_________________ - defined not as increase in cell size, but increase in numbers of cells
- Microbial growth
__________ (parental cell) - a cell that will divide to produce two daughter cells
- mother cell
_____________ (Fig 6.1) - the process of cell division in most microorganisms. Replicated DNAs are attached to the cell membrane, and separate during growth. A transverse septum composed of cell membrane and cell wall separates the cell into two. Incomple
- Binary fission
___________ (Fig 6.2) - the process of cell division in yeasts and a few bacteria.
- budding
_________- a mixture of substances on which microorganisms grow.
- medium (pl. media)
A standard bacterial growth curve (Fig 6.3, a logarithmic plot) has four phases:
1) ___________ - the period of time in which organisms are not reproducing, but are growing,
actively synthesizing enzymes and other necessary components
2) _________________
- lag phase
- Log phase
- stationary phase
- death phase
In colonies, cells in the _______ of the colony may be in stationary or death phase while cells at the ________ are in log phase.
- middle
- edges
Measuring bacterial growth
1) _____________ (Fig 6.6) - a series of 1:10 dilutions are made from a liquid culture (i.e., I
ml of culture + 9 ml of liquid). From one or more dilutions, samples are transferred to agar medium one of two ways:
i) ___________
- Serial dilution
- pour plate
Measuring bacterial growth
ii) ___________ - samples of one or more dilutions are spread on the surface of agar
plates.
Plates that contain ________ colonies are countable Fig 6.8):
Less than _____ colonies yield statistically insignificant results.
Great
- spread plate
- 30 to 300
- 30
- 300
Measuring bacterial growth:
If the original culture contains 2 x 106 living cells per ml:
1 ml of a 1:10 dilution would yield 2 x 105 colonies
1 ml of a 1:100 dilution would yield 2 x 104 colonies
1 ml of a 1:1000 dilution would yield 2 x 103 colonies
0.1
- 1:1000
- 200
Measuring bacterial growth:
2) ______________ (Fig 6.9) - a known volume of culture is put in a Petroff-Hauser
counting chamber, a calibrated microscope slide. The counting chamber is marked with a grid of known volumes. The operator counts several of the
- direct microscopic count
Measuring bacterial growth:
3) ___________________ (MPN, Fig 6.10, Table 6.1) - used to estimate the number of
organisms in a sample when there are too few to count. A set of dilutions is made, and several tubes of each dilution are incubated. With enough
- most probable number
Measuring bacterial growth:
4) ___________ - used to estimate the number of organisms in a sample when there are only a few present. A large volume of culture is filtered through a filter small enough to capture the organisms, then the filter is incubated
- filtration
Measuring bacterial growth:
5) __________ (Fig 6.11, 6.12) - the ability of a liquid culture to block transmitted light is
assessed using a colorimeter or a spectrophotometer. Cultures with high cell density must be diluted to get an accurate reading, and
- turbidity
Measuring bacterial growth:
6) measurement of ___________:
i) ___________ can be assessed by adding a small inverted test tube (a Durham tube)
to a culture to capture gas as a bubble.
ii) ____________ can be assessed by adding an acid-base indicator dye t
- metabolism
- Gas production
- Acid production
- Utilization of oxygen
Measuring bacterial growth:
7) ___________ - estimates the total cellular mass in a culture. Does not distinguish between
live and dead cells.
- dry weight
Factors affecting bacterial growth:
_______________ - pH, temperature, oxygen concentration, moisture, hydrostatic pressure,
osmotic pressure, radiation
________________ - availability of usable forms of carbon, nitrogen, sulfur, phosphorus, trace element
- physical factors
- Nutritional (biochemical) factors
Factors affecting bacterial growth:
pH:
Most microorganisms have an optimum pH (the pH at which they grow best) near _____.
Most microorganisms will not grow more than _____ pH unit above or below their optimum.
- 7.0
- one
Factors affecting bacterial growth:
____________ - "acid lovers" grow best at pH 0.1 to 5.4, depending on the specific organism.
Lactobacillus tolerates moderately low pH.
Organisms that oxidize sulfur to sulfuric acid, may tolerate much lower p
- acidophiles
Factors affecting bacterial growth:
____________ - grow best at pH 5.4 to 8.0. Most bacteria that cause disease fall into this \ group.
- neutrophiles
Factors affecting bacterial growth:
___________ - "alkali lovers" grow best at pH 7.0 to 11.5.
Vibrio cholerae, which causes Asian cholera, grows best at pH 9.0
Alcaligenes faecalis, an opportunistic pathogen, grows best at pH 9.0 of higher
Agro
- alkaliphiles
Factors affecting bacterial growth:
Accumulation of organic acids may cause ___________ of proteins. Organinc acids may themselves be toxic, apart from their effect on lowering pH. Some cell walls limit exposure to pH extremes.
