Anaerobic jar

Anaerobiosis, Anaerobic Jar, construction, working principle, Mechanism, examples of anaerobic organisms, Advantages, diasadvantages

1. ANAEROBIC JAR M.MEENAKSHI, ASSISTANT PROFESSOR, DEPT OF MICROBIOLOGY, SRI RAMAKRISHNA CAS FOR WOMEN

2. MCINTOSH AND FILDES’ ANAEROBIC JAR McIntosh and Fildes ’ anaerobic jar is an instrument used in Microbiology laboratory, for the generation of anaerobic condition ( anaerobiosis ) to culture obligates anaerobes such as Clostridium spp. Anaerobiosis obtained by McIntosh and Fildes ’ anaerobic jar is one of the excellent and most widely used method for anaerobiosis but it requires costly special apparatus and vacuum pump. Availability of gas supply is another major drawback of this system. Currently, it is being replaced by more convenient GasPak system.

3. METHODS OF ANAEROBIOSIS

4. ANAEROBIC JAR

5. DESCRIPTION McIntosh and Fildes ’ jar consists of a 8*5 inch (20*12.5 cm) jar of stout glass or metal with a tight fitting metal lid . The lid can be clamped airtight with a screw and is fitted with two tubes with taps, one for  introduction of gas inside (inlet)  and the other as  outlet  for vacuum valve. The lid also contains  two terminals  that can be connected to an  electric supply A capsule containing alumina pellets coated with palladium ( palladinished alumina) is suspended under the lid by stout wires which are connected with the terminals to  heat the catalyst The Catalyst active at room temperature is also available.

6. PRINCIPLE McIntosh and Fildes ’ anaerobic jar works on the principle of evacuation and replacement, where the air inside the chamber is evacuated and replaced with mixture of gases (consisting of 5%CO2, 10%H2 and 85%N2) . It is practically impossible to evacuate all the air so some amount of oxygen will still be left behind. The residual oxygen left behind is converted to water using Spongy palladium or platinum catalyst. The catalyst acts as a catalyzing agent causing slow combination of hydrogen and oxygen to form water. Reduced methylene blue is generally used as indicator (mixture of NaOH , methylene blue, and glucose). It becomes colorless anaerobically but regains blue color on exposure to oxygen.

7. PROCEDURE  Keep the inoculated culture plates inside the jar along with an indicator. Screw tight the lid Close the inlet tube and connect outlet tube to a vacuum pump ( at least three quarters of the air of the jar can be removed). Note the pressure on a vacuum gauze and when the pressure is reduced to 100 mm Hg (i.e., 600 mm below atmospheric), tightly close the outlet tap. Connect the inlet tap is to a hydrogen supply and then open it. Hydrogen is passed through a small wash bottle. Bring the reduced pressure up to 760 mm Hg (i.e., atmospheric) by monitoring on the vacuum gauze as 0. Switch on the electric terminals for heating the palladinised crystal  (When room temperature catalyst is used heating is not required ). The catalyst helps the combination of hydrogen and residual oxygen to form water. This process is allowed to continue for 20 minutes. Incubate the McIntosh and Fildes ’ jar in an incubator at 37°C for 48 hours.

8. MONITORING EFFICACY OF ANAEROBIOSIS : Reduced methylene blue indicator is used to check the efficacy of anaerobiasis . A tube containing reduced methylene blue solution had to kept inside the jar along with the culture plates. Methylene blue is colorless in reduced conditions and turns blue when oxidized.

9. ADVANTAGES McIntosh and Filde's anaerobic jar  is an instrument used in the production of an anaerobic environment Examples of anaerobic organisms include: Actinomyces . Clostridium. Propionibacterium. Bifidobacterium. Bacteroides . Fusobacterium. Prevotella .

10. DISADVANTAGES Anaerobic jars can be prone to leaks and therefore may not always provide strictly anaerobic conditions . They also require a large volume of incubator space and become expensive to operate in laboratories with a high anaerobic workload. Most importantly, culture plates in anaerobic jars cannot be inspected during incubation without interrupting the anaerobic conditions. This results in a loss of bacterial viability if plates need to be re-incubated or when subcultures need to be made for further investigation.