Clinical Bacteriology; Exam 1 review
fully solved
What are the components of the gram stain? - correct answer ✔✔Peptidoglycan
Found in all bacteria except mycoplasma
Gram positive have a higher concentration that Gram negative
Hydrolyzed by lysosome which causes lysis
Mycolic acids
Composed of long branched beta-hydroxyl acids; water insoluble
Resistant to penetration; acid fast staining properties in sufficient quantities
Found in mycobacteria and Nocardia
Techoic acid
Only in gram positive bacteria
Major surface antigens when present
LPS
Endotoxin; only in gram negative bacteria; released upon death
Lipid + polysaccharide
Gram staining - correct answer ✔✔Differentiates between Gram positive bacteria (blue or purple) and
Gram negative bacteria (red or pink)
Colonies of cells are mixed with a crystal violet dye (primary stain), allowed to sit with a binding agent
(Grams Iodine), washed with a decolorizer (alcohol), and stained with a secondary stain (safranin)
Gram positive bacteria have a thicker band of peptidoglycan which has a high affinity for crystal violet so
it holds onto the dye and is not easily washed out; it retains the blue color of the dye, and remains blue
or purple
fully solved
What are the components of the gram stain? - correct answer ✔✔Peptidoglycan
Found in all bacteria except mycoplasma
Gram positive have a higher concentration that Gram negative
Hydrolyzed by lysosome which causes lysis
Mycolic acids
Composed of long branched beta-hydroxyl acids; water insoluble
Resistant to penetration; acid fast staining properties in sufficient quantities
Found in mycobacteria and Nocardia
Techoic acid
Only in gram positive bacteria
Major surface antigens when present
LPS
Endotoxin; only in gram negative bacteria; released upon death
Lipid + polysaccharide
Gram staining - correct answer ✔✔Differentiates between Gram positive bacteria (blue or purple) and
Gram negative bacteria (red or pink)
Colonies of cells are mixed with a crystal violet dye (primary stain), allowed to sit with a binding agent
(Grams Iodine), washed with a decolorizer (alcohol), and stained with a secondary stain (safranin)
Gram positive bacteria have a thicker band of peptidoglycan which has a high affinity for crystal violet so
it holds onto the dye and is not easily washed out; it retains the blue color of the dye, and remains blue
or purple
