Explain why Gram-positive mycoplasmas appear pink in a Gram-stained smear.

Assume that you are viewing a Gram-stained field of red cocci and blue rods through the microscope. You can safely conclude that you have

a. Made a mistake in staining

b. Two different species

c. Old bacterial cells

d. Young bacterial cells

e. None of the above

Why is it clinically helpful to know the Gram property of an organism?

Indicate the true statements and then correct the false statements so that they are true.

a. The Gram stain is a simple stain.

b. Simple stains reveal information about size, shape, and arrangement.

c. Bright field microscopy requires a stained sample.

d. Dark field microscopy requires a stained sample.

e. The acid-fast stain detects peptidoglycan in the cell walls of certain bacteria.

f. Gram-positive bacteria have a thin peptidoglycan layer in the cell wall.

Select the most accurate statement.

a. The Gram stain is a simple stain.

b. Bacterial endospores appear green from the acid-fast stain.

c. The acid-fast stain is used to detect bacteria that have a capsule.

d. Bacterial flagella can only be seen with electron microscopes.

e. The mordant in the Gram stain is iodine.