Lecture 4 - Microbial Growth Requirements Flashcards
1
Q
___ is the increase in the number of cells or microbial population rather than in the size of individual cells.
A
Microbial Growth
2
Q
To increase the population of microorganisms, their ____ and ____ requirements must be provided.
A
nutritional; physical
3
Q
What are the factors affecting microbial growth? (3)
A
- Biochemical Factors (Nutrition)
- Generation Time
- Physical Factors
4
Q
What are the biochemical factors (nutrition) affecting microbial growth? (3)
A
- Macronutrients
- Micronutrients
- Vitamins
5
Q
____ supplies cells with chemical tools (nutrients) that they need to make monomers of the macromolecules that mainly comprise microbial cells.
A
Microbial Nutrition
6
Q
____ are made up of chemical elements; they are extracellular substances that provide a microbial cell with materials to (1) build protoplasm and (2) generate energy.
A
Nutrients
7
Q
____ are nutrients required in relatively larger amounts.
A
Macronutrients
8
Q
____ are nutrients required in lesser quantities.
A
Micronutrients
9
Q
A ____ is any nutrient material prepared/used for the growth and cultivation of microorganisms in the laboratory.
A
Culture Medium
10
Q
What is Culture Media for? (3)
A
- for the growth and maintenance of microbial cultures
- to favor the production of particular compounds
- to study microbial action on some constituents of the medium
11
Q
What are the types of culture media (based on physical state or consistency)? (3)
A
- Liquid
- Semi-solid
- Solid
12
Q
___ is a type of culture media that consists of the ff:
composition: w/ NO solidifying agent
purpose/s: Inoculum Preparation; Fermentation Test
examples: Nutrient broth; Lactose broth
A
Liquid Culture Medium
13
Q
___ is a type of culture media that consists of the ff:
composition: w/ 0.1-0.5% solidifying agent
purpose/s: Motility Test
examples: Sulfur Indole Motility (SIM) Medium
A
Semi-Solid Culture Medium
14
Q
___ is a type of culture media that consists of the ff:
composition: w/ 1.5-2.0% solidifying agent
purpose/s: Colony Morphology Observation; Hemolysis and Pigmentation Characterization
examples: Nutrient Agar; Blood Agar
A
Solid Culture Medium
15
Q
____ is a complex polysaccharide (derived from red algae). It is used as a solidifying agent for culture media in Petri plates, slants, and deeps. It has no nutritive value and is generally not metabolized by microbes. It is not affected by the growth of bacteria.
A
Agar
16
Q
Agar liquifies at ____.
Agar solidifies at ____.
A
100°C
~40°C
17
Q
What are the types of culture media (based on chemical composition)? (2)
A
- Synthetic or Chemically-Defined Culture Media
- Complex Culture Media
18
Q
____ is a type of culture media that consists of the ff:
- all components are chemically-defined (precise nutrient composition and amounts.
- examples: Glucose, Inorganic Salt Phosphate
A
Synthetic or Chemically-Defined Culture Medium
19
Q
____ is a type of culture media that consists of the ff:
- not all components are chemically-defined.
- examples: Nutrient Agar, Yeast Extract
A
Complex Culture Medium
20
Q
____ is a type of culture media prepared from pure chemicals and the exact chemical composition (kinds and amounts) is known.
A
Synthetic or Chemically-Defined Culture Medium
21
Q
What are some disadvantages of using synthetic (chemically-defined) culture medium? (3)
A
- preparation is time-consuming
- microorganisms grow relatively slow
- prepared only for microorganisms with known nutritional requirements
22
Q
____ is a chemically undefined medium and its precise chemical composition (kinds) is unknown. It contains certain similar ingredients but its chemical composition varies slightly from batch to batch. It is made from extracts from natural materials (beef, blood, casein, yeast, soybeans).
