Lab Practical Flashcards
(159 cards)
1
Q
Presence or absence of oxygen can be very _________ to the growth of bacteria
A
Important
2
Q
Sodium thioglycate broth
A
Type of reducing media that is used to reduce the amount of oxygen concentration within the test tube
3
Q
_____ is added to reduce the diffusion of oxygen to the rest of the media
A
Agar
4
Q
Dye added to indicate where oxygen is present in the medium
A
resazurin
5
Q
Turns pink in the presence of excess oxygen
A
Resazurin
6
Q
Obligate Aerobe
A
1.Require oxygen. 2.See growth at the top of broth only
7
Q
Obligate anaerobe
A
- Can’t tolerate oxygen
- Lack catalase
3.See growth at bottom of broth only
8
Q
Majority of bacteria
A
Facultative anaerobes
9
Q
Capable of living with or without oxygen
A
Facultative anaerobe
10
Q
Growth is seen throughout medium but more at the surface
A
Facultative anaerobe
11
Q
Cannot use oxygen but tolerate it well
A
Aerotolerant anaerobe
12
Q
Most bacteria use fermentative metabolism
A
Aerotolerant anaerobe
13
Q
Growth is seen throughout the medium, but more at the bottom
A
Aerotolerant anaerobe
14
Q
Microaerophiles
A
Grow best in an atmosphere with increased carbon dioxide (5-10%)and lower concentrations of oxygen.
15
Q
To culture microaerophiles on petri dishes, a ______ jar is needed
A
CO2
16
Q
Generally, ____ kills microbes and _____ inhibits microbial growth
A
Heat
cold
17
Q
How is heat sensitivity determined?
A
Heat sensitivity is genetically determined and partially reflected in the optimal growth ranges
18
Q
Bacteria exhibit different tolerances to the application of_____
A
Heat
19
Q
Examples of dry heating
A
1.Hot air ovens
2.incineration
20
Q
Moist heat examples
A
- Pasteurization
2.boiling - autoclave
21
Q
________ transfers heat energy to the microbial cell more efficiently
A
Moisture
22
Q
Pasteurization maintains temperature at ____ for ______ mins
A
145 F for 30 mins
23
Q
Pasteurization maintains temperature at _____ for __ ________ to kill microbes that are pathogenic or cause spoilage
A
160 F for 15 seconds
24
Q
Boiling
A
212 F for 10 minutes kills vegetative bacterial cells but does not inactivate endospores
25
Most effective method of moist heat sterilization
Autoclave
26
What is autoclaving?
Use of steam under pressure
27
More pressure ________ the boiling point of water and produces steam with a higher temperature
Raises
28
What are the conditions for autoclaving?
15 PSI at 250F for 15 minutes
29
Sufficient to kill endospores and render materials sterile
Autoclaving
30
Thermal death time
The effectiveness of heat against a specific microbe
31
TDT
Length of time required to kill all bacteria in a liquid culture at a given temperature
32
TDP thermal death point
Temperature required to kill all bacteria in a liquid culture in 10 minutes (less common)
33
DRT decimal reduction time
Time in minutes in which 90% of a population of bacteria at a given temperature will be killed.
34
Antimicrobial agents
Control the growth of microbes
35
Disinfectants
Chemical agents used on inanimate objects to lower the level of microbes on their surface
36
Antiseptics
Chemicals used on living tissue to decrease number of microbes
37
Bactericidal agents
Those that result in bacterial death
38
-cidal
Lethal
39
Bacteriostatic agents
Those that cause temporary inhibition of growth
40
-static
Inhibiting
41
DRT Decimal reduction time
for the most common and persistent microbes identified at a healthcare facility should be determined
42
Limited to bacteriocidal compounds cannot be used for bacterostatic
Dilution test
43
The effectiveness of a disinfectant can be determined by the amount of resulting growth
Use-dilution test
44
Common and persistent microbes identified at healthcare facilities
1.Salmonella enterica
2.Staphylococcus aureus
3. Pseudomonas aeruginosa
45
Use dilution test
Rings are dipped into standardized cultures, removed, and dried.