- denaturation
Factors affecting bacterial growth:
Temperature:
Most microorganisms can grow over a range of ~_______.
- 30 celcius
Factors affecting bacterial growth:
_____________ - "cold lovers" grow best at 15�C.to 20�C. Live mostly in cold water and soil,
and are responsible for spoilage of refrigerated food.
________ - means the organism must have the specified conditi
- psychrophiles
- obligate
- facultative
- obligate
- facultative
Factors affecting bacterial growth:
____________ - grow best at 25�C.to 40�C. Includes human pathogens
Thermoduric organisms live as mesophiles ordinarily, but can tolerate short periods of
high temperature, and may survive if pasteurization or canning me
- Mesophiles
Factors affecting bacterial growth:
____________ - "heat lovers" grow best at 50�C.to 60�C.
________ thermophiles - can grow only above 37�C.
________ thermophiles - can grow above or below 37�C
Bacillus stearothermophilus grows best at 65�C.to
- thermophiles
- obligate
- facultative
Factors affecting bacterial growth:
The temperature at which an organism will grow depends on the functioning of its ________ (Fig 6.14).
minimum growth temperature - lowest temperature at which cells can divide
maximum growth temperature - highest temper
- enzymes
Factors affecting bacterial growth:
Freezing usually prevents bacterial growth, but does not necessarily _____ the bacteria.
- kill
Factors affecting bacterial growth:
High temperatures usually prevent bacterial growth by ______________ essential bacterial proteins.
- permanently denaturing
Factors affecting bacterial growth:
Some _____________ grow better under ice and snow in the winter than they do in the summer.
- mountain fungi
Factors affecting bacterial growth:
Oxygen (Fig 6.15):
____________ - require oxygen
Pseudomonas, a source of nosocomial (hospital-acquired) infections
- obligate aerobes
Factors affecting bacterial growth:
__________ anaerobes - do not use oxygen, and are killed by oxygen
Bacteroides, a major component of the intestinal flora
- obligate
Factors affecting bacterial growth:
Oxygen is often the ___________ for growth of aerobes. Oxygen can be increased by shaking cultures during growth, or bubbling air through them.
- limiting factor
Factors affecting bacterial growth:
______________ - grow best when the oxygen level is less than found in the atmosphere.
Campylobacter, also a capnophile - "carbon dioxide loving"
- microaerophiles
Factors affecting bacterial growth:
_________________ - will use oxygen for respiration, if it is available, but can switch to
anaerobic metabolism when oxygen is not available.
Staphylococcus, Escherichia coli often found in intestinal tract and urinary
- facultative anaerobes
Factors affecting bacterial growth:
___________ anaerobes - do not use oxygen, but are not harmed by it.
Lactobacillus always obtains energy by fermentation.
- Aerotolerant
Factors affecting bacterial growth:
Obligate anaerobes are killed by ___________ (O2-), which is formed by some oxidative enzymes. Superoxide is converted to oxygen and toxic peroxide (H2O2) by _________________ enzyme. Catalase enzyme converts peroxide i
- superoxide
- superoxide dismutase
Factors affecting bacterial growth:
Moisture:
No microorganism can survive without water more than a ___________, except endospores.
- few hours
Factors affecting bacterial growth:
_______________ - pressure exerted by water in proportion to depth. Doubles for every 10 m of depth. At 7000 m, some bacteria can survive.
_____________ - microorganisms that live at high pressures, but die at atmospher
- Hydrostatic pressure
- Barophiles
Factors affecting bacterial growth:
______________ - Determines whether cells will gain or lose water by osmosis
_____________ - shrinkage of cells in hyperosmotic environments. Allows preservation of
foods using high concentrations of sugar or salt.
____
- Osmotic pressure
- Plasmolysis
- Halophiles
Factors affecting bacterial growth:
Radiation:
Gamma rays and ultraviolet light can damage DNA and kill organisms.
Some have _________ to protect the cells.
Some have very efficient DNA repair ___________.