A
Complex Culture Medium
23
Q
What are some advantages of using complex culture medium? (2)
A
- easy to prepare
- support rapid growth of most microorganisms
24
Q
What are the types of culture media (based on principal purpose, function, or application? (5)
A
- General Purpose
- Differential
- Selective
- Enrichment
- Assay
25
What type of culture media consists of the ff:
characteristics: can support most or almost all types of species
examples: Nutrient Agar, Tryptic Soy Agar, Brain Heart Infusion Agar
General Purpose
26
What type of culture media consists of the ff:
characteristics: can distinguish visually one type of bacteria from another
examples: Eosin
Differential
27
What type of culture media consists of the ff:
characteristics: allows the growth of a specific type of microorganism only
examples: Methylene Blue, Mannitol Salt Agar (MSA)
Selective
28
What type of culture media consists of the ff:
characteristics: used to increase the number of microorganisms with unusual physiological
characteristics; contains special nutrients for microorganisms of interest
examples: Cellulose Agar, Petroleum Broth, Blood Agar
Enrichment
29
What type of culture media consists of the ff:
characteristics: used for assay of vitamins, amino acids, antibiotics; may be used for qualitative or quantitative production of a compound by a microorganism
examples: Fermentation Media, TSI Agar, Vitamin B12 Assay Medium
Assay
30
___ is a type of culture media that allows the growth of a specific type of microorganism only and suppresses the growth of others. It contains selective agents/additives/toxic chemicals (salts, dyes, antibiotics, and other inhibitors). It requires an extreme pH value or an unusual carbon source to favor the growth of a particular organism.
Selective Medium
31
What are some examples of selective media? (3)
1. Thayer-Martin Agar (Neisseria gonorrhoeae)
2. NA with Penicillin (Gram-negative bacteria)
3. Thiosulfate Citrate Bile Salts Sucrose (TCBS) Agar
32
____ is a type of culture media that can distinguish or differentiate visually one type of bacterium from another. It identifies microorganisms by the appearance of their colonies and exploits the ability of a particular microorganism to change the appearance of the medium.
Differential Medium
33
What are some examples of differential media? (2)
1. Blood Agar (Streptococcus species)
2. Mac-Conkey Agar (E. coli and lactose fermenters)
34
____ contains general nutrients and 5% sheep blood. It is useful for cultivating fastidious organisms and for determining the hemolytic capabilities of an organism.
Blood Agar
35
____ are exoenzymes produced by some bacteria that lyse red blood cells and degrade hemoglobin.
Hemolysins
36
Beta-hemolysin breaks down the red blood cells and hemoglobin completely. This leaves a clear zone around bacterial growth. Such results are referred to as ____.
β-hemolysis (beta hemolysis)
37
_____ partially breaks down the red blood cells and leaves a greenish color behind.
α-hemolysis (alpha hemolysis)
38
The greenish color left behind by α-hemolysis (alpha
hemolysis is caused by the presence of _____, a by-product of the breakdown of hemoglobin.
Biliverdin
39
____ refers to if the organism does not produce hemolysins and does not break down the blood cells, no clearing will occur.
γ-hemolysis (gamma hemolysis)
40
____ is a type of culture media that is used to increase the number of microorganisms with unusual physiological characteristics (pathogens from a mixed culture). It contains special nutrients for the microbe of interest and inhibitory substances to suppress unwanted microorganisms.
Enrichment Medium
41
____ is a type of media that is used for the assay of vitamins, amino acids, and antibiotics. It is used for qualitative or quantitative production of such a compound by a microorganism. It is of prescribed composition.
Assay Medium
42
____ is a type of culture media that contains an indicator that changes its color when a bacterium grows in them. Some of its examples are Blood Agar and Mac Conkey.
Indicator Medium
43
___ is a type of culture media that contains any fermentable substances (glucose, arabinose, lactose, starch). It consists of 1% of the sugar in peptone water. It contains a small tube (Durham tube) for the detection of gas by the bacteria.
Sugar Medium
44
____ is a differential medium that contains 1% lactose, 1% sucrose, and 0.1% glucose (dextrose), ferrous sulfate, and the pH indicator phenol red. This test is normally performed on Gram-negative bacteria. It is also used to differentiate enterics based on the ability to reduce sulfur and ferment carbohydrates.
Triple Sugar Iron (TSI) Agar
45
____ is a type of culture media that is used for transporting samples (prevents microbial proliferation; maintains the viability of microorganisms). Some of its examples are Stuart's medium (non-nutrient soft agar gel containing a reducing agent); buffered glycerol saline (for enteric bacilli).
