MCB 3020 Lecture Notes - Lecture 2: Gram Staining, Mycobacterium Tuberculosis, Mycobacterium
Document Summary
Step 2: dyes and simple staining: dyes. Make internal and external structures of cell more visible by increasing contrast with background. Methylene blue, basic fuchsin, crystal violet, safranin, malachite green. Have positively charged groups; bind to negatively charged molecules such as nucleic acids, many proteins, and the surfaces of bacterial and archaeal cells. Possess groups such as carboxyls (-cooh) and phenolic hydroxyls (-oh) In their ionized form, have a negative charge and bind to positively charged cell structures: dyes. Acid dyes have negative charges: simple stains. Use can determine size, shape, and arrangement of bacteria: differential staining. Divides microorganisms into groups based on their staining properties. Differential stain used to detect presence or absence of structures. Divides bacteria into two groups, gram-positive and gram-negative, based on differences in cell wall structure: acid-fast staining. Particularly useful for staining members of the genus mycobacterium.
