1
Q
What type of microorganism is Bdellovibrio spp. (B. bacteriovorus)?
A
Gram-negative predator
2
Q
Bdellovibrio spp. can be used to control which human intestinal pathogens?
A
Salmonella spp., Shigella spp., and E. coli
3
Q
What biological control method is suggested for poultry farms using Bdellovibrio?
A
Spraying poultry farms with Bdellovibrio to reduce potential contamination
4
Q
Where and when did another biological control method have its start?
A
Early 1900s at the Pasteur Institute in France
5
Q
Who isolated bacteriophages from patients recovering from bacillary dysentery?
A
Felix d’Herelle
6
Q
After numerous in vitro tests, what did d’Herelle conclude about bacteriophages?
A
That bacteriophages participated in the destruction of the bacteria causing dysentery
7
Q
What event slowed down bacteriophage therapy development?
A
The introduction of penicillin, which ushered in the age of antibiotics
8
Q
What do phages produce that attack bacterial cell walls?
A
Lytic enzymes (lysins)
9
Q
What is the function of lysins?
A
→ They attack bacterial cell walls, facilitating release from their specific bacterial host
10
Q
What current research effort is being pursued regarding phages and lysins?
A
Evaluating them as bacterial control methods
11
Q
What microbial products (toxins) can be used to control susceptible microbial populations?
A
Microbial toxins such as bacteriocins
12
Q
By what mechanisms does heat kill microorganisms?
A
Denaturing enzymes and proteins,
degrading nucleic acids, and
disrupting cell membranes
(Denature, degrade, disrupt)
13
Q
What is the Thermal Death Point (TDP)?
A
Lowest temperature at which all microbes in a liquid suspension will be killed in 10 minutes
14
Q
What is the Thermal Death Time (TDT)?
A
Minimal length of time in which all bacteria will be killed at a given temperature
15
Q
What is Decimal Reduction Time (DRT) or D value?
A
Time (in minutes) required to kill 90% of microorganisms or spores in a sample at a given temperature
16
Q
In what industry is DRT commonly used?
A
Canning industry
17
Q
How does moist heat kill microorganisms?
A
coagulating their proteins
18
Q
In general, which is more effective:
moist heat or dry heat?
A
Moist heat
19
Q
What temperature and condition is used in boiling as a microbial control method?
A
100°C or more at sea level
20
Q
What microbial forms are killed by boiling within 10 minutes or less?
A
Vegetative forms of bacterial pathogens,
almost all viruses,
fungi, and their spores
21
Q
Which microbial forms are not destroyed quickly by boiling?
A
Endospores and some viruses
22
Q
How long can the Hepatitis virus survive boiling?
A
Up to 30 minutes
23
Q
How long can endospores survive boiling?
A
20 hours or more
24
Q
Give an example of a bacterial toxin that is heat resistant.
A
Staphylococcal enterotoxin
25
What does reliable sterilization with moist heat require?
Temperatures above that of boiling water
26
What is an autoclave?
A **chamber filled with hot steam** under pressure
27
What is the **preferred method of sterilization**, *unless material is damaged by heat, moisture, or high pressure?*
Autoclave
28
What **temperature does steam in an autoclave** reach at **twice atmospheric pressure?**
121°C
29
When is autoclaving most effective?
When **organisms contact steam directly** or are contained in a small volume of liquid
30
Within **how many minutes** are all organisms and endospores **killed in an autoclave?**
15 minutes
31
Why might autoclaving **require more time for certain materials?**
**More time is needed** to reach the **center of solid objects or large volumes of liquid**
32
What kind of chamber does an autoclave represent? Or what does it look like
A closed chamber with high temperature and pressure
33
Who developed pasteurization and for what purpose?
Louis Pasteur,
to prevent the spoilage of beverages
34
What is the main use of pasteurization?
**reduce microbes responsible for spoilage** of beer, milk, wine, juices, etc.
35
What is the classic (historical or batch) method of pasteurization?
Milk is exposed to **63–65°C** for **30 minutes**
36
What is the **High Temperature Short Time Pasteurization** (HTST), also called **flash pasteurization**, used today?
Milk is exposed to **72°C for 15 seconds**
37
What is Ultra High Temperature Pasteurization (UHT)?
Milk is treated at **134°C for 1 second** and then **cooled very quickly in a vacuum chamber**
38
What is **Ultra High Temperature Sterilization?**
Milk is treated at **140°C** (284°F) for **1–3 seconds**
39
A method of disinfecting liquids
Pasteurization
40
Heats them to a certain temperature but does not totally destroy pathogens
pasteurization
41
What is an advantage of pasteurization (especially UHT milk)?
