Question

1.What does Streptococci look like under the microscope?

a.strings of rods

b.strings/chains of spheres

c.clusters of rods

d.grape-like clusters of spheres

2.What is the total magnification when you used he 40X objective?

a.400X

b.40X

c.4X

d.4000X

QUESTION 3

1. What was the purpose of the streak plate method?

	a.	to count the number of bacteria in a culture
	b.	to count the number of coliforms in a culture
	c.	To isolate single colonies from a mixture of bacteria
	d.	to show that bacteria are everywhere

QUESTION 4

1. The dye that gives Gram+ bacteria their color is

	a.	crystal violet
	b.	safranin
	c.	Iodine
	d.	methylene blue

1. The dye that is retained by Gram- bacteria is

	a.	iodine
	b.	Methylene blue
	c.	Safranin
	d.	Crystal violet

QUESTION 6

1. The counterstain used for the acid fast staining procedure is

	a.	carbolfuschin
	b.	crystal violet
	c.	methylene blue
	d.	safranin

QUESTION 7

1. Which of the following is NOT a selective medium?

	a.	Blood agar
	b.	Mannitol salt
	c.	BGB
	d.	Snyder's agar

QUESTION 8

1. Alpha hemolysis is

	a.	The complete lysis of red blood cells
	b.	The complete lysis of bacteria
	c.	The partial lysis of red blood cells
	d.	No lysis of red blood cells

QUESTION 9

1. Amylase is an enzyme which breaks down

	a.	gelatin
	b.	starch
	c.	lactose
	d.	glucose

QUESTION 10

1. A medium that supports the growth of a wide variety of bacteria

	a.	synthetic medium
	b.	selective medium
	c.	nutrient medium
	d.	differential medium

Answer 1

1. (B) string/chain or spheres- streptococci appears as a chain or pair of round, ovoid or generally spherical in shape.

2. (A) 400X - The total magnification is calculated by multiplying magnification of objective lens with 10X i.e. ocular lens.

3. (C) to isolate single colonies from mixture of bacteria- The streak plate method is utilised in microbiological experiments for isolating the pure cultures from mixed bacterial cultures. Single pure colonies are isolated via streak plate method.

4. (A) crystal violet- The gram positive bacteria are stained purple as it retains the crystal violet dye in thick peoptidoglycan layer of bacterial cell wall.

5. (C) safranin- The gram negative bacteria appears pink as the thin peotidoglycan layer washes out the primary crystal violet stain however, on addition of ethanol and staining with safranin it retains the counter stain safranin.

6. (C) methylene blue- the methylene blue dye os used as counter stain in acid fast staining. The decolorized cells takes up the methylene blue and appears blue whereas the acid fast cells retains the red colour.

7. (A) blood agar- blood agar is an enriched medium that provides extra nutritional supplements for microbes.

8. (C) partial lysis of red blood cells- it is a greenish discoloration that represents partial decomposition of Jb of RBC.

9. (B) starch- Amylase is a digestive enzyme that primarily breaks down complex starch molecules.

10. (C) nutrient medium- a general nutrient media can support the growth of wide range of bacteria. The common nutrient media is the nutrient agar that allows the cultivation and isolation of variety of bacterial organisms.