C5 - Microbial Growth and Nutrition Flashcards
1
Q
What are the two main categories of requirements for microbial growth?
A
Physical and Chemical
2
Q
What physical factors are required for microbial growth?
A
Temperature, pH, and osmotic pressure
3
Q
What chemical factors are necessary for microbial growth?
A
Sources of carbon, nitrogen, sulfur, phosphorus, oxygen, trace elements, and organic growth factors
4
Q
Primary groups on the basis of their preferred range of temperature:
A
a. Psychrophiles/Cryophiles
b. Psychrotrophs
c. Mesophiles
d. Thermophiles
e. Hyperthermophilic
f. Extremophiles
5
Q
What are cold-loving microbes that grow well between 0°C and 20°C called?
A
Psychrophiles/Cryophiles
6
Q
What is an example of a psychrophile?
A
Listeria monocytogenes
Yersinia enterolitica
7
Q
What temperature range do psychrotrophs prefer?
A
Optimum between 20°C and 30°C but can grow well at lower temperatures
8
Q
What are moderate-temperature-loving microbes that grow well between 20°C and 40°C, with an optimal range of 30°C to 37°C, called?
A
Mesophiles
9
Q
temperature optimum between 20°C and 30°C but grow well at lower temperatures
important cause of food spoilage
A
Psychrotrophs
10
Q
What is an example of a mesophile commonly encountered in clinical laboratories?
A
pathogenic bacteria
11
Q
What are heat-loving microbes that grow best at temperatures between 50°C and 60°C called?
A
Thermophiles
12
Q
Name an example of a thermophile.
A
Bacillus stearothermophilus
13
Q
What term describes microbes that can survive temperatures above the boiling point of water?
A
Hyperthermophilic
14
Q
What are prokaryotes that are able to survive in extreme conditions such as high temperatures and the absence of oxygen called?
A
Extremophiles
15
Q
What temperature range do psychrophiles/Cryophiles grow well in?
A
0°C to a maximum of 20°C
16
Q
What is the temperature range that psychrotrophs grow optimally in?
A
20°C to 30°C
17
Q
At what temperature range do mesophiles grow?
A
20°C to 40°C
18
Q
What is the optimal temperature range for mesophiles?
A
30°C to 37°C
19
Q
What temperature range do thermophiles prefer?
A
50°C to 60°C
20
Q
What temperature range can hyperthermophilic microbes survive in?
A
Above the temperature of boiling water
21
Q
What temperature range do psychrophiles/Cryophiles thrive in?
A
0°C to 20°C
22
Q
What is the lowest temperature at which a species will grow called?
A
Minimum Growth Temperature
23
Q
What is the temperature at which a species grows best called?
A
Optimum Growth Temperature
24
Q
What is the highest temperature at which growth is possible for a species called?
A
Maximum Growth Temperature
25
What is the term for the lowest or minimum time required to kill an organism under a constant temperature?
Thermal Death Time
26
What is the lowest temperature required to kill a microorganism in a constant time called?
Thermal Death Point
27
What type of organisms are most commonly found in the temperature range of 30°C (35-37°C)?
Mesophilic organisms
28
At what temperature do diagnostic laboratories usually incubate cultures for bacterial growth?
35°C
29
Which two bacteria can grow at both 35°C and 42°C?
Pseudomonas aeruginosa and Campylobacter
30
What is the pH range where most bacteria grow best?
pH 6.5 to 7.5
31
What pH range do Neutralophiles grow best in?
pH 6.0–8.0
32
What is the internal pH maintained by Neutralophiles over an external range of 5.5–8.5?
About 7.5
33
What is the optimum pH range for Acidophiles?
As low as pH 3.0
34
What is the internal pH maintained by Acidophiles over an external range of 1.0–5.0?
About 6.5
35
pH REQUIREMENT classifications
Neutralophiles
Acidophiles
Alkaliphiles
36
What is the optimum pH range for Alkaliphiles?
As high as pH 10.5
37
What is the internal pH maintained by Alkaliphiles over an external range of 9.0–11.0?
About 9.5
38
What substances in media act as buffers for pH control?
