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BACTERIOLOGY - LEC > C5 - Microbial Growth and Nutrition > Flashcards

C5 - Microbial Growth and Nutrition Flashcards

1
Q

What are the two main categories of requirements for microbial growth?

A

Physical and Chemical

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2
Q

What physical factors are required for microbial growth?

A

Temperature, pH, and osmotic pressure

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3
Q

What chemical factors are necessary for microbial growth?

A

Sources of carbon, nitrogen, sulfur, phosphorus, oxygen, trace elements, and organic growth factors

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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

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5
Q

What are cold-loving microbes that grow well between 0°C and 20°C called?

A

Psychrophiles/Cryophiles

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6
Q

What is an example of a psychrophile?

A

Listeria monocytogenes
Yersinia enterolitica

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7
Q

What temperature range do psychrotrophs prefer?

A

Optimum between 20°C and 30°C but can grow well at lower temperatures

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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

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9
Q

temperature optimum between 20°C and 30°C but grow well at lower temperatures
important cause of food spoilage

A

Psychrotrophs

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10
Q

What is an example of a mesophile commonly encountered in clinical laboratories?

A

pathogenic bacteria

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11
Q

What are heat-loving microbes that grow best at temperatures between 50°C and 60°C called?

A

Thermophiles

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12
Q

Name an example of a thermophile.

A

Bacillus stearothermophilus

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13
Q

What term describes microbes that can survive temperatures above the boiling point of water?

A

Hyperthermophilic

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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

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15
Q

What temperature range do psychrophiles/Cryophiles grow well in?

A

0°C to a maximum of 20°C

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16
Q

What is the temperature range that psychrotrophs grow optimally in?

A

20°C to 30°C

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17
Q

At what temperature range do mesophiles grow?

A

20°C to 40°C

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18
Q

What is the optimal temperature range for mesophiles?

A

30°C to 37°C

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19
Q

What temperature range do thermophiles prefer?

A

50°C to 60°C

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20
Q

What temperature range can hyperthermophilic microbes survive in?

A

Above the temperature of boiling water

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21
Q

What temperature range do psychrophiles/Cryophiles thrive in?

A

0°C to 20°C

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22
Q

What is the lowest temperature at which a species will grow called?

A

Minimum Growth Temperature

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23
Q

What is the temperature at which a species grows best called?

A

Optimum Growth Temperature

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24
Q

What is the highest temperature at which growth is possible for a species called?

A

Maximum Growth Temperature

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25
Q

What is the term for the lowest or minimum time required to kill an organism under a constant temperature?

A

Thermal Death Time

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26
Q

What is the lowest temperature required to kill a microorganism in a constant time called?

A

Thermal Death Point

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27
Q

What type of organisms are most commonly found in the temperature range of 30°C (35-37°C)?

A

Mesophilic organisms

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28
Q

At what temperature do diagnostic laboratories usually incubate cultures for bacterial growth?

A

35°C

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29
Q

Which two bacteria can grow at both 35°C and 42°C?

A

Pseudomonas aeruginosa and Campylobacter

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30
Q

What is the pH range where most bacteria grow best?

A

pH 6.5 to 7.5

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31
Q

What pH range do Neutralophiles grow best in?

A

pH 6.0–8.0

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32
Q

What is the internal pH maintained by Neutralophiles over an external range of 5.5–8.5?

A

About 7.5

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33
Q

What is the optimum pH range for Acidophiles?

A

As low as pH 3.0

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34
Q

What is the internal pH maintained by Acidophiles over an external range of 1.0–5.0?

A

About 6.5

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35
Q

pH REQUIREMENT classifications

A

Neutralophiles
Acidophiles
Alkaliphiles

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36
Q

What is the optimum pH range for Alkaliphiles?

A

As high as pH 10.5

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37
Q

What is the internal pH maintained by Alkaliphiles over an external range of 9.0–11.0?

A

About 9.5

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38
Q

What substances in media act as buffers for pH control?

A

Peptones and amino acids

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39
Q

What is the buffering effect of phosphate salts useful for?

A

In the pH growth range of most bacteria

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40
Q

To what final pH are culture media for bacterial isolation usually adjusted?

A

Between 7.0 to 7.5

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41
Q

OSMOTIC PRESSURE REQUIREMENT classifications

A

Osmophilic
Barophiles
Plasmolysis

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42
Q

Other physical factors

A

Salt concentration and Moisture

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43
Q

What term describes organisms that require high osmotic pressures?

