MICROBIAL GROWTH Flashcards
______
• an increase in the number of cells as a result of cell division
Growth
______
• the ultimate process in the life of a microbial cell
Growth
Microbial cells have a ______ life span and a species is maintaned as a result of continued ______ of its population
finite, growth
______
• cell division following enlargement of a cell to twice its minimum size
Binary fission
______
• the partition that forms between dividing cells
Septum
______
• results from the inward growth of the cytoplasmic membrane and cell wall from opposing directions
Septum
Septum
• septum formation continues until the two daughter cells are ______
pinched off
______
• time required for microbial cells to double in number
Generation time
______
• during cell division, each daughter cell receives a ______ and sufficient ______ of all other cell constituents to exist as an ______ cell
Generation time, chromosome, coples, independent
______
• growth of a microbial population in which cell numbers double within a specific time interval
Exponential growth
Exponential growth
• during exponential growth, the increase in cell number is initially ______ but ______ at a ______ rate
slow, increases, faster
The Mathematics of Exponential Growth
• A relationship exists between the ______ number of cells present in a culture and the number present after a period of ______:
______
initial, exponential growth
N = No2^n
The Mathematics of Exponential Growth
N = No2^n
______ is the final cell number
N
The Mathematics of Exponential Growth
N = No2^n
______ is the initial cell number
No
The Mathematics of Exponential Growth
N = No2^n
______ is the number of generations during the period of exponential growth
n
The Mathematics of Exponential Growth
Generation time (g) of the exponentially growing population is ______
g = t/n
The Mathematics of Exponential Growth
Generation time (g) of the exponentially growing population is g = t/n
______ is the duration of exponential growth
t
The Mathematics of Exponential Growth
Generation time (g) of the exponentially growing population is g = t/n
______ is the number of generations during the period of exponential growth
n
The Microbial Growth Cycle
______: a closed-system microbial culture of fixed volume
Batch culture
The Microbial Growth Cycle
Typical growth curve for population of cells grown in a closed system is characterized by four phases:
- ______
- ______
- ______
- ______
Lag phase
Exponential phase
Stationary phase
Death phase
The Microbial Growth Cycle
______
- Interval between when a culture is inoculated and when growth begins
Lag phase
The Microbial Growth Cycle
______
- Cells in this phase are typically in the healthiest state
Exponential phase
The Microbial Growth Cycle
______
- Growth rate of population is zero
Stationary phase
The Microbial Growth Cycle
______
- Either an essential nutrient is used up or waste product of the organism accumulates in the medium
Stationary phase
The Microbial Growth Cycle
______
- If incubation continues after cells reach stationary phase, the cells will eventually die
Death Phase
______: an open-system microbial culture of fixed volume
Continuous culture
______: most common type of continuous culture device
Chemostat
Continuous Culture: The Chemostat
Chemostat
- Both ______ and ______ of culture can be controlled independently and simultaneously
growth rate, population density
Continuous Culture: The Chemostat
• In a chemostat
- The growth rate is controlled by ______
dilution rate
Continuous Culture: The Chemostat
• In a chemostat
- The growth yield (______) is controlled by the ______
cell number/ml, concentration of the limiting nutrient
In a batch culture, growth conditions are constantly ______; it is impossible to independently ______ both growth parameters
changing, control
Chemostat cultures are sensitive to the ______ and ______
dilution rate, limiting nutrient concentration
Chemostat cultures are sensitive to the dilution rate and limiting nutrient concentration
- At too ______ a dilution rate, the organism is washed out
high
Chemostat cultures are sensitive to the dilution rate and limiting nutrient concentration
- At too ______ a dilution rate, the cells may die from starvation
low
Chemostat cultures are sensitive to the dilution rate and limiting nutrient concentration
- ______ concentration of a limiting nutrient results in greater biomass but same growth rate
Increasing
Measurements of Growth
Microscopic Cell Counts
______
– done by simply observing and enumerating the cells present in a culture or natural sample
Total cell counts
Measurements of Growth
Microscopic Cell Counts
______
– can be performed either on samples dried on slides or on liquid samples
Total cell counts
Measurements of Growth
Microscopic Cell Counts
Total cell counts
– ______ can be stained to increase contrast between cells and their background
dried samples
Measurements of Growth
Microscopic Cell Counts
Total cell counts
– for ______, ______ consists of a grid with squares of known area etched on the surface of a glass slide are used. When the coverslip is placed on the chamber, each square on the grid has a precise ______. The number of cells per unit area of grid can be counted under the microscope, giving a measure of the ______.