- pigments
- enzymes
Factors affecting bacterial growth:
Nutritional Factors:
Microorganisms require carbon, nitrogen, sulfur, phosphorus, trace elements, vitamins. Many can be easily supplied with simple nutrients, but some are:
__________ organisms - those with special nutr
- fastidious
Factors affecting bacterial growth:
Carbon sources:
_____________ - reduce CO2 to glucose, and other organic molecules
Autotrophs and heterotrophs - obtain energy from glucose by glycolysis, fermentation, and the Krebs cycle, and they synthesize other com
- photoautotrophs
Factors affecting bacterial growth:
Nitrogen sources:
Nitrogen is needed to synthesize proteins, nucleotides, and nucleic acids.
Some microorganisms use inorganic nitrogen.
A few microorganisms obtain energy by oxidizing inorganic nitrogen compounds.
Many
- nitrate
- amino
Factors affecting bacterial growth:
Sulfur and phosphorus:
Microorganisms obtain sulfur from sulfates and from sulfur-containing amino acids.
Some microorganisms synthesize sulfur-containing amino acids from inorganic sulfur and other amino acids.
Microor
- ATP
- phospholipids
- nucleic acids
Factors affecting bacterial growth:
Vitamins:
Act as __________.
Intestinal bacteria produce vitamin K and B vitamins for their host.
- coenzymes
Factors affecting bacterial growth:
Nutritional ___________ - the number of nutrients an organism needs to grow.
Those with many enzymes need few nutrients.
- complexity
Factors affecting bacterial growth:
____________ - act within the cell
__________ - act outside the cell. Most exoenzymes are hydrolases that break
macromolecules down into smaller bits, and include:
__________ enzymes - produced by Gram-positive organism
- endoenzymes
- exoenzymes
- extracellular
- periplasmic
Factors affecting bacterial growth:
Adaptations to limited nutrients:
1) ___________ enzymes needed for uptake and metabolism of limited nutrients
2) ___________ enzymes needed for utilization of alternate nutrients
3) Adjust rate of ________ to nutrient
- increase
- synthesize
- growth
Factors affecting bacterial growth:
____________ (Fig 6.17) - formation of endospores in Bacillus, Clostridium and a few other organisms in response to harsh conditions. Occurs in stationary phase, when nutrients are limiting, and/or wastes have accumulat
- Sporulation
_________________ - defined not as increase in cell size, but increase in numbers of cells
- Microbial growth
__________ (parental cell) - a cell that will divide to produce two daughter cells
- mother cell
_____________ (Fig 6.1) - the process of cell division in most microorganisms. Replicated DNAs are attached to the cell membrane, and separate during growth. A transverse septum composed of cell membrane and cell wall separates the cell into two. Incomple
- Binary fission
___________ (Fig 6.2) - the process of cell division in yeasts and a few bacteria.
- budding
_________- a mixture of substances on which microorganisms grow.
- medium (pl. media)
A standard bacterial growth curve (Fig 6.3, a logarithmic plot) has four phases:
1) ___________ - the period of time in which organisms are not reproducing, but are growing,
actively synthesizing enzymes and other necessary components
2) _________________
- lag phase
- Log phase
- stationary phase
- death phase
In colonies, cells in the _______ of the colony may be in stationary or death phase while cells at the ________ are in log phase.
- middle
- edges
Measuring bacterial growth
1) _____________ (Fig 6.6) - a series of 1:10 dilutions are made from a liquid culture (i.e., I
ml of culture + 9 ml of liquid). From one or more dilutions, samples are transferred to agar medium one of two ways:
i) ___________
- Serial dilution
- pour plate
Measuring bacterial growth
ii) ___________ - samples of one or more dilutions are spread on the surface of agar
plates.
Plates that contain ________ colonies are countable Fig 6.8):
Less than _____ colonies yield statistically insignificant results.