Milk can be stored at room temperature for several months
42
List the standard pasteurization conditions for:
Classic batch method → 63°C for 30 minutes
HTST (flash) → 72°C for 15 seconds
UHT sterilization → 140°C for 1 second
UHT pasteurizarion → 134°C for 1 second
43
What is the **main effect of pasteurization** on microorganisms?
reduces spoilage organisms and pathogens
44
A process of intermittent sterilization
Tyndallization
45
Who developed tyndallization, and what was his profession?
John Tyndall, a British physicist
46
What was tyndallization used for originally?
destroy heat-resistant microorganisms in dust
47
What does the process of tyndallization use?
Steam (**30–60 minutes**) to destroy vegetative bacteria
48
How many times is steam exposure repeated in tyndallization?
Three times
49
**How long are the incubations** between steam exposures in tyndallization?
23 to 24 hours
50
Why are incubations included in tyndallization?
They **permit remaining spores to germinate into heat-sensitive vegetative cells,** which are **then destroyed** during subsequent steam exposures
51
How does dry heat kill microorganisms?
oxidation effects
52
What are the **three main dry heat sterilization methods?**
Direct flaming, incineration, hot air sterilization
53
What is direct flaming used for?
Sterilizing inoculating loops and needles
54
What indicates sterilization during direct flaming? (The indication that it is heated)
Heating the metal until it **has a red glow**
55
What is incineration used for?
Sterilizing **disposable items** (e.g., paper cups, dressings) and **biological waste**
56
How is **hot air sterilization** carried out?
Objects are placed in an **oven for 2 hours at 170°C**
57
Why does **dry heat sterilization require longer time** than moist heat?
Because **dry heat transfers heat less effectively** to a cool body than moist heat
58
Name one type of oven used for dry heat sterilization of laboratory materials.
Class 100 sterilization oven
59
What is a Class 100 sterilization oven used for?
**Depyrogenation** of glass, Teflon, and other heat-resistant materials
60
What is the principle of filtration in microbial control?
**Removal of microbes by passage of a liquid or gas** through a **screen-like material with small pores**
61
What types of materials are sterilized by filtration because they are heat sensitive?
Vaccines, enzymes, antibiotics, and some culture media
62
What does HEPA stand for, and where are HEPA filters used?
**High Efficiency Particulate Air Filters**;
used in operating rooms and burn units to **remove bacteria from air**
63
What are membrane filters characterized by in flitration?
Uniform pore size
64
In what fields are membrane filters commonly used?
Industry and research
65
What is the **pore size range of membrane filters** used to filter most bacteria?
0.22 µm and 0.45 µm
66
Which microorganisms are not retained by 0.22–0.45 µm pores? In flitration
Spirochetes, mycoplasmas, and viruses
67
What pore size retains all viruses and some large proteins?
0.01 µm
68
What method is used to sterilize heat-sensitive liquids such as culture media, antibiotics, vaccines, and enzymes?
Filtration
69
In filtration, how is sterility achieved?
**Solution is passed through a membrane with pores so small** that bacteria cannot pass through;
the resultant solution is sterile
70
What laboratory equipment is associated with membrane filter sterilization?
**Laminar flow biological safety cabinet**
71
What **type of filter** do biological safety cabinets employ, and what are they made of?
High-efficiency particulate air (HEPA) filters,
a type of depth filter made from **fiberglass**
72
What percentage of particles 0.3 µm or larger do HEPA filters remove?
99.97%
73
What mechanisms do HEPA filters use to remove particles?
Physical retention and electrostatic interactions
74
Can HEPA filters be made to adsorb viruses?
Yes
75
What is the smallest virus size?
0.1 µm and smaller
76
What is the function of laminar flow biological safety cabinets or hoods
**Force air through HEPA filters** and **project a vertical curtain** of sterile air across the cabinet opening
77
In what application are laminar flow hoods commonly used?
Cell culture
78
What is the largest bacteria size?
0.45 um
79
What is the smallest virus size?
0.01 µm
80
What temperature range defines refrigeration, and what effect does it have?
**0–7°C**; bacteriostatic effect
81
How does refrigeration inhibit microbial growth?
**Reduces the metabolic rate** of most microbes so they cannot reproduce or produce toxins
82
What temperature defines freezing in microbial control?
Below 0°C
83
What is **flash freezing**, and does it kill microbes?
Rapid freezing method; does not kill most microbes
84
What is **slow freezing**, and why is it more harmful to microbes?
Freezing that occurs gradually; **ice crystals disrupt cell structure**
85
What fraction of vegetative bacteria may survive freezing for 1 year?
Over one third of vegetative bacteria
86
How long does it take freezing to kill most parasites?
few days
87
Is freezing bacteriostatic or bactericidal?
**Bacteriostatic** (slows bacterial growth but does not kill all bacteria)
88
What happens during freeze-thaw cycles
Some bacteria may be killed, but many survive
89
Does freezing result in sterility?
No
90
Why can microbes not grow or reproduce during desiccation?
Because of the absence of water
91
Can microbes remain viable during desiccation?