liquid samples, counting chambers, volume, number of cells per small chamber volume
Measurements of Growth
Microscopic Cell Counts
______
– a quick and easy way of estimating microbial cell numbers
Total cell counts
Measurements of Growth
Microscopic Counts
• Limitations of microscopic counts
- Cannot distinguish between ______ and ______ cells without special ______
live, dead, stains
Measurements of Growth
Microscopic Counts
• Limitations of microscopic counts
- ______ can be overlooked
Small cells
Measurements of Growth
Microscopic Counts
• Limitations of microscopic counts
- ______ is difficult to achieve
Precision
Measurements of Growth
Microscopic Counts
• Limitations of microscopic counts
- ______ required if a stain is not used
Phase-contrast microscope
Measurements of Growth
Microscopic Counts
• Limitations of microscopic counts
- Cell suspensions of ______ (<______° cells/ml) hard to count
low density, 10
Measurements of Growth
Microscopic Counts
• Limitations of microscopic counts
- ______ need to immobilized
Motile cells
Measurements of Growth
Microscopic Counts
• Limitations of microscopic counts
- ______ in sample can be mistaken for cells
Debris
Measurements of Growth
______
• A second method for enumerating cells in liquid samples
Flow Cytometer
Measurements of Growth
______
- Uses laser beams, fluorescent dyes, and electronics
Flow Cytometer
Measurements of Growth
______: measurement of living, reproducing population
Viable cell counts (plate counts)
Measurements of Growth
Viable Counts
Two main ways to perform plate counts:
• ______
• ______
Spread-plate method
Pour-plate method
Measurements of Growth
Viable Counts
To obtain the appropriate colony number, the sample to be counted should always be ______
diluted
Measurements of Growth
______
______ can be highly unreliable when used to assess total cell numbers of natural samples (e.g., soil and water)
- ______ and ______ target only particular species
Viable Counts, Plate counts, Selective culture media, growth conditions
Measurements of Growth
Viable Cell Counting
______: direct microscopic counts of natural samples reveal far more organisms than those recoverable on plates
The Great Plate Anomaly
Measurements of Growth
Viable Cell Counting
The Great Plate Anomaly: direct microscopic counts of natural samples reveal far more organisms than those recoverable on plates
• Why is this?
- ______ count dead cells whereas ______ do not
- Different organisms may have vastly different requirements for ______
Microscopic methods, viable methods, growth
Measurements of Growth
______ are an indirect, rapid, and useful method of measuring microbial growth
Turbidity measurements
Measurements of Growth
Turbidimetric Methods/Turbidity measurements
- Most often measured with a ______ and measurement referred to as ______
spectrophotometer, optical density
Measurements of Growth
______
- Quick and easy to perform
Turbidity measurements
Measurements of Growth
______
- Typically do not require destruction or significant disturbance of sample
Turbidity measurements
Measurements of Growth
______
- Sometimes problematic (e.g., microbes that form clumps or biofilms in liquid medium)
Turbidity measurements
______ is a major environmental factor controlling microbial growth
Temperature
______: the minimum, optimum, and maximum temperatures at which an organism grows
Cardinal temperatures
Temperature and Microbial Growth
• Effect of Temperature on Growth
Microorganisms can be classified into groups by their growth temperature optima
- ______
- ______
- ______
- ______
Psychrophile
Mesophile
Thermophile
Hyperthermophile
Temperature and Microbial Growth
• Effect of Temperature on Growth
Microorganisms can be classified into groups by their growth temperature optima
- ______: low temperature
Psychrophile
Temperature and Microbial Growth
• Effect of Temperature on Growth
Microorganisms can be classified into groups by their growth temperature optima
- ______: midrange temperature
Mesophile
Temperature and Microbial Growth
• Effect of Temperature on Growth
Microorganisms can be classified into groups by their growth temperature optima
- ______: high temperature
Thermophile
Temperature and Microbial Growth
• Effect of Temperature on Growth
Microorganisms can be classified into groups by their growth temperature optima
- ______: very high temperature
Hyperthermophile
Temperature and Microbial Growth
• Microbial Life in the Cold
______
- Organisms that grow under very hot or very cold conditions
Extremophiles
Temperature and Microbial Growth
• Microbial Life in the Cold
