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Environmental Factors
Governing Bacterial Growth
Created @November 9, 2024 4:43 PM
Class Microbiology
LO:
Discuss the various environmental factors influencing bacterial growth,
including essential elements, water, salt/osmolarity, pH, temperature, oxygen
availability
Describe bacterial classification based on growth under various environmental
conditions
Describe how bacterial culture medium considers the aforementioned
environmental growth factors
Environmental Factors Affecting Bacterial Growth
Requires a source of nitrogen, carbon, ions and nutrients
Temperature
Water and salt levels
pH
O2 levels in atmosphere
Essential Elements
Environmental Factors Governing Bacterial Growth 1
, Carbon, oxygen, nitrogen, hydrogen, sulphur, phosphorous, potassium,
magnesium, calcium, iron, sodium and chloride
Lots of bacteria can produce molecules called Siderophores which can
isolate iron from iron stores within the body
Water
80% of cell mass is water
In the grow phase, nutrients and waste products enter the cell. Free
available water is a must
Water diffuses into the cell because cytoplasm has a higher solute
concentration leading to positive water balance
Osmolarity (Salt)
Many bacteria have adapted to sources containing high salt levels like
Halophiles
Halophiles require salt level saturation to be between 2.8M and 6.2 M
Salt can change the structure of proteins and membranes
Extreme halophiles can accumulate potassium leaving them hypertonic
(Osmotic pressure being higher than the surroundings), saturation
levels between 4-7M
Halotolerant bacteria- Able to survive in mediums containing high salt
concentrations
Effect of Ph
Environments contain a pH of 5 or 8/9, most organisms can grow in these
conditions
Acidophiles grow best between 5.5 and 8 pH
Alkalophiles grow best at pH’s 8.5-11
Environmental Factors Governing Bacterial Growth 2
Environmental Factors
Governing Bacterial Growth
Created @November 9, 2024 4:43 PM
Class Microbiology
LO:
Discuss the various environmental factors influencing bacterial growth,
including essential elements, water, salt/osmolarity, pH, temperature, oxygen
availability
Describe bacterial classification based on growth under various environmental
conditions
Describe how bacterial culture medium considers the aforementioned
environmental growth factors
Environmental Factors Affecting Bacterial Growth
Requires a source of nitrogen, carbon, ions and nutrients
Temperature
Water and salt levels
pH
O2 levels in atmosphere
Essential Elements
Environmental Factors Governing Bacterial Growth 1
, Carbon, oxygen, nitrogen, hydrogen, sulphur, phosphorous, potassium,
magnesium, calcium, iron, sodium and chloride
Lots of bacteria can produce molecules called Siderophores which can
isolate iron from iron stores within the body
Water
80% of cell mass is water
In the grow phase, nutrients and waste products enter the cell. Free
available water is a must
Water diffuses into the cell because cytoplasm has a higher solute
concentration leading to positive water balance
Osmolarity (Salt)
Many bacteria have adapted to sources containing high salt levels like
Halophiles
Halophiles require salt level saturation to be between 2.8M and 6.2 M
Salt can change the structure of proteins and membranes
Extreme halophiles can accumulate potassium leaving them hypertonic
(Osmotic pressure being higher than the surroundings), saturation
levels between 4-7M
Halotolerant bacteria- Able to survive in mediums containing high salt
concentrations
Effect of Ph
Environments contain a pH of 5 or 8/9, most organisms can grow in these
conditions
Acidophiles grow best between 5.5 and 8 pH
Alkalophiles grow best at pH’s 8.5-11
Environmental Factors Governing Bacterial Growth 2
