Atlas of Cultivation of Anaerobes—Anaerobic Jar, ultivation of Anaerobes—Anaerobic Jar, A Photographic Atlas for the Microbiology Laboratory
Purpose
Cultivation of obligate anaerobes and microaerophiles requires providing an environment in which oxygen is either absent or considerably reduced. Various methods have been devised to provide these environments, three of which are covered in the remainder of Section 3.
The anaerobic jar (Figure 3-40) is used to grow obligate anaerobes and microaerophiles. Because it is the atmosphere within the jar that is anaerobic, the jar can be incubated in a normal incubator alongside aerobically grown cultures.
Principle
Inoculated plates or tubes are placed in the jar and the appropriate gas-generating sachet is activated. In the case of the AnaerogenTM Gas Generating System by Oxoid, simply opening the packet inside the jar and immediately clamping the lid on the jar is all that is necessary. Ascorbic acid in the packet reacts with free oxygen and in turn releases CO2. Within 30 minutes, the atmosphere inside the jar is less than 1% O2 and between 9 and 13% CO2. A methylene blue (or some other) indicator strip is also placed inside the jar. It will turn blue if exposed to air, thus acting as a control to ensure anaerobic conditions have been produced. Figure 3-41 shows two plates inoculated with the same organisms, but one was incubated anaerobically while the other was incubated aerobically.
The Oxoid CampygenTM sachet works in a similar way, but produces 5% O2, 10% CO2, and 85%
N2. It is designed for growing microaerophiles, such as Campylobacter jejuni.
3-40 THE ANAEROBIC JAR
Note the sachet and the white indicator strip inside the jar. The
sachet has performed properly, reducing the oxygen level within
the jar to less than 1%, as evidenced by the indicator strip. If
the indicator were blue, it would mean free oxygen remained in
the jar and the resulting growth would be in question relative to
its ability to survive in anaerobic conditions.
3-41 PLATES INCUBATED INSIDE AND OUTSIDE THE ANAEROBIC JAR
Both Nutrient Agar plates were inoculated with Staphylococcus aureus (top),
Pseudomonas aeruginosa (right), and Clostridium sporogenes (left). The plate
on the left was incubated aerobically outside the jar; the plate on the right was
incubated inside the anaerobic jar. Note the relative amounts of growth of the
three organisms.
Suggested Reading
- Michael J. Leboffe & Burton E. Pierce. A Photographic Atlas for the Microbiology Laboratory 4th edition 2011
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