46
Rings are placed into a solution of disinfectant at the concentration recommended for 10 minutes at 68° F
Use-dilution test
47
Effectiveness of disinfectant can be determined by the amount of resulting growth
Use dilution test
48
Antibiotics
Substance produced by a microorganism that inhibits the growth of other microorganisms
49
Antimicrobial or chemotherapeutic drugs
Antimicrobial chemicals used internally whether natural (antibiotic) or synthetic
50
Disk diffusion method
1.Petri dish is innoculated with desired microbe
2. Various antimicrobial agents are placed on the surface of the agar
3. Antimicrobial agent diffuses
51
Zone of inhibition
No growth around the disk
1. Helps us see the diffusion rate of antimicrobial agent
2. Growth rate of microbe
52
Kirby-Bauer test
Standardized disc diffusion method to minimize variance
Uses Mueller-Hinton agar
53
The bigger the zone of inhibition the more ______ the antibiotic is
Effective
54
Which bacteria produce 70% of all antibiotics
Streptomycetes
55
Earliest writers classified bacteria solely on their
Morphological characteristics
56
Biologic characters
Refers to information about the metabolism of bacteria
57
Exoenzymes
Break down large molecules outside a cell. Smaller molecules released by this reaction are taken into the cell and further degraded by endoenzymes
58
Endoenzymes
Degrade the products of exoenzymes
59
Majority of enzymes function on the inside of the cell
Endoenzymes
60
Enzymes that are released from the cell to catalyze reactions outside the cell
Exoenzymes
61
Mainly hydrolytic enzymes
Exoenzymes
62
What do exoenzymes do?
1.Leave the cell
2.break down large substrates
3.need the addition of water
4. transport smaller components into the cell
63
Example of exoenzyme
Amylase hydrolyzes the polysaccharide starch to glucose
64
Starch hydrolysis begins
Clear
65
Add iodine to see presence in substrate outside
Colony
66
O/F test
1.Oxidative vs fermentative
2. OF medium is semisolid nutrient agar deep
67
Low concentration of peptone is
Growth medium
68
Desired carbohydrate can be added
O/F test
69
Oxidative catabolism requires the presence of
O2
70
Fermentative catabolism does not require oxygen but may occur in its presence
Some gas may occur
71
Peptone are
Food
72
Bromothymol blue turns green to yellow in the presence of
Acids
73
Bromothymol blue turns green to yellow in the presence of acids
Catabolism of carbohydrates
74
Both tubes turn yellow
Carbohydrate catabolism= fermentation
75
Yellow at top half
Acids produced as intermediates in respiration
76
Yellow in open tube only
Aerobic conditions only
77
Dark blue
1.Alkaline conditions
2.peptone used but no carbohydrate
3.ammonia production
78
More specific
Fermentation
79
Carbohydrate fermentation
Many bacteria produce organic acids and carbon dioxide gases from carbohydrate fermentation
-glucose
80
MRVP broth
Used to distinguish organisms that produce large amounts of acid from glucose and organisms that produce neutral product Acetoin
81
Citrate agar
Used to test for ammonia production
82
Phenol red turns from red to yellow when
Acid is present
83
Carbohydrate fermentation test
1.Peptone is used for microbe growth
2. Each tube has the same microbe but different carbohydrates
84
Durham tube
Small inverted tube used to observe gas released by the microbe
85
This is not a test you want to leave longer than 24 hours because the color will change back to red
Carbohydrate fermentation test
86
Why can't you leave the carbohydrate fermentation test for more than 24 hours
The color will change back to red because peptone is used after the carbohydrate is gone
87
MR test
Test for acid to neutral pH changes based on products produced by microbes
88
Red
pH is below 4.4
89
Orange red
pH is 4.4-6.0
90
Yellow
pH is above 6.0
91
MR VP
Methyl red voges proskauer
92
Is a glucose supplemented nutrient broth
MR VP
93
Voges proskauer test
Test for production of acetoin detection by the addition of reagent 1 (alpha napthol) and reagent 2 (KOH)
94
VP
Upper part is red
Acetoin present= positive test
95
VP Upper part is brown
No acetoin=negative test
96
Simmons citrate agar
Green=control and negative
Prussian blue=positive
97
Some bacteria ferment citrate which can be useful for identifying bacteria
Contain citrate lyase
98
When citric acid is in solution, it loses a proton to form
Citrate ion
Sole carbon source
99
Citrate lyase break down citrate to form
pyruvate which can be reduced in fermentation
100
Bacteria use ammonium for sources of nitrogen and produce
Ammonia
101
Bromothymol blue changes to blue when the medium is
Alkalized
102
Small chain of amino acids
Peptide
103
Large chain of amino acids
Polypeptide
104
Amino acids are used primarily in
Anabolic reactions
105
Bacteria can hydrolyze the peptides or Polypeptides to release amino acids
Use amino acids as energy sources when carbohydrates are unavailable
106
When is the nutrient gelatin test positive?
