Chapter 5 Flashcards
(32 cards)
What type of physical parameters affect microbial growth?
Temperature, pH, osmotic pressure, oxygen availability, and pressure.
What conditions are characteristic of a ‘normal’ environment?
Moderate temperature (20-40°C), neutral pH (~7), sea-level pressure, and moderate salt concentration (~0.9% NaCl).
What is an extremophile? Why is this somewhat of a misnomer?
Extremophiles are microorganisms that thrive in extreme environments such as high temperatures, high salinity, or extreme pH.
The term is a misnomer because what is ‘extreme’ to humans is normal to these organisms.
What are some reasons we are interested in studying extremophiles?
They provide insights into the limits of life, potential for extraterrestrial life, and applications in biotechnology (e.g., thermostable enzymes for industry).
How does temperature affect microorganisms?
Why are bacteria forced to adapt to these temperature changes?
Temperature influences enzyme activity, membrane fluidity, and overall metabolic function.
Bacteria must adapt because extreme temperatures can denature proteins or slow metabolic reactions.
What does it mean that something has an optimal temperature for growth? Minimum and maximum? What limits growth at certain temperatures?
The optimal temperature is where growth occurs fastest. The minimum and maximum temperatures define the range of viability.
Extreme temperatures can denature proteins, solidify membranes (low temp), or disrupt cellular function.
What is a mesophile? Thermophile? Hyper-thermophile? Psychrophile? Halophile? Barophile? Acidophile? Neutrophile? Alkaliphile?
Mesophile: Grows best at moderate temperatures (15-45°C).
Thermophile: Thrives at high temperatures (45-80°C).
Hyper-thermophile: Thrives at extreme heat (>80°C).
Psychrophile: Grows in cold environments (<15°C).
Halophile: Requires high salt concentrations (>2M NaCl).
Barophile: Thrives under high pressure (deep-sea organisms).
Acidophile: Grows best in acidic environments (pH <5).
Neutrophile: Prefers neutral pH (~7).
Alkaliphile: Thrives in basic environments (pH >9).
What are adaptations of extremophiles?
Psychrophiles: Have flexible proteins, unsaturated membrane lipids, and antifreeze proteins. Cannot survive in warmer climates due to protein denaturation. Found in polar regions and deep oceans.
Thermophiles & Hyper-thermophiles: Have heat-stable proteins and saturated membrane lipids. Found in hot springs and hydrothermal vents.
Barophiles: Adapted to high pressure with unique membrane compositions. Found in deep-sea trenches.
Halophiles: Maintain internal osmotic balance using compatible solutes. Found in salt flats and the Dead Sea.
Acidophiles: Maintain a neutral internal pH using proton pumps. Found in acid mine drainage and volcanic areas.
Alkaliphiles: Use Na⁺ gradients instead of H⁺ to maintain pH balance. Found in soda lakes and alkaline soils.
What is the advantage of growing in extreme environments?
Less competition from other organisms,
specialized enzyme adaptations for industry,
potential for survival in extraterrestrial conditions.
What is the heat-shock response?
What does it entail?
Which organisms use it?
A stress response triggered by sudden heat exposure.
It involves the production of heat-shock proteins (HSPs) that protect and refold denatured proteins.
Used by all domains of life.
What is water activity? How is it related to osmolarity? Which group of organisms have adapted to low water availability? What is the normal value of water activity to support growth?
Water activity measures available water (scale of 0 to 1). High osmolarity (solute concentration) lowers activity. Halophiles thrive in low aw. Most microbes require aw > 0.91.
How do organisms deal with osmotic stress?
They accumulate or expel compatible solutes (e.g., proline, K⁺) to balance internal and external osmolarity.
How do extreme halophilic Archaea and halophilic bacteria differ in their adaptation to high-salt conditions?
Halophilic Archaea use potassium (K⁺) to balance osmotic pressure, while halophilic bacteria produce compatible solutes like glycine betaine.
Why is a high pH or low pH in the cytoplasm problematic?
It disrupts enzyme function, denatures proteins, and affects membrane stability.
Does the optimal pH for proteins match the external pH of acidophiles and alkaliphiles?
No. Acidophiles maintain an internal pH higher than their environment, while alkaliphiles keep an internal pH lower than their environment.
What are some membrane transport mechanisms for dealing with differing pH conditions?
Proton pumps, antiporters, and symporters regulate internal pH.
What is aerobic respiration?
A process in which oxygen is used as the final electron acceptor in the electron transport chain to generate ATP.
Define the following: Strict anaerobe, Microaerophile, Facultative anaerobe, Aerotolerant anaerobe, Strict aerobe.
Strict anaerobe: Cannot tolerate oxygen; it is toxic.
Microaerophile: Requires low oxygen levels (<21%).
Facultative anaerobe: Can grow with or without oxygen.
Aerotolerant anaerobe: Does not use oxygen but tolerates it.
Strict aerobe: Requires oxygen for growth.
Why are some organisms sensitive to oxygen?
Oxygen generates toxic reactive oxygen species (ROS), which some organisms lack enzymes to neutralize.
Test tube oxygen gradient: Where do strict aerobes, microaerophiles, facultative anaerobes, aerotolerant anaerobes, and strict anaerobes grow?
Strict aerobes: Top.
Microaerophiles: Near top.
Facultative anaerobes: Throughout, but mostly at top.
Aerotolerant anaerobes: Evenly throughout.
Strict anaerobes: Bottom.
What is the function of superoxide dismutase, catalase, and peroxidase?
They detoxify ROS (e.g., superoxide radicals, hydrogen peroxide).
How are anaerobes grown in a lab?
Using anaerobic jars, gas-pak systems, or anaerobic chambers.
What is an oligotroph?
An organism that thrives in low-nutrient environments.
What maintains microbial diversity?
How does eutrophication affect microbial diversity?
Diversity is maintained through competition and niche differentiation.
Eutrophication (nutrient influx) disrupts balance, favoring fast-growing species and reducing biodiversity.
