Chapter 5 Lec.2.2 Flashcards
Molecular adaptations to psychrophily
Production of enzymes that function optimally in cold.
Transport processes function optimally at low temperature.
Microbial life at high temperatures
Above 65, only prokaryotes exist.
Thermophiles: growth optima between 45-80.
Hyperthermophiles: growth optima above 80.
Studies of thermal habitats have revealed…
Prokaryotes are able to grow at high temps better than eukaryotes.
Archaea have highest temp optima.
Thermophily
Enzyme and proteins function optimally at high temps, features that provide thermal stability.
-Heat tolerant amino acids
-Increased number of ionic bonds.
-Solutes help stabilize proteins.
Modifications to cytoplasmic membrane to ensure heat stability.
Hyperthermophiles and industry
Produce enzymes widely used in industrial microbiology.
-Taq polymerase: PCR
pH
Relative acidity in solution.
Microbial growth at high or low pH
pH greatly affects microbial growth.
Most organisms grow between 6-8.
Microbial growth at high or low pH: Types
Acidophiles- 0-5.5.
Neutrophiles- 5.5-7
Alkaliphiles- 8.5 11.5
Microbial growth at high or low pH: Internal pH and acid tolerance
Most microbes maintain internal environment close to neutral.
-Exchange ions for protons
Acid tolerance response.
-pump protons out of cell.
High Pressure
High hydrostatic pressure.
Barotolerant- adversely affected by pressure.
Barophilic- require or grow in increased pressure.
Water activity (aw)
Ratio of vapor pressure of air in equilibrium with substance or solution to the vapor pressure of pure water.
Solutes and water activity
Water activity
- amount of water available to organisms
- reduced by interaction with solute molecules
- higher solutes –>lower aw
- reduced by adsorption to surface
The dead sea
- Tectonic basin
- lowest point on the surface of the planet - salinity
- One of the saltiest naturally occurring bodies of water. - pH ~6
The dead sea: mostly dead, slightly alive
Believed devoid of life until 1930’s.
Wilkansky, 1936, showed living microorganisms.
Don Juan pond
More salinic than The Dead Sea.
-No life.
Solutions
Isotonic solution -same concentration inside as outside Hypotonic -more concentrated inside the cell Hypertonic -more concentrated outside the cell
Halophiles
Organisms that grow best at reduced water potential, requirement for NaCl.
Extreme halophiles: require high levels.
Halotolerant- reduction in water activity.
Solutes in cytoplasm
Cytoplasm > concentration then surrounding environment.
-water moves into cell
Halophile defense mechanisms: High salinity coping mechanisms.
Two high salinity coping mechanisms
- Organic
- energetically expensive
- does not require protein alteration. - Salt in
- energetically cheap
- requires protein alteration
- Used by all haloarchaea and two lineages of bacteria.
Halophile defense mechanisms
Increasing internal solute concentration by:
- pumping ions from environment into cell.
- synthesis or concentration of solutes.
Similar to Halophiles
Osmophiles: organisms that live in environments high in sugar as solute.
Xerophiles: organisms able to grow in very dry environments.
Oxygen and microorganisms
Aerobes- require oxygen.
Anaerobes- do not require oxygen.
Facultative organisms- can live with or without oxygen.
Aerotolerant anaerobes- can tolerate oxygen and grow in its presence even though they cannot use it.
Microaerophiles- can use oxygen only when it is present at levels reduced from the air.
Thioglycolate broth
Complex medium that separates microbes based on oxygen requirements.
Reacts with oxygen so oxygen can only penetrate top of tube.
Toxic forms of oxygen in cell
Single oxygen
Superoxide anion
hydrogen peroxide
hydroxyl radical
Toxic oxygen enzymes
Catalase
Peroxidase
Superoxide dismutase
