Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIOL 240 > Module 6B > Flashcards

Module 6B Flashcards

Cultivating Microorganisms

1
Q

what are 3 methods to quantify microbes

A
  • direct counts
  • viable cell counts
  • turbidity measurements
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

which quantifying method allow you to differentiate between viable cells and dead cells

A

viable cell counts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the steps to using a Petroff-Hauser counting chamber

A
  1. add a drop or two of bacterial suspension to the center of the chamber
  2. lower a cover slip over the grid, suspension spreads out evenly and excess flows into the side channels
  3. use a microscope to count the cells in the grid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

how can you count the number of viable cells with direct counts

A

use a viability stain (e.g. acridine orange; binds to nucleic acids within the cells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what do viable cell counts count

A

colony-forming units (CFUs)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how is it ensured that the number of colonies is countable

A

serial dilutions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how are pure culture obtained for viable cell counts

A

spread plate or pour plate method

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how are CFUs/mL calculated

A

multiplying the number of colonies by the inverse of the dilution factor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how is turbidity measured

A

using a spectrophotometer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what do the turbidity values mean

A

light absorbance is proportional to the abundance of cells within a growth medium: more light absorbance => more cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the phases of growth curves

A
  • lag phase
  • exponential phase
  • stationary phase
  • death phase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what adjustments are needed in the lag phase of growth curves

A

can include producing new proteins for transporting and metabolizing newly available carbon and nutrients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

define: generation time

A

time it takes a species of bacteria (or archaea) to divide in the exponential phase [same as the population doubling time]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

define: growth rate

A

inverse of generation time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

define: growth yield

A

maximum population density, or the amount of biomass that can be recovered in early stationary phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what phase does a continuous culture maintain

A

exponential growth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

how is a continuous culture made

A

fresh media is continuously provided to the culture at a limited rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

define: chemostat

A

system that brings in fresh medium and removes old medium/microbes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what are the types of filters

A
  • pre-filter
  • polymer membrane filter
  • nucleopore membrane filter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

how are viruses filtered

A

with ultrafiltration methods (pore size: 10-100nm)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what are examples of pre-filters

A
  • depth filter
  • cheesecloth
  • Whatman filter paper
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

which filter removes the largest particles

A

pre-filters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what are polymer membrane filters made of

A

cellulose acetate or cellulose nitrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what are polymer membrane filters used for

A

routine sterilization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what are nucleopore membrane filters made of

A

polycarbonate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

how thick are the pores of nucleopore membrane filters

A

10 um

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

how are nucleopore membrane filters made

A

formed by exposing polycarbonate films to radiation, tiny cracks are enlarged by a chemical etching process

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what are nucleopore membrane filters useful for

A

microscopy

29
Q

describe the consistency of pore size of polymer membrane filters and nucleopore membrane filters

A

polymer membrane filter - pores somewhat variable in diameter
nucleopore membrane filter - consistent pore size

30
Q

how does heat kill microorganisms

A

by denaturing proteins and nucleic acids

31
Q

what types of microorganisms are harder to destroy with heat

A

hypothermophiles and endospores

32
Q

what do autoclaves use to sterilize

A

pressure and heat

33
Q

why do autoclaves use pressure

A

it prevents fluids from evaporating or boiling

34
Q

what standard values are used in autoclaves

A

pressure: 15 psi
temperature: 121 C
time: 20 mins

35
Q

what is the use of pasteurization

A
  • to decrease microbial “load” - the total number of microorganisms in a food product
  • destroys all pathogens
36
Q

what are 3 commonly used processes with pasteurization

A
  • high temperatures for short times (HTST) [72 C for 15 sec]
  • ultra-high temperature (UHT) [135 C for < 1 sec]
  • extended shelf life [ESL] - filtering the material and then using a low-temp pasteurization
37
Q

why is refrigeration/freezing effective for preservation

A

it reduces microbial growth and spoilage, the formation of ice crystals can be harmful to the membranes and cell walls of microorganisms

