M
MICROBIOLOGY & PARASITOLOGY
C3
MIDTERMS MICROBIAL GROWTH
MICROBIAL GROWTH - Habitat:
- Refers to the increase of number and not the size o Altai, Russia
Colony o Himalayas, Nepal
- Result of microbial growth o Alaska
- Aggregation of cells o Artic, Canada
arising from single parent o Tibet China
- Colonies = hundreds of o Tateyama, Japan
thousands of cells o Patagonia, Chile
- Population = billions of
cells NOTE
Food Spoilage Temperatures
Generation Time
- The time required for growth and reproduction of
bacterial cell
- Doubling
Requirements for Microbial Growth
Physical requirements
o Temperature
o pH
o Osmotic Pressure
Chemical Requirements
o Carbon
o Nitrogen
o Sulfur
o Phosphorous
o Oxygen
o Trace Elements
o Organic Growth Factors
Physical Requirements
Temperature
- Microorganisms are classified into three primary - Low temperatures decrease microbial
groups on the basis of their preferred range of reproduction rates, which is the basic principle
temperature: of refrigeration.
1. Psychrophiles - There are always some exceptions to the
Cold loving temperature responses shown here; for
2. Mesophiles example, certain bacteria grow well at high
Middle loving temperatures that would kill most bacteria,
Moderate temperature loving and a few bacteria can actually grow at
Include most pathogens and common temperatures well below freezing.
spoilage organisms
Best growth: 25C to 45C
Optimum growth: 37C pH
3. Thermophiles - refers to the acidity or alkalinity of a solution
Heat loving - Most bacteria grow best in a narrow pH range
Optimum growth: 50C to 60C near neutrality, between pH 6.5 and 7.5.
Many can’t grow below 45C - Very few bacteria grow at an acidic pH below
o Extreme Thermophiles about pH 4.
Hyperthermophiles - Mold and yeast: pH 5 to 6
70C to 110C
Optimum growth: 80C or higher
Psychrophilic Algae: Chlamydomonas Nivalis
- Watermelon snow
- causes a red tint due to the
carotenoid pigment the cell
contains in order to more
fully protect itself against
intensive light.
- also
helps the cell absorb heat
so it is able to melt the
surrounding snow, Acidity - inhibits most microbial growth and
essentially creating is used frequently for food preservation (e.g.:
its own mini liquid pickling).
environment. Alkalinity - inhibits microbial growth, but not
- is toxic if enough is ingested commonly used for food preservation.
Hannah Adan 1
, M
MICROBIOLOGY & PARASITOLOGY
C3
MIDTERMS MICROBIAL GROWTH
plasmolysis, or shrinkage of the cell’s
cytoplasm
NOTE
Acidic products of bacterial metabolism interfere Cell in Hypotonic
with growth. Buffers can be used to stabilize pH Solution
Low osmotic
Chemical Buffers: pressure that
Peptones and amino acids causes water to
Phosphate salts enter the cell
In most cases cell
1. Acidophiles wall prevents
Acid loving excessive entry of
Grow at very low pH (0.1 to 5.4) water
Lactobacillus produces lactic acid, Microbe may lyse
tolerates mild acidity. or burst if cell wall
2. Neutrophiles is weak (osmotic
Grow at pH 5.4 to 8.5. lysis).
Includes most human pathogens.
3. Alkalinophiles 1. Halophiles
Alkali loving moderate to large salt concentrations.
Grow at alkaline or high pH (7 to 12 or Ocean water contains 3.5% salt
higher) Most bacteria in oceans.
Vibrio cholerae and Alkaligenes 2. Extreme or Obligate Halophiles
faecalis optimal pH 9. Require very high salt concentrations
Soil bacterium Agrobacterium grows at (20 to 30%).
pH 12. Bacteria in Dead Sea, brine vats.
Osmotic Pressure 3. Facultative Halophiles
- Microorganisms obtain almost all their nutrients Do not require high salt concentrations
in solution from the surrounding water so they for growth, but tolerate 2% salt or
require water for growth, and their composition is more.
80–90% water. A few species of facultative halophiles
Cell in isotonic can tolerate even 15% salt.
Solution Chemical Requirements
Under these - Organisms use a variety of nutrients for their
conditions, the energy needs and to build organic molecules and
solute cellular structures.
concentration in - Most common nutrients - those containing
the cell is necessary elements such as Carbon (1/2 of the
equivalent to a dry weight of a prokaryotic cell), Oxygen,
solute nitrogen, and hydrogen.
concentration of 0.85% sodium chloride - Microbes obtain nutrients from variety of sources.
(NaCl) Salmonella Typhimunium Yellow
Cell in Hypertonic - Rocky Mountain Labs NIAID
Solution NIH
the cellular water
passes out through
the plasma
membrane to the
high solute
concentration
If the concentration Carbon
of solutes such as NaCl is higher in the - one of the most important requirements for
surrounding medium than in the cell (the microbial growth is carbon
environment is hypertonic), water tends - the structural backbone of living matter
to leave the cell. - it is needed for all the organic compounds that
The growth of the cell is inhibited as the make up a living cell
plasma membrane pulls away from the - four basic groups of organisms:
cell wall. Thus, the addition of salts (or
other solutes) to a solution, and the
resulting increase in osmotic pressure,
can be used to preserve foods.