A

Osmophilic

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44
Q

What term describes the shrinkage of the cell’s cytoplasm due to osmotic pressure?

A

Plasmolysis

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45
Q

What are organisms that grow rapidly in high-pressure environments (600 to 1100 atm) called?

A

Barophiles

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46
Q

Name an example of a Barophile.

A

Shewanella, Colwellia, Photobacterium

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47
Q

What term describes organisms that require high salt concentrations?

A

Halophilic

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48
Q

Name an example of a Halophilic organism.

A

Staphylococcus aureus, Listeria monocytogenes

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49
Q

Which Vibrio species are exceptions to the general rule for Halophilic organisms?

A

Vibrio mimicus and Vibrio cholerae

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50
Q

What term describes organisms that require high salt concentrations for growth?

A

Extreme Halophiles/Obligate Halophiles

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51
Q

What term describes organisms that can grow at salt concentrations up to 2% but do not require high salt concentrations?

A

Facultative Halophiles

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52
Q

What is vital for bacterial growth and susceptibility testing?

A

Moisture

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53
Q

Bacteria have three major nutritional needs for growth:

A

Source of Carbon
Source of Nitrogen
Source of Energy

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54
Q

What percentage of a bacterium’s dry weight is carbon?

A

50%

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55
Q

Primary role of carbon in bacteria

A

making cellular constituents

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56
Q

What percentage of the dry weight of a bacterium is nitrogen?

A

14%

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57
Q

What is the primary role of nitrogen in bacteria?

A

Making proteins

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58
Q

What is the primary source of energy for bacterial cellular functions?

A

ATP

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59
Q

What role does phosphate play in bacterial cells?

A

Nucleic acids and phospholipids of cell membranes

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60
Q

What role does sulfur play in bacterial cells?

A

Protein synthesis

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61
Q

What percentage of a bacterium’s weight is made up by phosphate and sulfur combined?

A

4%

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62
Q

Name some mineral ions important for bacterial growth.

A

Na+, K+, Cl−, and Ca

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63
Q

2 types of microorganisms that utilize carbon

A

Heterotrophs
Autotrophs

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64
Q

Heterotrophs example

A

Chemoheterotrophs

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65
Q

Autotrophs example

A

Chemoautotrophs, Photoautotrophs
Chemolithotrophs

66
Q

What do heterotrophs (organotrophs) require for growth?

A

Organic carbon

67
Q

require organic carbon for growth
 Use reduced, preformed, organic molecules from other bacteria

A

Heterothrophs (Organotrophs)

68
Q

 get most of their carbon from the source of their energy- proteins, carbohydrates, and lipids

A

Chemoheterotrophs

69
Q

Use CO2 as the sole source of carbon
do not require organic nutrients for growth

A

Autotrophs (Litotrophs)

70
Q

What do chemolithotrophs use as a reductant and carbon source?

A

An inorganic substrate (e.g., hydrogen or thiosulfate) as a reductant and carbon dioxide as a carbon source

71
Q

 derive their carbon from carbon dioxide

A

Chemoautotrophs and Photoautotrophs

72
Q

 use an inorganic substrate such as hydrogen or thiosulfate as a reductant and carbon dioxide as a carbon source

A

Chemolithotrophs

73
Q

What is the sole nitrogen source for some bacteria?

A

NH3

74
Q

What process allows bacteria to assimilate N2 reductively via NH3?

A

Nitrogen Fixation

75
Q

What is the process of producing NH3 from the deamination of amino acids?

A

Ammonification

76
Q

What term describes the ability to assimilate nitrate (NO3-) and nitrite (NO2-) reductively?

A

Assimilatory nitrate reduction and assimilatory nitrite reduction

77
Q

What process converts NH3 to gaseous N2 under anaerobic conditions?

A

Denitrification

78
Q

What component is crucial for ATP, nucleic acids, and coenzymes like NAD and NADP?

A

Phosphate

79
Q

What process can autotrophic bacteria use to oxidize sulfur to sulfate?

A

Sulfate reduction

80
Q

What can most microorganisms use as a sulfur source, reducing it to hydrogen sulfide (H2S)?

A

Sulfate

81
Q

What term describes the direct assimilation of H2S from the growth medium?

A

H2S assimilation

82
Q

What are common sources of sulfur for microorganisms?

A

Sulfate ion, hydrogen sulfide, sulfur-containing amino acids

83
Q

What ions are essential for enzyme function?