Great
- spread plate
- 30 to 300
- 30
- 300
Measuring bacterial growth:
If the original culture contains 2 x 106 living cells per ml:
1 ml of a 1:10 dilution would yield 2 x 105 colonies
1 ml of a 1:100 dilution would yield 2 x 104 colonies
1 ml of a 1:1000 dilution would yield 2 x 103 colonies
0.1
- 1:1000
- 200
Measuring bacterial growth:
2) ______________ (Fig 6.9) - a known volume of culture is put in a Petroff-Hauser
counting chamber, a calibrated microscope slide. The counting chamber is marked with a grid of known volumes. The operator counts several of the
- direct microscopic count
Measuring bacterial growth:
3) ___________________ (MPN, Fig 6.10, Table 6.1) - used to estimate the number of
organisms in a sample when there are too few to count. A set of dilutions is made, and several tubes of each dilution are incubated. With enough
- most probable number
Measuring bacterial growth:
4) ___________ - used to estimate the number of organisms in a sample when there are only a few present. A large volume of culture is filtered through a filter small enough to capture the organisms, then the filter is incubated
- filtration
Measuring bacterial growth:
5) __________ (Fig 6.11, 6.12) - the ability of a liquid culture to block transmitted light is
assessed using a colorimeter or a spectrophotometer. Cultures with high cell density must be diluted to get an accurate reading, and
- turbidity
Measuring bacterial growth:
6) measurement of ___________:
i) ___________ can be assessed by adding a small inverted test tube (a Durham tube)
to a culture to capture gas as a bubble.
ii) ____________ can be assessed by adding an acid-base indicator dye t
- metabolism
- Gas production
- Acid production
- Utilization of oxygen
Measuring bacterial growth:
7) ___________ - estimates the total cellular mass in a culture. Does not distinguish between
live and dead cells.
- dry weight
Factors affecting bacterial growth:
_______________ - pH, temperature, oxygen concentration, moisture, hydrostatic pressure,
osmotic pressure, radiation
________________ - availability of usable forms of carbon, nitrogen, sulfur, phosphorus, trace element
- physical factors
- Nutritional (biochemical) factors
Factors affecting bacterial growth:
pH:
Most microorganisms have an optimum pH (the pH at which they grow best) near _____.
Most microorganisms will not grow more than _____ pH unit above or below their optimum.
- 7.0
- one
Factors affecting bacterial growth:
____________ - "acid lovers" grow best at pH 0.1 to 5.4, depending on the specific organism.
Lactobacillus tolerates moderately low pH.
Organisms that oxidize sulfur to sulfuric acid, may tolerate much lower p
- acidophiles
Factors affecting bacterial growth:
____________ - grow best at pH 5.4 to 8.0. Most bacteria that cause disease fall into this \ group.
- neutrophiles
Factors affecting bacterial growth:
___________ - "alkali lovers" grow best at pH 7.0 to 11.5.
Vibrio cholerae, which causes Asian cholera, grows best at pH 9.0
Alcaligenes faecalis, an opportunistic pathogen, grows best at pH 9.0 of higher
Agro
- alkaliphiles
Factors affecting bacterial growth:
Accumulation of organic acids may cause ___________ of proteins. Organinc acids may themselves be toxic, apart from their effect on lowering pH. Some cell walls limit exposure to pH extremes.
- denaturation
Factors affecting bacterial growth:
Temperature:
Most microorganisms can grow over a range of ~_______.
- 30 celcius
Factors affecting bacterial growth:
_____________ - "cold lovers" grow best at 15�C.to 20�C. Live mostly in cold water and soil,
and are responsible for spoilage of refrigerated food.
________ - means the organism must have the specified conditi
- psychrophiles
- obligate
- facultative
- obligate
- facultative
Factors affecting bacterial growth:
____________ - grow best at 25�C.to 40�C. Includes human pathogens
Thermoduric organisms live as mesophiles ordinarily, but can tolerate short periods of
high temperature, and may survive if pasteurization or canning me
- Mesophiles
Factors affecting bacterial growth:
____________ - "heat lovers" grow best at 50�C.to 60�C.
________ thermophiles - can grow only above 37�C.
________ thermophiles - can grow above or below 37�C
Bacillus stearothermophilus grows best at 65�C.to
- thermophiles
- obligate
- facultative
Factors affecting bacterial growth:
The temperature at which an organism will grow depends on the functioning of its ________ (Fig 6.14).
minimum growth temperature - lowest temperature at which cells can divide
maximum growth temperature - highest temper
- enzymes
Factors affecting bacterial growth:
Freezing usually prevents bacterial growth, but does not necessarily _____ the bacteria.
- kill
Factors affecting bacterial growth:
High temperatures usually prevent bacterial growth by ______________ essential bacterial proteins.
- permanently denaturing
Factors affecting bacterial growth:
Some _____________ grow better under ice and snow in the winter than they do in the summer.