______
- Organisms with cold temperature optima
Psychrophiles
Temperature and Microbial Growth
• Microbial Life in the Cold
______
- Inhabit permanently cold environments
Psychrophiles
Temperature and Microbial Growth
• Microbial Life in the Cold
______
- Organisms that can grow at 0°C but have optima of 20°C to 40°C
Psychrotolerant
Temperature and Microbial Growth
• Microbial Life in the Cold
______
- More widely distributed in nature than psychrophiles
Psychrotolerant
Temperature and Microbial Growth
• Microbial Life in the Cold
______
- Production of enzymes that function optimally in the cold; features that may provide more flexibility
Molecular Adaptations to Psychrophily
Temperature and Microbial Growth
• Microbial Life in the Cold
Molecular Adaptations to Psychrophily
- Production of enzymes that function optimally in the cold; features that may provide more flexibility
• More ______ than ______
a-helices, B-sheets
Temperature and Microbial Growth
• Microbial Life in the Cold
Molecular Adaptations to Psychrophily
- Production of enzymes that function optimally in the cold; features that may provide more flexibility
• More ______ and less ______ amino acids
polar, hydrophobic
Temperature and Microbial Growth
• Microbial Life in the Cold
Molecular Adaptations to Psychrophily
- Production of enzymes that function optimally in the cold; features that may provide more flexibility
• Fewer ______ bonds
weak
Temperature and Microbial Growth
• Microbial Life in the Cold
Molecular Adaptations to Psychrophily
- Production of enzymes that function optimally in the cold; features that may provide more flexibility
• Decreased interactions between ______
protein domains
Temperature and Microbial Growth
• Microbial Life in the Cold
Molecular Adaptations to Psychrophily
- Transport processes function optimally at ______ temperatures
• Modified ______
- High ______ content
low, cytoplasmic membranes, unsaturated fatty acid
Temperature and Microbial Growth
• Microbial Life at High Temperatures
Above -65 °C, only ______ life forms exist
prokaryotic
Temperature and Microbial Growth
• Microbial Life at High Temperatures
______: organisms with growth temperature optima between 45 °C and 80 °C
Thermophiles
Temperature and Microbial Growth
• Microbial Life at High Temperatures
______: organisms with optima greater than 80 °C
Hyperthermophiles
Temperature and Microbial Growth
• Microbial Life at High Temperatures
______
- Inhabit hot environments including boiling hot springs and seafloor hydrothermal vents that can have temperatures in excess of 100 °C
Hyperthermophiles
Temperature and Microbial Growth
• Microbial Life at High Temperatures
Studies of thermal habitats have revealed
- Prokaryotes are able to grow at ______ temperatures than eukaryotes
higher
Temperature and Microbial Growth
• Microbial Life at High Temperatures
Studies of thermal habitats have revealed
- Organisms with the highest temperature optima are ______
Archaea
Temperature and Microbial Growth
• Microbial Life at High Temperatures
Studies of thermal habitats have revealed
- ______ organisms can grow at higher temperatures than ______ organisms
Nonphototrophic, phototrophic
Temperature and Microbial Growth
• Microbial Life at High Temperatures
______
- Enzyme and proteins function optimally at high temperatures; features that provide thermal stability
Molecular Adaptations to Thermophily
Temperature and Microbial Growth
• Microbial Life at High Temperatures
Molecular Adaptations to Thermophily
- Enzyme and proteins function optimally at high temperatures; features that provide thermal stability
• Critical amino acid substitutions in a few locations provide more ______
heat-tolerant folds
Temperature and Microbial Growth
• Microbial Life at High Temperatures
Molecular Adaptations to Thermophily
- Enzyme and proteins function optimally at high temperatures; features that provide thermal stability
• An increased number of ______ bonds between ______ and ______ amino acids resist unfolding in the ______
ionic, basic, acidic, aqueous cytoplasm
Temperature and Microbial Growth
• Microbial Life at High Temperatures
Molecular Adaptations to Thermophily
- Enzyme and proteins function optimally at high temperatures; features that provide thermal stability
• Production of ______ (e.g., di-inositol phophate, diglycerol phosphate) help stabilize proteins
solutes
Temperature and Microbial Growth
• Microbial Life at High Temperatures
Molecular Adaptations to Thermophily
- Modifications in cytoplasmic membranes to ensure heat stability
