Techniques in Anaerobic Microbiology

Abstract

The knowledge accumulated in a scientific subject is restricted by advances in experimental technique. Our information concerning the strict anaerobes has been severely limited by inadequate methods of sampling and culturing. Only in the past 30 years, and particularly the last 15 years, has sufficient attention been paid to ensuring that optimum conditions are used to isolate and study the strict anaerobes from a variety of habitats: that is, to providing a laboratory environment devoid of oxygen and with the correct nutrients. Although it was appreciated that for satisfactory growth anaerobes required an environment of low E_h and no oxygen, it was less apparent that many anaerobes required zero oxygen conditions for sampling, transfer and subculture. Hence, the commonly used anaerobic jar incubation technique combined with standard microbiological methods of medium preparation, fluid and colony transfer, were inadequate for all anaerobes with high sensitivity to oxygen. Handling of endospore-forming Clostridia was successful because the endospores were resistant to oxygen and remained viable during aerobic subculturing, provided that anaerobic conditions were maintained for the incubation period. At present two types of techniques are used in anaerobic microbiology: firstly, the method in which all precautions are taken to ensure that oxygen is excluded from every step of the handling procedure, including sample taking, media preparation, transfer and incubation; secondly, a technique where only the incubation step is maintained oxygen-free.