Transport Medium
46
___ is a type of culture media that used to provide additional information for the identification of the bacterium. Some examples of this culture media are Triple Sugar Iron (TSI) Agar (Sugar Fermentation), SIM Medium (Indole Test), Citrate Utilization, and Christensens Urease Medium (Urease Test).
Biochemical Reaction Medium
47
___ is a test used to detect indole production by an organism. A positive test is indicated by a pink ring. A negative test is indicated by a yellow ring.
Indole Test
48
_____ is done in Simmon's Citrate medium. It is used to detect the ability of certain bacteria to utilize citrate as the sole source of carbon. It contains sodium citrate and bromothymol blue as the indicator.
Citrate Utilization Test
49
What are the two types of culture media if based on oxygen requirement? (2)
1. Aerobic Media
2. Anaerobic Media
50
____ is a type of culture media used to grow anaerobic organisms. Some examples of this are Robertson's cooked meat medium and Thioglycolate medium.
Anaerobic Medium
51
____ is a type of culture media that is used to grow aerobes or aerobic microorganisms.
Aerobic Medium
52
What are the physical factors affecting microbial growth? (7)
1. pH
2. Temperature
3. Oxygen Concentration
4. Moisture
5. Hydrostatic Pressure
6. Osmotic Pressure
7. Radiation
53
____ is an expression of hydrogen ion concentration in water.
pH
54
pH values less than 7 – ____
pH values greater than 7 - ____
acidic
basic
55
The optimum pH for most bacteria is near neutrality or ____.
pH 7
56
What is the pH range of each classification of organisms based on pH?
1. Acidophiles < pH 5.4
2. Neutrophiles pH 5.4 - 8.5
3. Alkaliphiles pH 7.5 - 11.5
57
____ are acid-loving organisms. They can be found in acidic lakes and/or in the gastrointestinal tract. These include most fungi since they are acid-tolerant and their optimum temperature is 5 or below. Also include some algae, bacteria, and several archaea. A high H+ concentration is required for these organisms to maintain cell membrane stability.
Acidophiles
58
____ include most human disease-causing bacteria (human blood and tissues pH = 7.2 - 7.4) and protozoans and most bacteria (pH 6.5 - 7.5).
Neutrophiles
59
____ are base-loving organisms that live in soda lakes and/or high-carbonate soils. Such organisms are Bacillus, Vibrio cholerae (pH 9), Alcaligenes
faecalis (>pH 9), and Agrobacterium (pH 12). Some also produce hydrolytic enzymes (proteases and lipases).
Alkaliphiles
60
____ is one of the most, if not the most, important environmental factors affecting the growth and survival of microorganisms.
Temperature
61
What are the three critical temperatures (affecting enzyme function) or the three cardinal temperatures? (3)
1. Minimum Growth Temperature
2. Optimum Growth Temperature
3. Maximum Growth Temperature
62
____ is the lowest temperature at which cells can divide. The membranes solidify and will slow the transport process.
Minimum Growth Temperature
63
____ is the temperature at which cells divide most rapidly. The enzymatic reaction occurs at the maximal possible rate.
Optimum Growth Temperature
64
____ is the highest temperature at which cells can divide. It causes protein denaturation, the collapse of the cell membrane, and cell lysis.
Maximum Growth Temperature
65
What are the classes of microorganisms if based on the temperature? (4)
1. Psychrophiles
2. Mesophiles3
3. Thermophiles
4. Hyperthermophiles
66
What are the respective temperature range and optimum temperature for each temperature class of microorganisms?
1. Psychrophiles (TR: <0 to 20°C) (OT: 15°C)
2. Mesophiles (TR: 10 to 48°C) (OT: 37°C)
3. Thermophiles (TR: 40 to 72°C) (OT: 60°C)
4. Hyperthermophiles (TR: 65 to 110°C) (OT: 80°C)
67
____ are cold-loving organisms and they grow best at -10 to -20°C. They live mostly in cold water and soil (Arctic and Antarctic regions) and can cause spoilage of refrigerated food).
Psychrophiles
68
____ is a bacteria that can be present in raw milk, foods made from raw milk, and a variety of processed meats. Unlike other germs, it can grow even in the cold temperature of the refrigerator. It can be killed by cooking and pasteurization.