• ______ have lipids rich in saturated fatty acids
Bacteria
Temperature and Microbial Growth
• Microbial Life at High Temperatures
Molecular Adaptations to Thermophily
- Modifications in cytoplasmic membranes to ensure heat stability
• ______ have lipid monolayer rather than bilayer
Archaea
Other Environmental Factors
Affecting Growth
Acidity and Alkalinity
• The ______ of an environment greatly affects microbial growth
pH
Other Environmental Factors
Affecting Growth
Acidity and Alkalinity
• Some organisms have evolved to grow best at low or high pH, but most organisms grow best between pH 6 and 8 (______)
neutrophiles
Other Environmental Factors
Affecting Growth
Acidity and Alkalinity
______: organisms that grow best at low pH (<6)
Acidophiles
Other Environmental Factors
Affecting Growth
Acidity and Alkalinity
Acidophiles
- Some are ______ acidophiles; membranes destroyed at ______ pH
obligate, neutral
Other Environmental Factors
Affecting Growth
Acidity and Alkalinity
______
- Stability of cytoplasmic membrane critical
Acidophiles
Other Environmental Factors
Affecting Growth
Acidity and Alkalinity
______: organisms that grow best at high pH (>9)
Alkaliphiles
Other Environmental Factors
Affecting Growth
Acidity and Alkalinity
Alkaliphiles
- Some have ______ rather than proton motive force
sodium motive force
Other Environmental Factors
Affecting Growth
• Osmotic Effects on Microbial Growth
Typically, the ______ has a higher solute concentration than the surrounding environment, thus the tendency is for ______ to move into the cell (______)
cytoplasm, water, positive water balance
Other Environmental Factors
Affecting Growth
• Osmotic Effects on Microbial Growth
When a cell is in an environment with a higher external ______, water will flow ______ unless the cell has a mechanism to prevent this
solute concentration, out
Other Environmental Factors
Affecting Growth
• Osmotic Effects on Microbial Growth
______: organisms that grow best at reduced water potential; have a specific requirement for NaCI
Halophiles
Other Environmental Factors
Affecting Growth
• Osmotic Effects on Microbial Growth
______: organisms that require high levels (15-30%) of NaCl for growth
Extreme halophiles
Other Environmental Factors
Affecting Growth
• Osmotic Effects on Microbial Growth
______: organisms that can tolerate some reduction in water activity of environment but generally grow best in the absence of the added solute
Halotolerant
Other Environmental Factors
Affecting Growth
• Osmotic Effects on Microbial Growth
______: organisms that live in environments high in sugar as solute
Osmophiles
Other Environmental Factors
Affecting Growth
• Osmotic Effects on Microbial Growth
______: organisms able to grow in very dry environments
Xerophiles
Other Environmental Factors
Affecting Growth
• Oxygen and Microorganisms
______: require oxygen to live
Aerobes
Other Environmental Factors
Affecting Growth
• Oxygen and Microorganisms
______: do not require oxygen and may even be killed by exposure
Anaerobes
Other Environmental Factors
Affecting Growth
• Oxygen and Microorganisms
______: can live with or without oxygen
Facultative organisms
Other Environmental Factors
Affecting Growth
• Oxygen and Microorganisms
______: can tolerate oxygen and grow in its presence even though they cannot use it
Aerotolerant anaerobes
Other Environmental Factors
Affecting Growth
• Oxygen and Microorganisms
______: can use oxygen only when it is present at levels reduced from that in air
Microaerophiles
Other Environmental Factors
Affecting Growth
• Oxygen and Microorganisms
______
- Complex medium that separates microbes based on oxygen requirements
Thioglycolate broth
Other Environmental Factors
Affecting Growth
• Oxygen and Microorganisms
______
- Reacts with oxygen so oxygen can only penetrate the top of the tube
Thioglycolate broth
Other Environmental Factors
Affecting Growth
• Oxygen and Microorganisms
Special ______ are needed to grow aerobic and anaerobic microorganisms
techniques
Other Environmental Factors
Affecting Growth
• Oxygen and Microorganisms
______: chemicals that may be added to culture media to reduce oxygen (eg, thioglycolate)
Reducing agents
Other Environmental Factors
Affecting Growth
• Toxic Forms of Oxygen
Several toxic forms of oxygen can be formed in the cell:
- Single oxygen
- Superoxide anion
- Hydrogen peroxide
- Hydroxyl radical
Other Environmental Factors
Affecting Growth
• Toxic Forms of Oxygen
Enzymes are present to neutralize most of these toxic oxygen species:
- Catalase
- Peroxidase
- Superoxide dismutase
- Superoxide reductase
