5Sometimes you can have intermediate shapes that are described by a combination of the three. For example: coccobacilli (rod shaped but mostly round)
6Other terms Prosthecae: starlike appearance Staphylococci: looks like a bunch of grapes.Flagellum: A hair that is whip-like and attached to the bacteria in some way. Most of the time these are used for mobility.
7Staining also helps to classify bacteria Gram stainDeveloped by Danish Physician Dr. Hans Christian Gram in 1884Procedure: Cells are heated, crystal violet is applied, then iodine is added, then alcohol, then red dye.Gram positive cells: These cells retain the purple dye and mask the red.Gram negative cells: These cells appear red.
8What does it mean?Different bacteria have a different composition in their cell walls, therefore you can classify the bacteria by how they stain based on their cell wall composition.
10Acid Fast StainingThis procedure is taking a red dye which is applied while the bacteria is being heated, then a fast acting acid is added to decolorize the cells.Only a few cells will retain their red color under these conditions because they have a specific lipid in their cell wall. (Mycolic acid)
11Most acid-fast bacteria are of the genus Mycobacterium Examples of diseases that Mycobacteium cause are: tuberculosis and leprosy.Note: These bacteria do not stain well with the Gram stains so acid-fast stains need to be used.
12Other ways to classify bacteria By their DNA or RNA (Genetic information)By their metabolism or how they regulate their basic functions. (nutritional requirements, oxygen requirements, temperature and pH)We will get into Metabolism and Genetics later.