Listeria monocytogenes
69
____ include most bacteria including pathogens. It is the most common group of microorganisms. It is best in 25 to 40°C and found in warm-blooded animals. Some of its examples are thermoduric microorganisms (Bacillus, Micrococcus, Lactococci, Corynebacterium). These can withstand short periods of exposure to high temperatures; can cause food spoilage.
Mesophiles
70
____ are heat-loving organisms and are best in 40 to 72°C. They can be found in compost heaps and hot springs. They can be identified as contaminants in dairy products.
Thermophiles
71
What are the two categories of thermophiles? (2)
1. Obligate Thermophiles - temperatures above 37°C
2. Facultative Thermophiles - temperatures both above and below 37°C
72
____ are extreme heat-loving organisms and are best in 65 to 110°C. They can be found in boiling hot springs, geysers, and hot water vents.
Hyperthermophiles
73
____ are unsaturated (polyunsaturated) fatty acids in phospholipids; with enzymes functional at low temperatures; active transport occurs well at low temperatures.
Psychrophiles
74
_____ are saturated fatty acids in phospholipids; heat-stable proteins and enzymes.
Thermophiles
75
____ have no fatty acids in their membrane (phytane); has a lipid monolayer.
Hyperthermophiles
76
What is the purpose of a lipid monolayer? (1)
It stabilizes the membrane at high temperatures.
77
____ are bacteria that require oxygen to grow.
Aerobes
78
____ are bacteria that do not require oxygen to grow.
Anaerobes
79
What are the 5 classes of microorganisms (based on oxygen)? (5)
1. Obligate Aerobes
2. Obligate Anaerobes
3. Microaerophiles
4. Facultative Anaerobes
5. Aerotolerant Anaerobes
80
____ are microorganisms that must have free oxygen for aerobic respiration (e.g Pseudomonas spp.)
Obligate Aerobes
81
____ are microorganisms that do not require/use oxygen for metabolism. These organisms can be found in muds, sediments of lakes, rivers, oceans, marshes, water-logged soils, canned foods, intestinal tracts, sewage treatment systems, anoxic environments.
Obligate Anaerobes
82
____ are microorganisms that grow best in the presence of small amounts of free oxygen (e.g Campylobacter, a capnophile - organism that requires high CO2 conc.).
Microaerophiles
83
____ are microorganisms that ordinarily carry aerobic metabolism when oxygen is present but shift to anaerobic metabolism when oxygen is absent (e.g Staphylococcus, E. coli).
Facultative Anaerobes
84
____ are microorganisms that can survive in the presence of oxygen but do not use it in their metabolism (e.g Lactobacillus).
Aerotolerant Anaerobes
85
Why is O2 necessary for aerobic cellular respiration?
Oxygen oxidizes substrates to produce energy.
86
What are some anaerobic culture methods? (5)
1. using reducing media containing chemicals (e.g Thioglycolate) that combine with O2
2. using anaerobic jars (GasPak)
3. Novel Method in Clinical Labs: adding oxyrase to growth media (OxyPlate)
4. working in a glove box
5. using candle jars
87
____ is an essential ingredient of bacterial protoplasm. It is needed by actively metabolizing cells.
Water
88
The effect of drying varies: (3)
1. Treponema pallidum - highly sensitive
2. Staphylococcus sp. - can stand for months
3. Endospore-former Bacteria and Xerophiles - resistant to dessication (removal or loss of moisture)
89
____ is the minimum pressure needed to be applied to a solution to prevent the flow of water across a semi-permeable membrane.
Osmotic Pressure
90
Most bacteria require an ____ environment or a _____ environment for optimum growth.
Isotonic; Hypotonic
91
A hyperosmotic environment leads to ____.
Plasmolysis (loss of water)
92
Too high osmotic pressure outside the cell leads to:
water loss --> inhibits growth or kill bacterial cells
93
The application of osmotic pressure is by using salt or sugar as preservatives. What are some examples of this? (4)
1. salting of fish
2. sugaring of fruits
3. brining of vegetables
4. jams, marmalades, preserves, and pickles
94
___ are organisms that can grow at relatively high salt concentration (up to 10%).
Osmotolerants
95
____ are salt-loving organisms. They require relatively high salt conc. for growth (e.g archaea require NaCl conc. of 20% or higher). They require moderate to large quantities of salt. Their membrane transport system actively transports sodium ions out of the cell and concentrates potassium ions. They are typically found in the ocean (optimum: 3.5% salt concentration) and also are found in exceptionally salty bodies of water (Dead Sea, Brine Vats).
