microbiology

Question 1

what are the shapes of bacteria?

Answer 1

• cocci (round shaped)
• bracilli (rod-shaped)
• spirilli (spiral shaped)

Question 2

what determines the shape of bacteria?

Answer 2

the rigid cell wall which has a unique structure

Question 3

what is the bacterial cell wall composed of?

Answer 3

composed of peptidoglycan
- cross-linking provides a strong, but flexible framework to protect cell contents and cells from lysis

Question 4

what are the properties of gram-positive bacteria?

Answer 4

thicker peptidoglycan walls and the cell walls lack lipopolysaccharide

Question 5

what are the properties of gram-negative bacteria?

Answer 5

thinner cell walls (less peptidoglycan) and supplemented by large molecules of lipopolysaccharide

Question 6

what are the staining characteristics of gram-positive bacteria?

Answer 6

retain crystal violet stain/iodine complex = purple (after washing with alcohol)
- counterstain with safranin has no effect
- more susceptible to antibiotics and lysozyme

Question 7

what are the staining characteristics of gram negative bacteria?

Answer 7

do not retain crystal violet/ iodine complex; stained red by counterstain safranin
- not impacted by lysozyme and resistant to penicillin