Peptones and amino acids
39
What is the buffering effect of phosphate salts useful for?
In the pH growth range of most bacteria
40
To what final pH are culture media for bacterial isolation usually adjusted?
Between 7.0 to 7.5
41
OSMOTIC PRESSURE REQUIREMENT classifications
Osmophilic
Barophiles
Plasmolysis
42
Other physical factors
Salt concentration and Moisture
43
What term describes organisms that require high osmotic pressures?
Osmophilic
44
What term describes the shrinkage of the cell's cytoplasm due to osmotic pressure?
Plasmolysis
45
What are organisms that grow rapidly in high-pressure environments (600 to 1100 atm) called?
Barophiles
46
Name an example of a Barophile.
Shewanella, Colwellia, Photobacterium
47
What term describes organisms that require high salt concentrations?
Halophilic
48
Name an example of a Halophilic organism.
Staphylococcus aureus, Listeria monocytogenes
49
Which Vibrio species are exceptions to the general rule for Halophilic organisms?
Vibrio mimicus and Vibrio cholerae
50
What term describes organisms that require high salt concentrations for growth?
Extreme Halophiles/Obligate Halophiles
51
What term describes organisms that can grow at salt concentrations up to 2% but do not require high salt concentrations?
Facultative Halophiles
52
What is vital for bacterial growth and susceptibility testing?
Moisture
53
Bacteria have three major nutritional needs for growth:
Source of Carbon
Source of Nitrogen
Source of Energy
54
What percentage of a bacterium's dry weight is carbon?
50%
55
Primary role of carbon in bacteria
making cellular constituents
56
What percentage of the dry weight of a bacterium is nitrogen?
14%
57
What is the primary role of nitrogen in bacteria?
Making proteins
58
What is the primary source of energy for bacterial cellular functions?
ATP
59
What role does phosphate play in bacterial cells?
Nucleic acids and phospholipids of cell membranes
60
What role does sulfur play in bacterial cells?
Protein synthesis
61
What percentage of a bacterium's weight is made up by phosphate and sulfur combined?
4%
62
Name some mineral ions important for bacterial growth.
Na+, K+, Cl−, and Ca
63
2 types of microorganisms that utilize carbon
Heterotrophs
Autotrophs
64
Heterotrophs example
Chemoheterotrophs
65
Autotrophs example
Chemoautotrophs, Photoautotrophs
Chemolithotrophs
66
What do heterotrophs (organotrophs) require for growth?
Organic carbon
67
require organic carbon for growth
Use reduced, preformed, organic molecules from other bacteria
Heterothrophs (Organotrophs)
68
get most of their carbon from the source of their energy- proteins, carbohydrates, and lipids
Chemoheterotrophs
69
Use CO2 as the sole source of carbon
do not require organic nutrients for growth
Autotrophs (Litotrophs)
70
What do chemolithotrophs use as a reductant and carbon source?
An inorganic substrate (e.g., hydrogen or thiosulfate) as a reductant and carbon dioxide as a carbon source
71
derive their carbon from carbon dioxide
Chemoautotrophs and Photoautotrophs
72
use an inorganic substrate such as hydrogen or thiosulfate as a reductant and carbon dioxide as a carbon source
Chemolithotrophs
73
What is the sole nitrogen source for some bacteria?
NH3
74
What process allows bacteria to assimilate N2 reductively via NH3?
Nitrogen Fixation
75
What is the process of producing NH3 from the deamination of amino acids?
Ammonification
76
What term describes the ability to assimilate nitrate (NO3-) and nitrite (NO2-) reductively?
Assimilatory nitrate reduction and assimilatory nitrite reduction
77
What process converts NH3 to gaseous N2 under anaerobic conditions?
Denitrification
78
What component is crucial for ATP, nucleic acids, and coenzymes like NAD and NADP?
Phosphate
79
What process can autotrophic bacteria use to oxidize sulfur to sulfate?
Sulfate reduction
80
What can most microorganisms use as a sulfur source, reducing it to hydrogen sulfide (H2S)?
Sulfate
81
What term describes the direct assimilation of H2S from the growth medium?
H2S assimilation
82
What are common sources of sulfur for microorganisms?