o Used to control spoilage and
microbial growth:
Sugar in jelly
Salt on meat
NOTE
This osmotic loss of water causes
Hannah Adan 2
MICROBIOLOGY & PARASITOLOGY
C3
MIDTERMS MICROBIAL GROWTH
MICROBIAL GROWTH - Habitat:
- Refers to the increase of number and not the size o Altai, Russia
Colony o Himalayas, Nepal
- Result of microbial growth o Alaska
- Aggregation of cells o Artic, Canada
arising from single parent o Tibet China
- Colonies = hundreds of o Tateyama, Japan
thousands of cells o Patagonia, Chile
- Population = billions of
cells NOTE
Food Spoilage Temperatures
Generation Time
- The time required for growth and reproduction of
bacterial cell
- Doubling
Requirements for Microbial Growth
Physical requirements
o Temperature
o pH
o Osmotic Pressure
Chemical Requirements
o Carbon
o Nitrogen
o Sulfur
o Phosphorous
o Oxygen
o Trace Elements
o Organic Growth Factors
Physical Requirements
Temperature
- Microorganisms are classified into three primary - Low temperatures decrease microbial
groups on the basis of their preferred range of reproduction rates, which is the basic principle
temperature: of refrigeration.
1. Psychrophiles - There are always some exceptions to the
Cold loving temperature responses shown here; for
2. Mesophiles example, certain bacteria grow well at high
Middle loving temperatures that would kill most bacteria,
Moderate temperature loving and a few bacteria can actually grow at
Include most pathogens and common temperatures well below freezing.
spoilage organisms
Best growth: 25C to 45C
Optimum growth: 37C pH
3. Thermophiles - refers to the acidity or alkalinity of a solution
Heat loving - Most bacteria grow best in a narrow pH range
Optimum growth: 50C to 60C near neutrality, between pH 6.5 and 7.5.
Many can’t grow below 45C - Very few bacteria grow at an acidic pH below
o Extreme Thermophiles about pH 4.
Hyperthermophiles - Mold and yeast: pH 5 to 6
70C to 110C
Optimum growth: 80C or higher
Psychrophilic Algae: Chlamydomonas Nivalis
- Watermelon snow
- causes a red tint due to the
carotenoid pigment the cell
contains in order to more
fully protect itself against
intensive light.
- also
helps the cell absorb heat
so it is able to melt the
surrounding snow, Acidity - inhibits most microbial growth and
essentially creating is used frequently for food preservation (e.g.:
its own mini liquid pickling).
environment. Alkalinity - inhibits microbial growth, but not
- is toxic if enough is ingested commonly used for food preservation.
Hannah Adan 1
, M
MICROBIOLOGY & PARASITOLOGY
C3
MIDTERMS MICROBIAL GROWTH
plasmolysis, or shrinkage of the cell’s
cytoplasm
NOTE
Acidic products of bacterial metabolism interfere Cell in Hypotonic
with growth. Buffers can be used to stabilize pH Solution
Low osmotic
Chemical Buffers: pressure that
Peptones and amino acids causes water to
Phosphate salts enter the cell
In most cases cell
1. Acidophiles wall prevents
Acid loving excessive entry of
Grow at very low pH (0.1 to 5.4) water
Lactobacillus produces lactic acid, Microbe may lyse
tolerates mild acidity. or burst if cell wall
2. Neutrophiles is weak (osmotic
Grow at pH 5.4 to 8.5. lysis).
Includes most human pathogens.
3. Alkalinophiles 1. Halophiles
Alkali loving moderate to large salt concentrations.
Grow at alkaline or high pH (7 to 12 or Ocean water contains 3.5% salt
higher) Most bacteria in oceans.
Vibrio cholerae and Alkaligenes 2. Extreme or Obligate Halophiles
faecalis optimal pH 9. Require very high salt concentrations
Soil bacterium Agrobacterium grows at (20 to 30%).
pH 12. Bacteria in Dead Sea, brine vats.
Osmotic Pressure 3. Facultative Halophiles
- Microorganisms obtain almost all their nutrients Do not require high salt concentrations
in solution from the surrounding water so they for growth, but tolerate 2% salt or
require water for growth, and their composition is more.
80–90% water. A few species of facultative halophiles
Cell in isotonic can tolerate even 15% salt.
Solution Chemical Requirements
Under these - Organisms use a variety of nutrients for their
conditions, the energy needs and to build organic molecules and
solute cellular structures.
concentration in - Most common nutrients - those containing
the cell is necessary elements such as Carbon (1/2 of the
equivalent to a dry weight of a prokaryotic cell), Oxygen,
solute nitrogen, and hydrogen.
concentration of 0.85% sodium chloride - Microbes obtain nutrients from variety of sources.
(NaCl) Salmonella Typhimunium Yellow
Cell in Hypertonic - Rocky Mountain Labs NIAID
Solution NIH
the cellular water
passes out through
the plasma
membrane to the
high solute
concentration
If the concentration Carbon
of solutes such as NaCl is higher in the - one of the most important requirements for
surrounding medium than in the cell (the microbial growth is carbon
environment is hypertonic), water tends - the structural backbone of living matter
to leave the cell. - it is needed for all the organic compounds that
The growth of the cell is inhibited as the make up a living cell
plasma membrane pulls away from the - four basic groups of organisms:
cell wall. Thus, the addition of salts (or
other solutes) to a solution, and the
resulting increase in osmotic pressure,
can be used to preserve foods.
o Used to control spoilage and
microbial growth:
Sugar in jelly
Salt on meat
NOTE
This osmotic loss of water causes
Hannah Adan 2
