Lab practical 1

Question 1

What is the purpose of aseptic technique?

Answer 1

To prevent contamination during microbial transfer and culture

Question 2

What are the three types of culture media used in pure culture techniques?

Answer 2

Broth, slant, agar

Question 3

What is the purpose of the streak technique?

Answer 3

To isolate pure colonies from a mixed culture

Question 4

What does ‘parfocal’ mean in microscopy?

Answer 4

The ability to keep an object in focus when switching between different objectives

Question 5

What is total magnification?

Answer 5

ocular lens magnification X objective lens magnification

Question 6

Differentiate between bright-field, phase contrast, and dark field microscopy.

Answer 6

Bright-field: standard light, stained, both living & dead
Phase contrast: enhances contrast, living cells, unstained
Dark field: illuminates specimen against a dark background, living cells, unstained

Question 7

What is a common problem in making a smear?

Answer 7

Overheating the slide or using too much sample

Question 8

What is the difference between a simple stain and a differential stain?

Answer 8

-Simple stain uses one dye (highlight the size, shape & arrangement of bacteria ); differential stain uses multiple dyes to differentiate cell types/structures ,(Gram stain, acid fast stain, endospore stain)

Question 9

What are the two types of dyes used in staining?

Answer 9

Acidic and basic dyes

Question 10

What is the significance of cell morphology?

Answer 10

It helps identify the shape and arrangement of cells

Question 11

What reagents are used in the Gram stain?

Answer 11

Crystal violet, iodine, alcohol, safranin

Question 12

What could go wrong during the Gram staining procedure?

Answer 12

Improper timing or washing steps leading to incorrect results

Question 13

How do you interpret Gram reaction?

Answer 13

Gram-positive: purple; Gram-negative: pink

Question 14

What reagents are used in the spore stain?

Answer 14

Malachite green, safranin

Question 15

What is the purpose of the acid-fast stain?

Answer 15

To identify acid-fast bacteria such as Mycobacterium

Question 16

What is the purpose of a capsule stain?

Answer 16

To visualize the capsule surrounding certain bacteria

Question 17

What is the indicator used in TTC motility media?

Answer 17

TTC (2,3,5-triphenyltetrazolium chloride)

Question 18

How can you distinguish between motile and non-motile bacteria?

Answer 18

By observing growth patterns in motility media

Question 19

What is the purpose of a serial dilution?

Answer 19

To reduce the concentration of bacteria for accurate counting

Question 20

What is the function of a Quebec colony counter?

Answer 20

To count bacterial colonies on a plate

Question 21

What is the purpose of the pour plate technique?

Answer 21

To isolate and quantify bacteria in a sample

Question 22

How does UV light affect bacteria?

Answer 22

It causes DNA damage leading to cell death

Question 23

What is the difference between resident and transient flora?

Answer 23

Resident flora are permanent; transient flora are temporary

Question 24

What is measured in the zones of inhibition?

Answer 24

The effectiveness of antibiotics on bacterial growth

Question 25

What are the major structural differences between yeasts and molds?

Answer 25

Yeasts are unicellular; molds are multicellular with hyphae

Question 26

How are protozoa classified?

Answer 26

Based on their movement and reproductive methods

Question 27

Fill in the blank: The major classes of fungi include _______.

Answer 27

[Ascomycetes, Basidiomycetes, Zygomycetes, Chytridiomycetes]

Question 28

what is a broth?

Answer 28

-a liquid medium that supports bacterial growth -grows large # of bacteria, does NOT isolate cultures -no agar agar for fast luxuriant growth

Question 29

what is a slant?

Answer 29

Agar solidified in a tube with a slanted surface store bacterial long term, grow in oxygen-rich areas

Question 30

what is an agar?

Answer 30

-solid medium used in petri dishes, isolating and growing bacteria -solidifying agent (1.5%-2%) for isolation & purification of microbes

Question 31

How to prepare a specimen?

Answer 31

1.) A small amount of water 2.) spread specimen very thinly 3.) Air dry 4.) Pass over flame once to heat fix bacteria ( kill specimen protein coagulation & adherence to slide)

Question 32

what is a basic dye?

Answer 32

positive charge -attracted to slightly neagative surface of the cell ex: crystal violet, safranin, methylene blue, malachite green, carbol fuschin

Question 33

what is an acidic dye?

Answer 33

negative charge -repelled by surface of the cell used to stain area around the cell ex: nigrosine, congo red

Question 34

what is a gram stain?

Answer 34

1.)crystal violet (primary dye-binds with peptidoglycan) 1 min 2.)Grams iodine (mordant) 1 min rinse with water 3.)Aceton-alcohol (decolorizer)=causes it to shrink 10 sec rinse with water 4.)Safranin (counterstain) 1min rinse with water

Question 35

What is an endospore stain?

Answer 35

1.) add paper towel flood with malachite green steam 5 min (primary stain) 2.) rinse with water 3.) Counterstain-safranin 1 min (binds to vegatative cell

Question 36

what is Acid-fast staining?

Answer 36

1.) add paper towel with carbol fuchsin steam. 5 min 2.)remove paper & rinse with water 3.) decolorizer-acid alcohol, 10 sec, rinse with water 3.) counterstain with methylene blue 1min & rinse with water

Question 37

what is a capsule stain

Answer 37

thick polysaccharide layer surrounding the cell -helps attach to surfaces -protects against phagocytes stain background and cell protects being ingested by white blood cells

Question 38

capsule is nonionic

Answer 38

dyes dont bind

Question 39

Streptococcus pneumonia

Answer 39

known for having a prominent capsule that aids in virulence

Question 40

klebsiella & Neisseria

Answer 40

most likely to produce a capsule

Question 41

Dilution factor formula

Answer 41

amount of sample/amount of sample + amount in tube

Question 42

total dilution formula

Answer 42

Tube 1 dilution X Tube 2 dilution

Question 43

how does radiation kill

Answer 43

induces DNA mutations

Question 44

ionizing radiation

Answer 44

(x-ray & gamma-ray) shorter wavelength=stronger effect pulls electrons from DNA

Question 45

UV

Answer 45

-causes thymine dymers -affects the cells ability to replicate DNA -UV-c is the most germicidal but does not penetrate plastic/glass/clothes

Question 46

acidophile

Answer 46

below pH 5

Question 47

acid tolerant

Answer 47

prefer neutral, but can grow in acid

Question 48

neutrophile

Answer 48

6.5-7.5 pH

Question 49

alkalinophile

Answer 49

pH 8+

Question 50

mesophile

Answer 50

20-40 deg C Body 37 deg C pathogen (normal typical microbes)

Question 51

psychrophiles

Answer 51

0-15 deg C die above 20 deg Live in the snow, ice Not pathogenic reason for spoilage in fridge (like the cold)

Question 52

Thermophiles

Answer 52

40 deg + C compost hot springs (very warm)

Question 53

Hyperthermophiles

Answer 53

80-100 deg C Hydrothermal vents (boiling/extremeophiles)

Question 54

what does a larger zone indicate

Answer 54

senstivity/ susceptibility

Question 55

what does it mean when the bacteria is resistent to the antibiotic

Answer 55

bacterial culture shows NO zone of inhibition around an antibiotic disk

Question 56

what is an antibiotic

Answer 56

antimicrobial chemical (made by microbes to kill microbes)