Magnification is an important principle in anaerobic microbiology. Anaerobic bacteria are too small for direct examination with the naked eye. Light microscopes and electron microscopes magnify specimens sufficiently, so they can be seen. A special light microscope, called a phase contrast microscope, enables microbiologists to see living specimens in some detail.
Microbiologists must kill and stain anaerobic bacteria to study the finer details. Dyes, such as methylene blue, stain specimens for examination with a light microscope. A dye called basic fuchsin effectively stains anaerobic bacteria. For viewing with an electron microscope, staining with heavy metals, such as osmium, accentuates surface details.
Different types of anaerobic bacteria react differently to dyes. For this reason, microbiologists use various differential staining methods to assist them in the identification of unknown specimens. For example, the Gram stain test applies crystal violet or methylene blue to unknown bacteria and washes the specimen with a solvent. Gram-positive bacteria retain their purple color after application of the solvent, while Gram-negative bacteria lose it. The application of safranin, or basic fuchsin, imparts a reddish stain to the gram negative bacteria, according to Penn Medicine.
Microbiologists grow cultures of anaerobic bacteria to study the strengths and weaknesses of pathogens and to facilitate the identification of unknown bacteria. They must take care not to expose the bacteria to oxygen, especially when preparing a culture of obligate anaerobes. They used pre-reduced media to grow the cultures and place the medium, inoculated with bacteria, into an oxygen-free environment, such as an anaerobic jar or a special chamber from which the oxygen has been removed. Medium refers to the nutrient broth in which the bacteria grow. Pre-reduced means oxygen has been chemically removed from the components of the medium.