Basic Microbiology laboratory for upper division college students with color diagrams and very simple instructions. The manual covers lab safety, how to use a microscope, aseptic transfer of bacteria, simple, gram, capsule, acid fast, spore, and negative staining, environmental requirements of bacteria, antibiotic susceptibility testing, bacterial control methods, membrane filtration, standard plate count, plaque assay, biochemical tests for the identification of pathogenic Enterobacteriaceae.
Lab 2: Aseptic TechniqueYou will be working with many pathogenic species of bacteria in the laboratory. Remember that bacteria are in the air as well as on the skin, the counter, and all objects and equipment that have not been sterilized. The most important tool for transferring cultures is the wire inoculating needle or loop. It can be quickly sterilized by heating it to red hot in a Bunsen burner flame. Lab 3: Simple, Negative, and Gram StainThe Gram stain is the most important and universally used staining technique in the bacteriology laboratory. It is used to distinguish between gram (+) and gram (-) bacteria. Lab 4: Acid-Fast, Spores, and Capsule StainsAcid-fast stain is a differential stain used to identify acid-fast organisms such as members of the genus Mycobacterium. Acid-fast organisms are characterized by wax-like, nearly impermeable cell walls; they contain mycolic acid and large amounts of fatty acids, waxes, and complex lipids. Lab 6: Antibiotic Susceptibility TestingIn microbiology, McFarland standards are used as a reference to produce solutions that contain approximately similar numbers of bacteria for use in standardized microbial testing (Kirby Bauer). This is done by matching the turbidity (cloudiness) of McFarland standard with that of the test solution. Lab 8: Membrane FiltrationMembrane filtration is a technique for testing water samples. In this procedure, water is drawn through a special porous membrane designed to trap microorganisms larger than 0.45 μm. Afterward, the filter is applied to the surface of Endo agar plates and incubated for 24 hours. Endo agar is a selective media that encourages gram-negative bacterial growth and inhibits gram-positive growth. It also contains lactose for fermentation and a dye to indicate pH changes.