tpyes of differential staining
gram stain, acid-fast stain, capsule
the purose of the gram stain is to
differentiate between gram positive and gram negative bacteria
thick cell wall of peptidoglycan, stain purple or blue, more pathogenic,hidden, cocci or spiral shaped
thin cell wall, stains pink or red, outer lipopolysaccharide (LPS) membrane or lipid A, rod shaped
order of gram stain procedure
1.bacterial smear prep-transfer colony to slide w/H20
2.Primary stain with crystal violet-binds to cell wall
3.gently rinse with distilled water
4.add Gram's iodine for 1 min to fix violet to cell wall
5.gently rise with distilled water
6.wash with decolorizer until runoff is clear
(if gram positive will retain crystal violet, if gram negative will lose primary stain and apprar colorless)
7.add secondary safranin for 1 min(if gram negative will appear red)
higher afffinity for the primary stain(carbol fuchsin) and resistance to decolorization by an acid alcohol solution- a lipid soluble penetrating the waxy cell wall. ex. tuberculosis. mycobacteria cell walls contain a waxy substance composed of mucolic acids.
won't stain the cell but stains everything else. capsule will appear clear. known as indirect staining.
basic stain-cell proper
capsule-remains unstained-white halo
the resting or dormant stage of an endospore. resists u.v., gamma rays, desiccation.
the active or feeding stage of an endospore
is not a stain but a mordant, It doesn't give color, it fixed the violet stain to the cell wall.
dormant, tough nonreproductive structure produced by small number of bacteria
primary function is to ensure survival for bacterium through periods of environmental stress/
low permeability makes them hard to stain.