Halophiles
96
What are the three classes of halophiles + their NaCl conc.? (3)
1. Low Halophiles 1-6% NaCl
2. Mild or Moderate Halophiles 6-15% NaCl
3. Extreme Halophiles 15-30% NaCl
97
____ is pressure exerted by standing water, in proportions to its depth. It doubles every 10 meter increase in depth (e.g 50-m deep lake - 32x atmospheric pressure).
Hydrostatic Pressure
98
____ are bacteria that live at high pressures. Their membranes and enzymes (3-D configuration) require high pressure to function properly.
Piezophiles (Barophiles)
99
____ exhibit optimal reproduction rates at hydrostatic pressures exceeding 10MPa, found throughout the deep-biosphere.
Piezophiles
100
In ____, all known bacterial piezophiles fall into this category. They exhibit optimal reproduction rates at hydrostatic pressures exceeding 10MPa and at temperatures ranging from 2-4°C, found throughout the deep-biosphere.
Psychropiezophiles
101
With ____, the only current example is the archaeon Pyrococcus yayanosii. They exhibit optimal reproduction rates at 52MPa and 98°C.
Thermopiezophiles
102
With ____, visible light is the source of energy for photosynthesis (photosynthetic microorganisms: Cyanobacteria, Volvox).
Radiation/Radiant Energy
103
What is the difference between Direct Damage and Indirect Damage by ionizing radiation?
1. Direct Damage -
2. Indirect Damage -
104
How do most bacteria reproduce?
Binary Fission
105
What happens in binary fission? (5)
1. replication of chromosomes
2. cells double in size
3. septum formation
4. completion of septum with formation of distinct walls
5. cell separation
106
___ refers to the interval for the formation of two cells from one cell. It is the time required for a bacterium to give rise to 2 daughter cells under optimum conditions.
Generation Time
107
Generation Time of the ff:
1. Escherichia coli - ___
2. Staphylococcus aureus - ___
3. Mycobacterium tuberculosis - ___
4. Treponema pallidum - ___
1. Escherichia coli - 20 mins
2. Staphylococcus aureus - 27-30 mins
3. Mycobacterium tuberculosis - 792-932 mins
4. Treponema pallidum - 1980 mins
108
How to calculate generation times?
N = No2^n
g = t/n
109
What does the ff stand for:
1. N
2. No
3. n
4. g
5. t
1. N = final cell number
2. No = initial cell number
3. n = no. of generations that have occurred during the period of exponential growth
4. g = generation time
5. t = hours or minutes of exponential growth
110
What are the four phases of bacterial growth curve? (4)
1. Lag
2. Log or Exponential
3. Stationary
4. Decline or Death Phase
111
T or F
The four phases of bacterial growth curve only apply to individual cells, not to populations of cells.
F
They only apply to populations of cells.
112
In the ____ phase, there is NO significant or immediate increase in cell numbers but there may be an increase in the size of the cell. It is also called the ADAPTATION phase.
The is metabolically ACTIVE (synthesize enzymes
and new components; utilizes various molecules
from the medium; produce large quantities of
energy).
This is the period when microorganisms are introduced into fresh culture medium.
Lag
113
In the ____ or ____ phase, cells start dividing and their number increases exponentially.
Here, organisms divide at their most rapid rate.
The population of organisms DOUBLES in each generation time.
The cells are in their HEALTHIEST state.
It is influenced by environmental conditions and genetic characteristics of organisms.
Here, bacteria are MORE SUSCEPTIBLE to antibiotics.
Population is also most uniform in terms of chemical, metabolic, and physiologic properties.
Log (Logarithmic); Exponential
114
In the ____ phase, cell division decreases due of nutrients and accumulation of toxic products; inadequate oxygen supply; pH change.
Here, growth rate TAPERS OFF.
Equilibrium EXISTS between dying cells and the newly formed cells (new cells produced at the same rate as old cells die).
Cell functions continue.
This is usually where the production of secondary metabolites (small, bioactive molecules) occur.
Stationary
115
In the ____ phase, the population decreases due to the DEATH of cells.
Here, conditions in the medium become less and LESS SUPPORTIVE of cell division.
