Microbiology Lab Practical 1

Question 0

What ingredient is added to nutrient broth to make it solidify?

Answer 0

Agar

Question 1

Resolving power

Answer 1

Ability to completely separate two objects in a microscopic field.

D=lambda divided by NA
D is limit of resolution
Lambda is wavelength used to observe specimen
NA is numerical aperture

Question 2

What temp. And pressure are things autoclaved?

Answer 2

121degrees Celsius
15min
15 psi of steam pressure

Question 3

What temp does agar melt?

Answer 3

100 degrees Celsius

Question 4

What temp does agar solidify?

Answer 4

45 degrees Celsius

Question 5

Why are plates incubated upside down

Answer 5

Because if they aren’t then condensation from the dish lid will be deposited on the agar surface, allowing organisms to swim and preventing the formation of individual colonies

Question 6

When would you use a negative stain?

Answer 6

When studying morphology of bacterial cells and characterizing some of the external structures, such as capsules, that are associated with bacterial cells

Useful for accurately determining cell dimensions

Useful for observing spirochaetes, which tend to be very thin cells that do not readily stain with pos

Question 7

What dye do you use for neg staining and is it neutral, acidic, or basic

Answer 7

Nigrosin

Acidic

Question 8

Three basic dyes/stains

Answer 8

Methylene blue
Basic fuchsin
Crystal violet

Question 9

One acidic dye

Answer 9

Eosin

Question 10

Types of cocci

Answer 10

Diplococci and tetrads

Streptococci

Staphylococci

Question 11

Types of Rods(bacillus)

Answer 11

Coccobacillus

Bacilli

Fusiform

Question 12

Simple stain definition

Answer 12

Use of a single stain to color a bacterial cell

Question 13

Why are slides heat fixed prior to staining? 2reasons

Answer 13

1. Cause them to adhere to slide

2. Preserve the structural integrity of the cells

Question 14

Reagents used in a capsule stain

Answer 14

Congo red

Manevals stain

Question 15

How to calculate the scale of a drawing

Answer 15

Scale= drawing size/ actual size

Question 16

Types of molecules that may be found in a capsule

Answer 16

glycocalyx

Poly-D-glutamic.

Question 17

Difference between gram pos and neg

Answer 17

Pos- purple

Neg- pink

Question 18

Stains used during gram staining lab and what they do

Answer 18

Crystal violet- primary stain

Grams iodine- mordant. Combines with crystal violet to form insoluble complex with pos.

Alcohol or acetone- decolorization. Pos will retain purple, but dye mordant is removed from neg leaving it colorless.

Safranin- counterstain. Colors gram neg. pink/ red

Question 19

Gram pos cell wall vs gram neg cell wall

Answer 19

Pos- thick peptidoglycan. Little phospholipid membrane inside

Neg- outer membrane, peptidoglycan, then phospholipid membrane

Question 20

Gram pos bacterium

Answer 20

Staphylococcus epidermidis

Question 21

Gram neg bacterium

Answer 21

Pseudomonas fluorescens

Question 22

Who do bacteria form spores?

Answer 22

It allows them to survive environmental conditions that are not favorable for growth

Question 23

Name a genus of a spore forming bacterium

Answer 23

Bacillus

Question 24

Reagents of schaeffer Fulton spore stain

Answer 24

Malachite green

Safranin

Question 25

Reagents in acid stain fast

Answer 25

Basic-fuchsin

Acid-alcohol

Methylene blue

Question 26

Purpose of acid fast stain

Answer 26

It is a diagnostic tool

Question 27

Name one acid fast bacterium

Answer 27

Tuberculosis