Sulfate ion, hydrogen sulfide, sulfur-containing amino acids
83
What ions are essential for enzyme function?
Magnesium Ion (Mg2+) and Ferrous Ion (Fe2+)
84
Which ions are important for the function and integrity of ribosomes?
Mg2+ and K+
85
What ion is a constituent of gram-positive cell walls?
Ca2+
86
What are other important minerals for bacteria?
Mn2+, Mo2+, Co2+, Cu2+, and Zn2+
87
What term describes organic compounds that a cell must obtain to grow but cannot synthesize?
Growth Factors
88
What term describes bacteria that require additional substances such as vitamins and purines for growth?
Fastidious bacteria
89
What term describes bacteria that do not require exogenous growth factors because they synthesize their own?
Prototrophics
90
What term describes bacteria that require the addition of growth factors to the culture media for growth?
Auxotrophics
91
What term describes bacteria that require dead organic substances for growth?
Saprophytes
92
All bacteria that inhabit the human body fall into the _____________ group
heterotrophic or organotrophic
93
Growth Factors Example:
Amino Acids,
Purines,
Pyrimidines and Vitamins, Hemoglobin,
Pentose,
Fatty Acids
94
What term describes organisms that grow in the presence of atmospheric oxygen?
Aerobes
95
What term describes organisms that require 21% oxygen and 0.03% CO2 for growth?
Obligate Aerobes
96
What example bacteria are classified as obligate aerobes?
Bordetella, Brucella, Mycobacteria, Pseudomonas
97
What term describes organisms that can use oxygen but can continue growth by fermentation or anaerobic respiration when oxygen is absent?
Facultative Anaerobes
98
What example bacteria are classified as facultative anaerobes?
Enterobacteriaceae
99
What term describes organisms that require a reduced level of oxygen to grow, specifically 2%-10% oxygen?
Microaerophiles
100
What is the typical microaerophilic atmosphere composition used to grow microaerophiles?
5% O2, 10% CO2, 85% N2
101
What example bacteria are classified as microaerophiles?
Campylobacter spp., Treponema pallidum
102
What term describes organisms that grow in the absence of atmospheric oxygen?
Anaerobes
103
What term describes bacteria that are unable to use molecular oxygen for energy-yielding reactions and lack both superoxide dismutase and catalase?
Obligate Anaerobes
104
What is the typical atmospheric composition for obligate anaerobes?
0% O2, 5-10% CO2, 80-90% N2, 5-10% H2
105
What example bacteria are classified as obligate anaerobes?
Clostridium, Bacteroides
106
What term describes bacteria that can grow in the presence of oxygen but do not use it as a hydrogen acceptor and ferment carbohydrates to lactic acid?
Aerotolerant Anaerobes (Facultative Anaerobes)
107
What example bacteria are classified as aerotolerant anaerobes?
Lactobacilli, Propionibacterium acnes
108
What is an example of a reducing agent used to create anaerobic conditions?
Thioglycolate
109
What are two methods to maintain anaerobic conditions in culture vessels?
Sealing with petrolatum and paraffin; removing oxygen by evacuation or chemical
110
What equipment can be used to handle organisms in anaerobic conditions?
Anaerobic glove box
111
What two enzymes do obligate aerobes and facultative anaerobes contain to counteract the toxic effects of oxygen?
Superoxide dismutase and Catalase
112
What term describes organisms that grow best in an atmosphere enriched with extra carbon dioxide?
Capnophilic
113
What is the optimal atmospheric composition for capnophilic organisms?
15% O2, 5-10% CO2
114
What method provides 3% CO2 for capnophilic organisms?
Candle jars
115
What example bacteria are classified as capnophilic?
HACEK, Neisseria gonorrhoeae
116
At what CO2 level are aerobic incubators often maintained in diagnostic microbiology laboratories?
5-10% CO2
117
What is the CO2 requirement for most aerobic and facultative aerobic bacteria?
0.03% CO2
118
What term describes the time required for one cell to divide into two cells?
Generation Time (Doubling Time)
119
What is the generation time for a slow-growing bacterium like Mycobacterium tuberculosis?
