BIOL 3340 Chapter 2 Microscopy Fixation l preserves

BIOL 3340

Chapter 2 Microscopy

Fixation l preserves internal and external structures and fixes them in position l organisms usually killed and firmly attached to microscope slide l heat fixation – routine use with procaryotes l preserves structures overall morphology but not internal l chemical fixation – used with larger, more delicate organisms l protects fine cellular substructure and morphology

Light Microscopy

Dyes and Simple Staining Dyes make internal and external structures of cell more visible by increasing contrast with background l have two common features l l divides microorganisms into groups based on their staining properties e. g. , Gram stain l e. g. , acid-fast stain l

Gram Staining l most widely used differential staining procedure l divides bacteria into two groups based on differences in cell wall structure

Acid-fast Staining Acid Fast Staining: • particularly useful for staining members of the genus Mycobacterium e. g. , Mycobacterium tuberculosis – causes tuberculosis e. g. , Mycobacterium leprae – causes leprosy • high lipid content (mycolic acids) in cell walls is responsible for their staining characteristics

Gram-negative Cell Walls and Acid Fast cell wall in Chapter 3

Bibliography l http: //en. wikipedia. org/wiki/Scientific_method l https: //files. kennesaw. edu/faculty/jhendrix/bio 3340/home. html l Lecture Power. Points Prescott’s Principles of Microbiology-Mc Graw Hill Co.