- mountain fungi
Factors affecting bacterial growth:
Oxygen (Fig 6.15):
____________ - require oxygen
Pseudomonas, a source of nosocomial (hospital-acquired) infections
- obligate aerobes
Factors affecting bacterial growth:
__________ anaerobes - do not use oxygen, and are killed by oxygen
Bacteroides, a major component of the intestinal flora
- obligate
Factors affecting bacterial growth:
Oxygen is often the ___________ for growth of aerobes. Oxygen can be increased by shaking cultures during growth, or bubbling air through them.
- limiting factor
Factors affecting bacterial growth:
______________ - grow best when the oxygen level is less than found in the atmosphere.
Campylobacter, also a capnophile - "carbon dioxide loving"
- microaerophiles
Factors affecting bacterial growth:
_________________ - will use oxygen for respiration, if it is available, but can switch to
anaerobic metabolism when oxygen is not available.
Staphylococcus, Escherichia coli often found in intestinal tract and urinary
- facultative anaerobes
Factors affecting bacterial growth:
___________ anaerobes - do not use oxygen, but are not harmed by it.
Lactobacillus always obtains energy by fermentation.
- Aerotolerant
Factors affecting bacterial growth:
Obligate anaerobes are killed by ___________ (O2-), which is formed by some oxidative enzymes. Superoxide is converted to oxygen and toxic peroxide (H2O2) by _________________ enzyme. Catalase enzyme converts peroxide i
- superoxide
- superoxide dismutase
Factors affecting bacterial growth:
Moisture:
No microorganism can survive without water more than a ___________, except endospores.
- few hours
Factors affecting bacterial growth:
_______________ - pressure exerted by water in proportion to depth. Doubles for every 10 m of depth. At 7000 m, some bacteria can survive.
_____________ - microorganisms that live at high pressures, but die at atmospher
- Hydrostatic pressure
- Barophiles
Factors affecting bacterial growth:
______________ - Determines whether cells will gain or lose water by osmosis
_____________ - shrinkage of cells in hyperosmotic environments. Allows preservation of
foods using high concentrations of sugar or salt.
____
- Osmotic pressure
- Plasmolysis
- Halophiles
Factors affecting bacterial growth:
Radiation:
Gamma rays and ultraviolet light can damage DNA and kill organisms.
Some have _________ to protect the cells.
Some have very efficient DNA repair ___________.
- pigments
- enzymes
Factors affecting bacterial growth:
Nutritional Factors:
Microorganisms require carbon, nitrogen, sulfur, phosphorus, trace elements, vitamins. Many can be easily supplied with simple nutrients, but some are:
__________ organisms - those with special nutr
- fastidious
Factors affecting bacterial growth:
Carbon sources:
_____________ - reduce CO2 to glucose, and other organic molecules
Autotrophs and heterotrophs - obtain energy from glucose by glycolysis, fermentation, and the Krebs cycle, and they synthesize other com
- photoautotrophs
Factors affecting bacterial growth:
Nitrogen sources:
Nitrogen is needed to synthesize proteins, nucleotides, and nucleic acids.
Some microorganisms use inorganic nitrogen.
A few microorganisms obtain energy by oxidizing inorganic nitrogen compounds.
Many
- nitrate
- amino
Factors affecting bacterial growth:
Sulfur and phosphorus:
Microorganisms obtain sulfur from sulfates and from sulfur-containing amino acids.
Some microorganisms synthesize sulfur-containing amino acids from inorganic sulfur and other amino acids.
Microor
- ATP
- phospholipids
- nucleic acids
Factors affecting bacterial growth:
Vitamins:
Act as __________.
Intestinal bacteria produce vitamin K and B vitamins for their host.
- coenzymes
Factors affecting bacterial growth:
Nutritional ___________ - the number of nutrients an organism needs to grow.
Those with many enzymes need few nutrients.
- complexity
Factors affecting bacterial growth:
____________ - act within the cell
__________ - act outside the cell. Most exoenzymes are hydrolases that break
macromolecules down into smaller bits, and include:
__________ enzymes - produced by Gram-positive organism
- endoenzymes
- exoenzymes
- extracellular
- periplasmic
Factors affecting bacterial growth:
Adaptations to limited nutrients:
1) ___________ enzymes needed for uptake and metabolism of limited nutrients
2) ___________ enzymes needed for utilization of alternate nutrients
3) Adjust rate of ________ to nutrient
- increase
- synthesize
- growth
Factors affecting bacterial growth:
____________ (Fig 6.17) - formation of endospores in Bacillus, Clostridium and a few other organisms in response to harsh conditions. Occurs in stationary phase, when nutrients are limiting, and/or wastes have accumulat
- Sporulation