The number of live cells DECREASES at a logarithmic rate (but slower).
Cells undergo LYSIS or INVOLUTION (assume a variety of unusual shapes).
There are also more spores than vegetative cells that survive.
Decline (Death)
116
Enumerate the four morphological and physiological alterations during growth. (4)
1. Lag Phase - maximum cell size towards the end of lag phase.
2. Log Phase - smaller cells, stain uniformly.
3. Stationary Phase - irregular staining, sporulation and production of exotoxins.
4. Phase of Decline - involution forms (with aging).
117
What are the physical methods in controlling microbial growth? (4)
1. Heat Treatment
2. Irradiation
3. Filtration
4. Mechanical Removal
118
Give one example of a chemical method in controlling microbial growth. (1)
1. Antimicrobial Chemicals
119
____ refers to killing or complete elimination of all viable microorganisms. This uses agents - sterilants or sterilizing agents (e.g ethylene oxide, steam under pressure.
Sterilization
120
____ refers to the elimination or reduction of pathogens from inanimate objects or surfaces. It uses agents - disinfectants (e.g alcohol, formaldehyde, chlorine).
Disinfection
121
____ refers to the reduction of microbial populations to levels considered safe by public health standards (e.g iodine, chlorine)
Sanitization
122
____ refers to the prevention of infection in living tissues using chemicals (e.g iodine, alcohol, hydrogen peroxide).
1. Antisepsis
123
___ is considered to be one of the most useful methods of microbial control. It is reliable, safe, relatively fast, and inexpensive. It is used to sterilize or decrease microbial numbers. It can be in the form of moist heat or dry heat.
Heat
124
____ refers to the temperature that kills all bacteria in a 24-hour old broth culture at neutral pH in 10 minutes.
Thermal Death Point
125
____ refers to the time required to kill all bacteria in a particular culture at a specified temperature.
Thermal Death Time
126
___ is a form of heat that consists of efficient penetrating properties. It destroys microorganisms by irreversibly coagulating their proteins. It can be through boiling, pasteurization, or pressurized steam.
Moist Heat
127
___ requires to be at 100°C. At this temperature, most bacteria are destroyed and some viruses are inactivated. This also kills vegetative cells and eukaryotic spores within 10 minutes.
Boiling
128
____ refers to the use of brief heat treatment (moderately high temperature) to reduce the number of spoilage organisms and kill pathogens (e.g Salmonella, Mycobacterium).
This process is also used to make wine, beer, vinegar, milk, juices.
It significantly reduces the number of heat-sensitive microorganisms; does not significantly alter the quality of food.
It increases the shelf-life of food and protects consumers.
Pasteurization
129
What are the four methods under pasteurization? (4)
1. Low-Temperature Holding (LTH) - 62.8°C for 30 minutes
2. High-Temperature-Short-Time (HTST) Method - milk: 72°C, 15 seconds (flash method); ice cream: 82°C, 20 seconds
3. Ultra-High-Temperature (UHT) Method - 140-150°C (several seconds); involves complex cooling processes; e.g boxed juices, coffee creamers.
4. Mechanical Pasteurization (non-food) - e.g hospital anesthesia mask: 80°C, 15 minutes.
130
____ include using pressure cookers and autoclaves. This can be achieved by heating water in an enclosed vessel that achieves temperatures above 100°C. It can also be in 15 minutes, 15 psi, at 121°C (kills endospores and disrupts viruses' nucleic acids).
Only items that can be penetrated by steam and withstand heat and moisture can undergo this treatment (e.g surgical instruments, microbiological media, reusable glassware, microbial cultures, and biohazards before disposal).
This also ensures Clostridium botulinum endospores are destroyed.
Pressurized Steam
131
____ refers to fractional steam sterilization or intermittent sterilization. This is for materials that can be destroyed at more than 100°C. This puts organisms exposed to 90-100°C for 30 minutes for 3 consecutive days.
This is used for some canned foods and laboratory media.
Tyndallization (Nonpressurized Steam)
132
___ is not as efficient as wet heat (lower penetrating properties). It requires longer times and higher temperatures. It is only used for metal objects and glassware. It can be achieved by using an oven or an open flame (incineration).