If it stays liquid because it signifies the breakdown of proteins
107
Exoenzymes gelatinase hydrolyzes gelatin
It liquefies but does not solidify when cooled
108
Litmus milk
Bacteria can hydrolyzes the protein in milk called casein
109
Skim milk
Litmus indicator (blue/purple)
110
Cason hydrolysis peptonization
Turns clear blue
111
Lactose fermentation
Turns pink with acid
112
Excessive acid coagulation
Curd
113
Catabolism of litmus milk test
Alkaline reaction is purple
114
Reduce litmus
Turns white in lower part of two
115
Reduce litmus
Turns white in lower part of tube
116
Urea
Urea is a waste product of protein digestion in most vertebrates and is excreted in urine
117
Urease
Breaks down urea releasing ammonia
118
Urea agar contains
peptone, glucose, urea, and phenol red
119
Phenol red in urease test is originally
Orange
120
In urease test, yellow means a pH of
6.8
121
Urease test: Bright pink means a pH of
8.4
122
Once the amino acids are taken into a bacterial cell, various metabolic processes can occur using endoenzymes
1. Use as carbon and energy source
2. Have to remove the amino group
123
Removing the amino group is called
Deamination makes H2S and Indole
124
During deamination
Amino acid to ammonia, then released from the cell
125
Urease breaks down urea releasing
Ammonia
126
Deamination produces
Indole and H2S
127
Some bacteria have de-sulfhydrase enzymes
Remove hydrogen sulfide from the sulfur containing amino acids cysteine and methionine
128
De-sulfhydrase enzymes gas
Make rotten egg gas
129
H2S can also be produced from the reduction of inorganic compounds such as
thiosulfate
130
SIM Medium
Sulfide indole motility
131
Why do we use an inoculation needle in the sim medium?
To see if the bacteria grows out from where it was stabbed
132
Motility
The growth of black hydrogen sulfide is going to spread instead of being in a line
133
What is added to the Sim medium? What kind of salt?
Heavy metal salt such as iron, thiosulfate
134
Positive results shows a blackened area
Sulfide
135
Positive result shows red at top
Indole
136
Positive result shows black all over test tube
Motility
137
What does the hydrogen sulfide production test do?
Tests sulfide, indole and motility
138
Indole test
Useful diagnostic tool. Some bacteria deaminate amino acid tryptophan and produce indole, indigo
139
Uses MIO deep
Indole test
140
Which reagent is used for the indole test?
Kovac's reagent
141
MIO stands for
Motility
Indole
Ornithine decarboxylase
142
Respiration
Living organisms obtain energy by removing electrons or oxidizing substrates
143
Example of respiration
Glycolysis; glucose is oxidized to pyruvic acid; The electron transport chain carries electrons; O2 is the final electron acceptor in aerobic respiration.
144
Cytochromes in the plasma membrane of bacterial cells carry electrons to
O2
145
Oxidase test
Used to determine the presence of cytochrome C
Four classes of cytochromes have been identified
146
Catalase test
During respiration, hydrogen combines with oxygen forming hydrogen peroxide.
Hydrogen peroxide is lethal to the cell
147
During respiration hydrogen combines with oxygen forming
Hydrogen peroxide
148
Nitrate reduction rest
Used to determine the ability to reduce nitrates
149
During anaerobic respiration, some bacteria reduce
1.Nitrate to nitrite
2.Nitrite to nitrous oxide
3.Nitrous oxide to nitrogen gas
150
Uses to reagents to detect nitrites
Reagent a & reagent b
151
Dimethyl-alpha-naphthylamine
Reagent A
152
Sulfanilic acid
Reagent B
153
What indicates a positive nitrate reduction test?
Red color-> nitrite is present= positive
154
Why should you check for gas first in the nitrate reduction test
Nitrogen has been reduced to nitrous, oxide (N2O) or nitrogen gas (N2)
155
A second test is used to further check if a negative is found
Zinc dust
Red color-> zinc will reduce nitrates to nitrites
156
Salt tolerance test
Tests the ability of an organisms ability to survive in high salt concentration
157
Percentage of salt for salt tolerance test
6.5% to 7.5%
158
What is a positive result of the salt tolerance test?
Cloudy is a positive result. Clear is a negative result
159
Which organisms are expected to grow in high salt concentrations?
Staphylococci enterococci, Aerococci
