reaction of hydrogen with residual oxygen to form water, reducing the oxygen concentration to below 0.1 %. Some jars instead use prefilled gas packs that release a defined mixture of nitrogen, carbon dioxide and hydrogen. An anaerobic indicator strip containing methylene blue or resazurin is placed in the jar to verify that oxygen has been removed. After sealing, the jar is incubated at the desired temperature; anaerobic conditions are typically reached within an hour and maintained as long as the catalyst and gas generation are effective. Because no external gas supply is required, anaerobic jars are simple and portable compared with glove boxes, but they cannot be opened without re‑exposing contents to air.
Uses and limitations
Anaerobic jars are widely used in clinical and teaching laboratories to culture obligate anaerobic bacteria such as Bacteroides species, Peptostreptococcus, Fusobacterium and Clostridium perfringens on solid media. They are also suitable for culturing microaerophiles or capnophiles by using gas mixes with reduced but not zero oxygen. The jars allow small numbers of plates to be incubated at low cost and are useful for antibiotic susceptibility testing under anaerobic conditions. However, jars are not designed for manipulations; once sealed, plates cannot be examined or subcultured without breaking the anaerobic environment, so sequential operations require multiple jars. GasPak generators can produce moisture and heat that may affect sensitive media, and palladium catalysts must be dried and regenerated periodically to remain effective. For large‑scale cultivation or experiments requiring continuous manipulation, anaerobic chambers or glove boxes are preferred.
Anaerobic jars provide a convenient way to establish an oxygen‑free environment for short‑term incubation of anaerobic and microaerophilic cultures. Their simplicity and low cost make them staples in microbiology laboratories.
Related Terms: Anaerobic chamber, GasPak, Obligate anaerobe, Anaerobic culture, Reducing media