Dry Heat
133
____ uses dry heat; oxidizes cell components to ashes.
Incineration
134
___ uses dry heat; oxidizes cell components and irreversibly denatures proteins. It is used to sanitize Petri dishes and glass pipettes. It is by default at 170-180°C for 1 hour. It can be used on powders, oils, or anhydrous materials.
Dry Heat Oven/Hot Air
135
What are some low-temperature methods? (2)
1. Refrigeration - 4-5°C; limited to a few days because bacteria and molds continue to grow still at low temperatures.
2. Freezing or Deep Freezing - 0-95°C; used to preserve food in homes and food industries; slows the rate of chemical reactions in bacterial cells.
136
What are the two types of filtration methods? (2)
1. Fluid Filtration - remove organisms from heat-sensitive fluids.
2. Air Filtration - high-efficiency particulate air (HEPA): remove from air nearly all microorganisms with diameter greater than 0.3 µm.
137
What are the two types of filtration methods? (2)
1. Fluid Filtration - remove organisms from heat-sensitive fluids.
2. Air Filtration - high-efficiency particulate air (HEPA): remove from air nearly all microorganisms with diameter greater than 0.3 µm.
138
___ is used to preserve food (in the absence of water that inhibits the action of enzymes). It is also used to minimize the spread of infectious agents (e.g Treponema).
Drying/Desiccation
139
____ is also referred to as lyophilization. It is the drying of material from a frozen state. It is for long-term preservation (e.g instant coffee, culture preservation).
Freeze-Drying
140
___ causes plasmolysis of bacterial cells. It is said that high salt or sugar conc. creates a hyperosmotic medium, drawing water out of microorganisms.
Increased Osmotic Pressure
141
____ include radio waves, microwaves, visible and UV light rays, X rays, and gamma rays.
Radiation
142
Radiation can be categorized into two: (2)
1. Ionizing - has enough energy to free electrons from the atoms or molecules they are attached to, and therefore ionizing them.
2. Non-ionizing - lacks the energy to break these same molecular bonds and cannot free electrons from atoms or molecules.
143
____ are less reliable than heat; suitable for treating large surfaces and heat-sensitive items; some are non-toxic; can be used as preservatives (bacteriostatic).
Chemical Agents
144
What are some examples of chemical agent? (8)
1. Alcohols
2. Aldehydes
3. Phenols or Phenolics
4. Halogens
5. Heavy Metals
6. Sterilizing Gases
7. Surface Active Agents or Surfactants
145
____ coagulate enzymes and other essentials and damages lipid membranes. They are used as antiseptics for degerming or as disinfectants for treating instruments and surfaces (e.g 60-80% ethyl or isopropyl alcohol.
Alcohols
145
____ coagulate enzymes and other essentials and damages lipid membranes. It is used as antiseptics for degerming or as disinfectant for treating instruments and surfaces (e.g 60-80% ethyl or isopropyl alcohol.
Alcohols
146
___ inactivate proteins and nucleic acids (e.g glutaraldehyde, formaldehyde (formalin (aqueous 37% formaldehyde): kill most forms
of microorganisms), orthopthaldehyde (OPA).
Aldehydes
147
___ disrupts the cell membrane, denatures proteins, and inactivates enzymes. (e.g phenol, cresol, xylenon, triclosan).
Phenols/Phenolics
148
____ oxidizes cell constituents (e.h iodine, chlorine).
Halogens
149
___ denatures enzymes and essential proteins (e.g silver nitrate (prevents ophthalmic gonorrhoeae); copper sulfate (algicide); silver sulfadiazine (used on burns); merthiolate (disinfects skin mucous membranes).
Heavy Metals
150
____ denatures protein; for heat-sensitive items (catheters, plastic Petri plates); e.g ethylene oxide, ozone, chlorine dioxide.
Sterilizing Gases
151
____ include soaps and acid-anionic detergents; mechanical removal of microorganisms. Also included are cationic detergents, they disrupt the cell membrane and denature proteins.
Surface Active Agents or Surfactants
152
____ inhibit microbial metabolism (e.g sorbic acid, benzoic acid, calcium propoionate) and are widely used in foods/cosmetics).
Organic Acids
153
What is another oxidizing agent that can be used to control microbial growth? (1)
1. Hydrogen Peroxide (oxidation of cell components)
