Written Lab Final Questions

Question 1

what are three important procedures using aseptic technique

Answer 1

transfer with loop
transfer liquid with pipet
isolating pure culture

Question 2

process of preparing a streak plate

Answer 2

protect from contamination
mark bottom of dish
streak with loop of bacteria
flame loop and cool
repeat for 3 sections

Question 3

what is microbiology the study of?

Answer 3

organisms too small to be seen with the naked eye

Question 4

the modern compound light microscope consists of?

Answer 4

two lens systems

Question 5

what is the objective lens?

Answer 5

lens closest to the material on the slide

Question 6

what is the ocular lens?

Answer 6

eyepiece that magnifies the image formed by objective lens

Question 7

how do you find the total magnification?

Answer 7

multiplying eyepiece lens by objective magnification

Question 8

what are the factors that limit resolution of a lens?

Answer 8

angle

wavelength of light entering scope

Question 9

what cannot be seen under a light microscope?

Answer 9

viruses

Question 10

to observe bacteria in a stained or wet mount it is necessary….

Answer 10

to use an oil immersion lens

Question 11

what is the most common way to stain organisms

Answer 11

gram stain

Question 12

what is one of the first procedures employed in identifying organisms?

Answer 12

gram stain

Question 13

what does gram stain do?

Answer 13

reveals:
morphology
arrangement
information of cell wall

Question 14

what do gram positive cell walls have?

Answer 14

thick peptidogylcan

Question 15

what is the procedure for gram stain?

Answer 15

1. put water on slide
2. place organism on slide
3. heat fix
4. flood slide with crystal violet
5. rinse with water
6. iodine
7. water
8. ethanol
9. water
10. safranin
11. water
12. blot

Question 16

why is acid fast useful?

Answer 16

it helps identify bacteria with waxy lipid cell wall

Question 17

what is the function of a capsule?

Answer 17

protect bacterium from WBC engulfment

Question 18

what is the function of the endospore?

Answer 18

protects organisms from heat, chemicals and starvation

Question 19

what is a direct count?

Answer 19

suspension of bacteria is placed on slide that has been ruled into squares

Question 20

what are the methods of enumerating bacteria?

Answer 20

plate count
direct count
turbiditic method

Question 21

what is an example of an obligate aerobe

Answer 21

micrococus luteus

Question 22

what is an example of an obligate anaerobe?

Answer 22

clostridium

Question 23

what is an example of a facultative anaerobe?

Answer 23

e. coli

Question 24

what are some physical methods used to mill microorganisms?

Answer 24

heat and uv light

Question 25

what effect does cold temps have on microbes

Answer 25

inhibit but do not kill

Question 26

what microorganisms produce heat resistant endospores

Answer 26

bacillus and clostridium

Question 27

what is an example of irreversible denaturation?

Answer 27

dehydrating microorganisms

Question 28

what is the typical sterilization time and temps?

Answer 28

2 hours at 165 for dry heat | 15 at 121 for moist heat

Question 29

how does uv light kill microorganisms?

Answer 29

dna mutations

Question 30

what is the actual mechanism of mutation?

Answer 30

formation of thymine dimers

Question 31

what are semi synthetic antibiotics?

Answer 31

chemically modifying naturally made antibiotics

Question 32

what are synthetic antibiotics

Answer 32

completely synthesized in lab

Question 33

what is the kirby bauer test?

Answer 33

test potency of antibiotics and drugs

Question 34

how is susceptibility to a particular antibiotic determined?

Answer 34

measuring diameter of the zone of inhibition

Question 35

what shows a positive coagulase test?

Answer 35

if cells clump together

Question 36

what are the benefits of normal biota?

Answer 36

- prevent harmful organisms from colonizing the skin | - produce enzymes that inhibit nonresident organisms

Question 37

is staphylococcus epidermidis coagulase positive or negative?

Answer 37

negative

Question 38

is staphylococcus epiddermidis mannitol positive or negative?

Answer 38

negative

Question 39

what is the outcome of s. aureus coagulase/mannitol

Answer 39

positive

Question 40

what are some tests used to identify aureus over epidermidis?

Answer 40

blood agar plate, coagulate or mannitol

Question 41

what is s. aureus on a blood agar plate?

Answer 41

beta hemolytic

Question 42

what is epidermidis on a blood agar plate?

Answer 42

gamma or alpha

Question 43

what does a mannitol salt plate do?

Answer 43

contains phenol red ph indicator that turns yellow if mannitol is fermented

Question 44

what does streptococci produce?

Answer 44

hemolysins

Question 45

what do hemolysins do

Answer 45

act on red blood cells

Question 46

what test would you use to measure differences in the organisms ability to ferment different sugars, the presence of various enzymes and physical characteristics such as motility?

Answer 46

biochemical tests

Question 47

what is a macconkey agar plate?

Answer 47

selective/differential medium

Question 48

what color is lactose fermenting organisms on macconkey agar

Answer 48

bright pink

Question 49

what color is non lactose fermenting on macconkey agar?

Answer 49

cream

Question 50

what is a XLD plate?

Answer 50

selective/differential medium

Question 51

on an XLD plate, what color are lactose, sucrose and xylose fermentation?

Answer 51

yellow

Question 52

what color are non fermenting colonies on an XLD

Answer 52

red

Question 53

what is indole

Answer 53

product from cleaving amino acid tryptophan

Question 54

what is the ELISA test used for?

Answer 54

identification of plant, animal, and human viruses

Question 55

what are the two primary causes of water pollution?

Answer 55

dumping of sewage | fecal pollution of animals and humans

Question 56

what are the two microbiological methods commonly used to determine if a given water sample is polluted?

Answer 56

total number of microorganisms present in the water | indicator organisms

Question 57

what indicator organisms are most commonly used

Answer 57

coliform

Question 58

what are the two most important methods applied to detect coliform organisms

Answer 58

multiple tube fermentation | membrane filter technique

Question 59

what are the three tests of multiple tube fermentation

Answer 59

presumptive confirmed completed

Question 60

what is the most probable number test and why is it useful?

Answer 60

counting bacteria that reluctantly form colonies but grow readily in liquid mediu

Question 61

what is the confirmed test?

Answer 61

confirms presence of coliforms

Question 62

what are advantages of the membrane filter technique over the multiple tube fermentation

Answer 62

better reproducibility of results greater sensitivity shorter time