A

Magnesium Ion (Mg2+) and Ferrous Ion (Fe2+)

84
Q

Which ions are important for the function and integrity of ribosomes?

A

Mg2+ and K+

85
Q

What ion is a constituent of gram-positive cell walls?

A

Ca2+

86
Q

What are other important minerals for bacteria?

A

Mn2+, Mo2+, Co2+, Cu2+, and Zn2+

87
Q

What term describes organic compounds that a cell must obtain to grow but cannot synthesize?

A

Growth Factors

88
Q

What term describes bacteria that require additional substances such as vitamins and purines for growth?

A

Fastidious bacteria

89
Q

What term describes bacteria that do not require exogenous growth factors because they synthesize their own?

A

Prototrophics

90
Q

What term describes bacteria that require the addition of growth factors to the culture media for growth?

A

Auxotrophics

91
Q

What term describes bacteria that require dead organic substances for growth?

A

Saprophytes

92
Q

All bacteria that inhabit the human body fall into the _____________ group

A

heterotrophic or organotrophic

93
Q

Growth Factors Example:

A

Amino Acids,
Purines,
Pyrimidines and Vitamins, Hemoglobin,
Pentose,
Fatty Acids

94
Q

What term describes organisms that grow in the presence of atmospheric oxygen?

A

Aerobes

95
Q

What term describes organisms that require 21% oxygen and 0.03% CO2 for growth?

A

Obligate Aerobes

96
Q

What example bacteria are classified as obligate aerobes?

A

Bordetella, Brucella, Mycobacteria, Pseudomonas

97
Q

What term describes organisms that can use oxygen but can continue growth by fermentation or anaerobic respiration when oxygen is absent?

A

Facultative Anaerobes

98
Q

What example bacteria are classified as facultative anaerobes?

A

Enterobacteriaceae

99
Q

What term describes organisms that require a reduced level of oxygen to grow, specifically 2%-10% oxygen?

A

Microaerophiles

100
Q

What is the typical microaerophilic atmosphere composition used to grow microaerophiles?

A

5% O2, 10% CO2, 85% N2

101
Q

What example bacteria are classified as microaerophiles?

A

Campylobacter spp., Treponema pallidum

102
Q

What term describes organisms that grow in the absence of atmospheric oxygen?

A

Anaerobes

103
Q

What term describes bacteria that are unable to use molecular oxygen for energy-yielding reactions and lack both superoxide dismutase and catalase?

A

Obligate Anaerobes

104
Q

What is the typical atmospheric composition for obligate anaerobes?

A

0% O2, 5-10% CO2, 80-90% N2, 5-10% H2

105
Q

What example bacteria are classified as obligate anaerobes?

A

Clostridium, Bacteroides

106
Q

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?

A

Aerotolerant Anaerobes (Facultative Anaerobes)

107
Q

What example bacteria are classified as aerotolerant anaerobes?

A

Lactobacilli, Propionibacterium acnes

108
Q

What is an example of a reducing agent used to create anaerobic conditions?

A

Thioglycolate

109
Q

What are two methods to maintain anaerobic conditions in culture vessels?

A

Sealing with petrolatum and paraffin; removing oxygen by evacuation or chemical

110
Q

What equipment can be used to handle organisms in anaerobic conditions?

A

Anaerobic glove box

111
Q

What two enzymes do obligate aerobes and facultative anaerobes contain to counteract the toxic effects of oxygen?

A

Superoxide dismutase and Catalase

112
Q

What term describes organisms that grow best in an atmosphere enriched with extra carbon dioxide?

A

Capnophilic

113
Q

What is the optimal atmospheric composition for capnophilic organisms?

A

15% O2, 5-10% CO2

114
Q

What method provides 3% CO2 for capnophilic organisms?

A

Candle jars

115
Q

What example bacteria are classified as capnophilic?

A

HACEK, Neisseria gonorrhoeae

116
Q

At what CO2 level are aerobic incubators often maintained in diagnostic microbiology laboratories?

A

5-10% CO2

117
Q

What is the CO2 requirement for most aerobic and facultative aerobic bacteria?

A

0.03% CO2

118
Q

What term describes the time required for one cell to divide into two cells?

A

Generation Time (Doubling Time)

119
Q

What is the generation time for a slow-growing bacterium like Mycobacterium tuberculosis?

A

24 hours

120
Q

What are the four phases of bacterial growth?

A

Lag phase, Log phase, Stationary phase, Death phase

121
Q

During which phase of bacterial growth do bacteria prepare to divide?