38
Q

how are cultures rapidly frozen

A
  • for cultures that we want to preserve, add a cryoprotectant like dimethylsulfoxide (DMSO) or glycerol
  • lower the culture directly into liquid nitrogen
39
Q

what is the advantage of flash freezing

A

it preserves viability

40
Q

what is electromagnetic radiation used for

A

eliminates microorganisms from surfaces or any materials that allow light to penetrate

41
Q

why is UV light damaging to DNA

A

it forms thymine dimers in DNA (two T bases become covalently linked)

42
Q

what surfaces are electromagnetic radiation good for

A

non-living surfaces, NOT used for tissues

43
Q

what advantage does ionizing radiation have over electromagnetic radiation

A

it penetrates materials well

44
Q

what protein & DNA damage does ionizing radiation induce

A
  • double-stranded DNA breaks
  • stray electrons
  • hydroxide ions
  • hydride radicals
45
Q

what are some examples where ionizing radiation is used

A
  • eliminating insects from materials and supplies
  • exposing tissue or cartilage used for grafting in medical procedures
46
Q

what are nonselective antimicrobial agents

A

they are toxic to any cells, any protein is targeted (target specific groups on proteins and amino acids)

47
Q

what are selective antimicrobial agents

A

they target specific microbial groups

48
Q

what does Penicillin act on

A

Gram-positive cell walls

49
Q

what are the three ways that antimicrobial agents kill cells

A
  • bacteriostatic
  • bacteriocidal
  • bacteriolytic
50
Q

what is the purpose of bacteriostatic antimicrobial agents

A

they inhibit growth (don’t kill), buy time for the immune response to clear the infection

51
Q

what is the difference between bacteriocidal and bacteriolytic

A

bacteriocidal:
- result in cell death
- viability decreases
- cells are still visible

bacteriolytic:
- result in cell lysis
- number of visible cells decrease

52
Q

what is the difference between disinfectants and antiseptics

A

disinfectants: used on inanimate surfaces
antiseptics: used on living tissue

53
Q

how do alcohols disinfect

A

they dissolve the membranes of bacteria

54
Q

where are alcohols used for disinfection

A
  • used in laboratory settings
  • present in most hand sanitizers
55
Q

how do phenolic compounds disinfect

A

affect the membrane of bacteria

56
Q

where are phenolic compounds used for disinfection

A

added to products like soaps, deodorants, and cosmetics

57
Q

how do oxidizing agents disinfect

A

they remove electrons indiscriminately from proteins and DNA

58
Q

where are oxidizing agents used for disinfection

A

commonly added to swimming pools and hot tubs

59
Q

how do quaternary ammonium compounds disinfect (Benzalkonium chloride)

A

affect the bacterial membranes

60
Q

how does glutaraldehyde disinfect

A

it crosslinks proteins, used as a preservation agent

61
Q

how is glutaraldehyde used for disinfection

A

often used to prepare biological specimens

62
Q

what are antibiotics

A

antimicrobial agents that are produced by microorganisms

63
Q

how do antibiotics work

A

they bind to proteins or organelles and interrupt the energy management of the cell

64
Q

what is an example of a broad-spectrum antibiotic

A

tetracycline

65
Q

what are 2 examples of narrow-spectrum antibiotics

A
  • polymixin B
  • penicillin
66
Q

how is an antibiotic sensitivity assay prepared

A
  1. microorganisms is spread over the surface of a plate
  2. paper disks are impregnated with different antibiotics are placed on the surface of the plate
  3. the plate is incubated overnight
  4. the amount of clearing provides an indication of how sensitive your microorganism is to an antibiotic
67
Q

what is the decimal reduction time (D value)

A

time required to kill 90% of the target organisms under specific conditions

68
Q

what is the decimal reduction dose (D10)

A

radiation dose required to kill 90% of the target organisms under specific conditions

BIOL 240 (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions