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Microbio > Lab exam 2 > Flashcards

Lab exam 2 Flashcards

1
Q

biology of coliforms

A
  • members of the family Enterobacteriaceae
  • ex: Enterobacter, Klebsiella, Citrobacter, Escherichia
  • Gram negative
  • Lactose fementing (w acid and gas production)
  • found in environement, gut, and feces
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2
Q

what are non-coliform eneterics?

A

members of the family Enterobacteriaceae that
1) do NOT ferment lactose
2) are part of enteric flora or true pathogens

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3
Q

what are coliforms used for?

A

bacterial indicator of the sanitary quality of food and water
because:
1) they may be associated with the sources of pathogens contaminating water
2) this analysis of drinking water is simple, cheap, and efficient

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4
Q

Multiple Tube Fermentation Method

A

standardized test to estimate the total number of coliforms in a sample
1) innoculate many broth tubes with Durham tubes
2) tubes observed for bacterial growth and gas production
3) # of tubes positive are cross referenced to determine MPN

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5
Q

what is MPN

A

most probably number of coliforms per 100 mL of sample

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6
Q

Soil

A

a storehouse for 3 microorganisms
1) typical bacteria
2) actinomycetes (decomposers and humus producers)
3) fungi (decomposer saprophytes)

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7
Q

what media is used for Soil Microbial Count lab?

A

Glycerol Yeast Extract Agar (GYEA)- for actinomycetes. Not enough nutritive value for typical bacteria or fungi
TrypticSoy Agar (TSA)-for broad range of bacteria but not fungi
Sabouraud Dextrose Agar (SDA)- for fungi but will also support bacteria. Ampicillin/ Streptomycin added to discourage bacterial growth

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8
Q

Antimicrobials

A

ALL microbial agents used to treat bacterial infections
1) antibiotics
2) bactericidal
3) bacteriostatic

(both natural and synthetic agents)

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9
Q

antibiotics

A

natural antimicrobial agents produced by microorganisms
ex: penicillin

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10
Q

Bactericidal vs. Bacteriostatic

A

bactericidal: kills microbe
bacteriostatic: stops growth but doesn’t kill microbe

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11
Q

Kirby-Bauer test

aka disk diffusion test

A

tool for measuring the effectiveness of antimicrobials against pathogens
1) plate inoculated to form “lawn” of bacteria
2) disk coated with antimicrobials are placed on a plate
3) plates incubated to allow growth of bacteria and time for agent to diffuse
If organism is susceptive, a clear zone will appear around disk

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12
Q

what does a clear zone in Kirby-Bauer test mean?

A
  • growth is inhibited
  • size of zone depends on sensitivity of the bacteria to the specific agent
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13
Q

what are species classified by?

A

their cardinal temperatures (min, max, and optimum)

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14
Q

thermophiles

A

adapted to temp above 45

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15
Q

obligate thermophiles

A

will not grow at temp below 40

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16
Q

facultative thermophiles

A

will grow below 40

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17
Q

extreme thermophiles

A

grow best above 80

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18
Q

Culturing in vitro

A
  • acids from carb fermentation and alkaline products from protein metabolism are enough to destroy enzyme integrity
  • buffers are added to growh media to maintain equilibrium
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19
Q

obligate (strict) aerobes

A
  • organisms that require oxygen for respiration
  • will grow at the top of media where oxygen is most plentiful
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20
Q

facultative anaerobes

A
  • grow in the presence or absence of oxygen
  • When an oxygen gradient exists, will grow through the gradient but will appear denser at the top
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21
Q

obligate (strict) anaerobes

A
  • even small amounts of oxygen are lethal
  • will only grow in the lower regions of the medium
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22
Q

aerotolerants

A
  • don’t require oxygen and are not adversely affected by it
  • will grow uniformly throughout the medium
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23
Q

microaerophiles

A

survive only in environments with lower than atmospheric oxygen levels

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24
Q

what is Thioglycollate used for?

A
  • differential medium used to determine the oxygen requirements of microorganisms by observing its growth patterns in the media
  • oxygen removed during autoclaving will diffuse back into medium as tubes cool to room temp
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25
Q

Eosin Methylene Blue Agar

A

selective and differential medium
* inhibits growth of Gram (+) organisms
* based on fermentation
* non-lactose fermenters = colorless colonies
* lactose fermenteres = colored colonies

metallic green colonies = E. Coli
brown center = enterobacter aerogenes

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26
Q

Hektoen Enteric Agar

A

Selective and differential medium
* inhibits growth of Gram (+)
* enterics that ferment carbs turn yellow or salmon colored
* hydrogen sulfide reduction produces black precipitate
To isolate Salmonella and Shigella from other enterics
* salmonella = black colonies
* shigella = green colonies

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27
Q

Operons

A
  • closely linked genes that help to regulate protein synthesis
  • each includes a promoter and structural genes that encode for enzymes
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28
Q

bacterial transformation

A

bacterial cells pick up DNA from the environment and make use of the genes it carries

29
Q

what operon and promoter was used for the bacterial transformation lab?

A

operon- arabinose

promoter- Pbad (araB, araA, araD)
that code for enzymes used to digest arabinose

30
Q

what happens if arabinose is present?

A

1) binds to araC
2) changes its shape
3) enables RNA pol to attach and transcribe the genes that come after the promoter
4) organism can then produce enzymes that digest the arabinose

allows transcription of gene of interest

31
Q

what does the pGLO plasmid have?

A
  • GFP gene
  • antibiotic resistance genes (resistance to ampicillin to differentiate between cells that were successfully transformed from those that were not)

(doesn’t fluoresce under UV light)

32
Q

epidemiology

A

study of causes, occurrence, transmission, distribution, and prevention of diseases in a population

33
Q

what are the 2 types of transmission of infectious disease?

A

1) common source epidemics
2) propagated transmission

34
Q

common source epidemics

A
  • when a disease affects many people at one
  • ex: contaminated water that infects many people at once
35
Q

propagated transmission

A

when a disease is transmitted from person to person

36
Q

incidence rate

A

number of new cases of a disease reported in a defined population during a specific period of time

= number of new cases/ size of at-risk population

37
Q

prevalence rate

A

number of cases of a disease at a specific point in time in a defined population

= number of existing cases / size of-at risk population

38
Q

hemagglutination

A

clumping of RBC indicating a positive reaction

39
Q

what determines blood type?

A

antigen on RBC

(agglutination with that anti- antiserum)

40
Q

Rh factor

A
  • complex system of antigens
  • D antigen proved most potent genetically and therefore most important in hemolytic disease and transfusions
41
Q

D antigens are inherited ____ from ABO blood type

A

independently

42
Q

Hemolytic Disease of the Newborn

A
  • Rh (-) mom has baby with Rh (+) father
  • if mom has been sensitized to Rh(+) blood, immune system will make antibodies to attack her baby’s RBC
43
Q

difference of sufficient anti-A/B and anti-D antibodies in the patient

A

anti-A/anti-B: agglutination hemolysis of donor blood cells
anti-D: cause extravascular hemolysis

44
Q

bioremediation

A

process of using living things to clean up environmental pollution

45
Q

bacteriophages/ phages

A

viruses that infect bacteria

46
Q

lytic cycle

A
  • main method of viral replication
  • uses host cell’s machinery to produce large amounts of viral components
  • after components assembled, host cell lyses, releasing newly formed viruses
47
Q

lysogenic pathway

A
  • phage DNA integrates into the host cell chromosome without harming host
  • phage DNA in this state is called PROPHAGE
  • prophage remains dormant and is duplicated with every subsequent cell division of the host
  • prophage is activated in response to stress and is excised from DNA of host cell
  • phage enters lytic cycle
48
Q

plaques

A

clearings from lysis of cells growing in a lawn on agar plate

used to calculate phage concentration

49
Q

phage titer

A

phage density

titer= PFU /(vol. plated x dilution)

50
Q

what affects virus’ ability to infect host?

A

virus’ ability to attach to a specific host receptor (this can further differentiate species down to strains (ex: E. coli HB101, E. coli B)

51
Q

UV-A
UV-B
UV-C

A

A: longest wavelength (315-400 nm)
B: wavelenthths 280-315 nm
C: wavelengths 100-280 nm (most detrimental to bacteria- irreparable DNA damage and death of organism)

52
Q

UV light

A
  • type of electromagnetic energy
  • shorter, higher energy wavelength than visible light
53
Q

wavelength

A

distance between adjacent wave crests

54
Q

how can prolonged exposure to UV radiation be lethal to cells?

A

DNA absorbs UV radiation, and the energy is used to form pyrimidine dimers (covalent bonds between adjacent pyrimidines)

55
Q

how do bacteria repair DNA damage?

A

1) E. coli can perform light repair (photoreactivatio)
2) using DNA photolyase or excision repair (dark repair)

56
Q

mutation

A

a stable, heritable change in the nucleotide sequence of DNA

57
Q

spontaneous vs induced mutation

A

spontaneous- arise occasionally in all bacteria and develop in the absence of any agent
induced: result of a bacterium’s exposure to a mutagen (physical or chemical)

58
Q

why are spontaenous mutations due antibiotic resistance easy to detect?

A

because they grow in the presence of antibiotic concentrations that owuld typicaly inhibit growth of normal bactera

59
Q

formite transmission

A
  • inanimate objects that can carry and spread disease and infectious agents
  • aka passive vectors
60
Q

what are NOT reasons to streak for individual colonies?

A
  • decrease cell density
  • observe colony morphology
61
Q

what consitutes a pure culture?

A

contains a single bacterial species

62
Q

what is the purpose of heat fixing?

A
  • to adhere bacterial cells to the slide
  • to kill the bacterial cells
63
Q

What is the benefit of using a differential stain versus a simple or negative stain?

A

differential: differentiate between organisms or between parts of the same organism

64
Q

why may a Gram stain not yield clear results?

A
  • poor technique while perfomring Gram stain
  • age of culture
  • emulsion is too thick
65
Q

what is the purpose of the mordant when gram staining

A

to enhance violentstaining by forming a crystal violet-iodine complex

66
Q

Would you expect Gram-positive or Gram negative bacteria to be more susceptible to antibiotics?

A

Gram-positive because they lack outer lipid membrane

67
Q

most commonly caused DNA mutation by UV radiation

A

thymine-thymine dimers

68
Q

Which of the following reasons would best explain why you need to remove the lid from your bacterial plate when exposing the bacteria to UV radiation in order to cause mutation?

A

UV radiation has a short wave length and has trouble going through plastic and glass

69
Q
A

Microbio (5 decks)

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