24 hours
120
What are the four phases of bacterial growth?
Lag phase, Log phase, Stationary phase, Death phase
121
During which phase of bacterial growth do bacteria prepare to divide?
Lag phase
122
During which phase do bacteria numbers increase logarithmically?
Log phase
123
During which phase do nutrients become limited and the number of bacteria remains constant?
Stationary phase
124
During which phase does the number of nonviable bacterial cells exceed the number of viable cells?
Death phase
125
What phase of bacterial growth is also known as the adjustment phase?
Lag Phase
126
What characterizes the metabolic activity during the lag phase?
Intense metabolic activity involving the synthesis of enzymes and molecules
127
Is there significant cell division during the lag phase?
No, there is little or no cell division.
128
What is another name for the log phase?
Exponential Phase
129
During which phase is cellular reproduction most active and generation time reaches a minimum?
Log Phase
130
In which phase are cells most active metabolically?
Log Phase
131
In which growth phase are microorganisms most susceptible to antibiotics?
Log Phase
132
What are the two factors that can cause the log phase to end?
Exhaustion of nutrients or accumulation of toxic metabolic products
133
What phase is referred to as the phase of equilibrium or plateau phase?
Stationary Phase
134
What happens to the growth rate and number of deaths during the stationary phase?
The growth rate slows, and the number of deaths balances the number of new cells.
135
What happens to metabolic activity in the stationary phase?
It slows down.
136
What causes the stationary phase?
Nutrient exhaustion, accumulation of toxic products, and harmful changes in pH.
137
What is another name for the death phase?
Logarithmic Decline Phase
138
What happens to the population during the death phase?
The number of deaths exceeds the number of new cells, leading to a population decline.
139
What are the reasons for the bacterial decline during the death phase?
Loss of nutrients and accumulation of toxic waste.
140
Does the total bacterial count decrease in the death phase?
No, only the number of viable organisms decreases, not the total count
141
DETERMINATION OF CELL NUMBERS
1. Direct counting under the microscope
2. Direct plate count
3. Density measurement
142
Direct Measurement of Microbial Growth
a. Plate Counts
b. Filtration
c. Most Probable Number (MPN) Method
143
Estimating Bacterial Numbers by Indirect Methods
a. Turbidity
b. Metabolic Activity
c. Dry Weight
144
Which method of cell number determination estimates the total number of bacteria but does not distinguish between live and dead cells?
Direct counting under the microscope
145
What method involves dilutions of broth cultures on agar plates to count viable cells?
Direct plate count
146
What unit is used to express bacterial counts in the direct plate count method?
Colony-forming units per milliliter (CFU/mL)
147
Which method is commonly used to determine bacterial cell counts in urine cultures?
Direct plate count
148
Which method correlates to CFU/mL and is used to prepare a standard inoculum for antimicrobial susceptibility testing?
Density measurement
149
What method measures the number of viable cells and is often reported as colony-forming units?
Plate counts
150
What technique is used in plate counts to reduce the concentration of bacteria for counting?
Serial dilutions
151
What plate count method introduces 1.0 ml or 0.1 ml of bacterial suspension into a Petri dish?
Pour plates
152
What method spreads 0.1 ml of inoculum uniformly over the surface of a prepoured agar medium?
Spread plates
153
What method passes water through a membrane filter to detect and enumerate coliform bacteria?
Filtration
154
Which statistical estimating technique is based on the dilution needed to eliminate bacterial growth?
Most probable number (MPN) method
155
What method places a measured volume of a bacterial suspension on a microscope slide to count bacteria?
Direct microscopic count
156
What tool is used in direct microscopic counts?
Petroff-Hausser cell counter
157
What indirect method of estimating bacterial numbers uses a spectrophotometer?
Turbidity
158
What method uses McFarland Standards and the nephelometric method for bacterial estimation?
Turbidity
159
Which indirect method of estimating bacterial numbers is based on the production of metabolic products?
Metabolic activity
160
What indirect method estimates bacterial numbers by measuring dry weight?
Dry weight
161
What standards and methods do we use to measure turbidity
McFarland Standards
nephelometric method