Yes, some may remain viable for years
92
How long can Neisseria gonorrhoeae survive desiccation?
About one hour
93
How long can Mycobacterium tuberculosis survive desiccation?
Several months
94
How resistant are viruses to desiccation?
Fairly resistant
95
Which bacterial genera may survive desiccation for decades?
Clostridium spp. and Bacillus spp.
96
What is the overall microbial control effect of desiccation?
Bacteriostatic (not sterilizing)
97
How are bacterial cultures often preserved in labs?
In a freeze-dried state
98
using high concentrations of salts and sugars to create a hypertonic environment
Osmotic Pressure
99
What happens to cells in a hypertonic environment (plasmolysis)?
Water leaves the cell, plasma membrane shrinks away from the cell wall
100
Does plasmolysis always kill the cell?
No, the cell may not die but usually stops growing
101
Which organisms are more resistant to high osmotic pressures?
Yeasts and molds
102
Which bacteria on human skin are fairly resistant to high osmotic pressure?
Staphylococcus spp.
103
How does osmotic pressure preserve food?
High salt or sugar content prevents bacterial growth
104
What **types of food resist bacterial growth** due to osmotic pressure?
Honey, jelly, salted meats
105
What is the overall microbial control effect of osmotic pressure?
Bacteriostatic
106
Which organisms can still grow under osmotic pressure?
Molds and yeasts
107
What are the three main types of radiation used to kill microbes?
Ionizing radiation, non-ionizing radiation, and microwave radiation
108
Give examples of ionizing radiation
Gamma rays, X rays, electron beams, higher energy rays
109
What wavelength is characteristic of ionizing radiation?
Short wavelengths, less than 1 nanometer
110
What is the mechanism of action of ionizing radiation?
Dislodges electrons from atoms and forms ions
111
What are the effects of ionizing radiation on DNA?
Causes mutations in DNA and produces peroxides
112
What industries use ionizing radiation for sterilization?
Medical supplies, pharmaceuticals, disposable items, food industry
113
What is a major disadvantage of ionizing radiation?
Penetrates human tissues and may cause genetic mutations in humans
114
What reactive molecule does ionizing radiation form by ionizing water?
Reactive OH radicals
115
What do OH radicals disrupt?
DNA and other organic molecules
116
What are some items sterilized by ionizing radiation?
Plastics, medical supplies, gloves, syringes, heat-sensitive items
117
What type of radiation is non-ionizing?
Ultraviolet (UV) light
118
What is the wavelength of **non-ionizing radiation** compared to ionizing?
Longer than 1 nanometer
119
What energy level does non-ionizing radiation have?
Low to moderate energy
120
How does UV radiation damage DNA?
producing thymine dimers, which cause mutations
121
What are some applications of UV radiation?
**Disinfecting** operating rooms, nurseries, cafeterias;
**sterilization of surfaces** and heat-sensitive items
122
What are the disadvantages of UV radiation?
Damages skin and eyes, does not penetrate paper, glass, cloth, dirt films, or water effectively
123
What laboratory tool emits UV radiation for sterilization?
Germicidal lamps
124
What is the biggest limitation of UV radiation?
Very low penetrating power
125
What is the wavelength range of microwave radiation?
1 millimeter to 1 meter
126
Is microwave radiation ionizing or non-ionizing?
Non-ionizing
127
Heat is absorbed by water molecules, generating heat that kills microbes by denaturing proteins and disrupting cellular structures
Microwave Radiation
128
What microorganisms can microwaves kill through heat?
Bacteria, viruses, and fungi
129
What are three applications of microwave radiation?
Food industry, sterilization of medical equipment, and waste treatment
130
How is microwave radiation used in the food industry?
Cooking and reheating, incidentally reducing microbial populations and ensuring food safety
131
How is microwave radiation used in medical sterilization?
Sterilizing certain instruments that cannot withstand traditional methods like autoclaving
132
How is microwave radiation used in waste treatment?
Treating medical waste to reduce microbial contamination before disposal
Microbiology
flashcards
Decks in class (22)
# Cards
-
Module 6106
-
Module 7181
-
Module 8. 1132
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Module 8.2115
-
Module 8.3283
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Module 9188
-
9191
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11.1191
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11.2170
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Module 11.2160
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Module 12 (Slide 1 To 39)94
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Module 12 (Slide 40 To 65)76
-
Module 12 (66-101)156
-
Module 12 (-110 Last)25
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LAB EXAM 1 EXERCISES31
-
LAB EXAM 1 PPT CULTURE MEDIA107
-
Module 13 (VIRUSES)64
-
Module Virology Pt.1 (RNA VIRUSES)85
-
Module Virology Part 2 (DNA)57
-
Module VIROLOGY Part 3 (Introduction)98
-
RNA (Picorna-Coronaviridae)83
-
RNA VIRUS (REO - RHABDOVIRIDAE)49