A

Lag phase

122
Q

During which phase do bacteria numbers increase logarithmically?

A

Log phase

123
Q

During which phase do nutrients become limited and the number of bacteria remains constant?

A

Stationary phase

124
Q

During which phase does the number of nonviable bacterial cells exceed the number of viable cells?

A

Death phase

125
Q

What phase of bacterial growth is also known as the adjustment phase?

A

Lag Phase

126
Q

What characterizes the metabolic activity during the lag phase?

A

Intense metabolic activity involving the synthesis of enzymes and molecules

127
Q

Is there significant cell division during the lag phase?

A

No, there is little or no cell division.

128
Q

What is another name for the log phase?

A

Exponential Phase

129
Q

During which phase is cellular reproduction most active and generation time reaches a minimum?

A

Log Phase

130
Q

In which phase are cells most active metabolically?

A

Log Phase

131
Q

In which growth phase are microorganisms most susceptible to antibiotics?

A

Log Phase

132
Q

What are the two factors that can cause the log phase to end?

A

Exhaustion of nutrients or accumulation of toxic metabolic products

133
Q

What phase is referred to as the phase of equilibrium or plateau phase?

A

Stationary Phase

134
Q

What happens to the growth rate and number of deaths during the stationary phase?

A

The growth rate slows, and the number of deaths balances the number of new cells.

135
Q

What happens to metabolic activity in the stationary phase?

A

It slows down.

136
Q

What causes the stationary phase?

A

Nutrient exhaustion, accumulation of toxic products, and harmful changes in pH.

137
Q

What is another name for the death phase?

A

Logarithmic Decline Phase

138
Q

What happens to the population during the death phase?

A

The number of deaths exceeds the number of new cells, leading to a population decline.

139
Q

What are the reasons for the bacterial decline during the death phase?

A

Loss of nutrients and accumulation of toxic waste.

140
Q

Does the total bacterial count decrease in the death phase?

A

No, only the number of viable organisms decreases, not the total count

141
Q

DETERMINATION OF CELL NUMBERS

A
  1. Direct counting under the microscope
  2. Direct plate count
  3. Density measurement
142
Q

Direct Measurement of Microbial Growth

A

a. Plate Counts
b. Filtration
c. Most Probable Number (MPN) Method

143
Q

Estimating Bacterial Numbers by Indirect Methods

A

a. Turbidity
b. Metabolic Activity
c. Dry Weight

144
Q

Which method of cell number determination estimates the total number of bacteria but does not distinguish between live and dead cells?

A

Direct counting under the microscope

145
Q

What method involves dilutions of broth cultures on agar plates to count viable cells?

A

Direct plate count

146
Q

What unit is used to express bacterial counts in the direct plate count method?

A

Colony-forming units per milliliter (CFU/mL)

147
Q

Which method is commonly used to determine bacterial cell counts in urine cultures?

A

Direct plate count

148
Q

Which method correlates to CFU/mL and is used to prepare a standard inoculum for antimicrobial susceptibility testing?

A

Density measurement

149
Q

What method measures the number of viable cells and is often reported as colony-forming units?

A

Plate counts

150
Q

What technique is used in plate counts to reduce the concentration of bacteria for counting?

A

Serial dilutions

151
Q

What plate count method introduces 1.0 ml or 0.1 ml of bacterial suspension into a Petri dish?

A

Pour plates

152
Q

What method spreads 0.1 ml of inoculum uniformly over the surface of a prepoured agar medium?

A

Spread plates

153
Q

What method passes water through a membrane filter to detect and enumerate coliform bacteria?

A

Filtration

154
Q

Which statistical estimating technique is based on the dilution needed to eliminate bacterial growth?

A

Most probable number (MPN) method

155
Q

What method places a measured volume of a bacterial suspension on a microscope slide to count bacteria?

A

Direct microscopic count

156
Q

What tool is used in direct microscopic counts?

A

Petroff-Hausser cell counter

157
Q

What indirect method of estimating bacterial numbers uses a spectrophotometer?

A

Turbidity

158
Q

What method uses McFarland Standards and the nephelometric method for bacterial estimation?

A

Turbidity

159
Q

Which indirect method of estimating bacterial numbers is based on the production of metabolic products?

A

Metabolic activity

160
Q

What indirect method estimates bacterial numbers by measuring dry weight?

A

Dry weight

161
Q

What standards and methods do we use to measure turbidity

A

McFarland Standards
nephelometric method

BACTERIOLOGY - LEC (14 decks)

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