L17: Extremophiles Halophiles Flashcards
What are habitats of extremophiles
- temps
- pressure
- radiation
- salinity
- pH
- desscication
List the names of common extremophiles
hyperthermophiles, psychrophiles, acidophiles, alkaliphiles, halophiles, xerophiles, piezophiles
What is polyextremophile
organism that inhabits enviroment with multiple extreme conditions
Why study extremophiles
a. Evolutionary perspective – these types of organisms may have been the first life
forms on Earth!
b. Biotechnology potential of extremophile enzymes and biomolecules
c. Implications for Astrobiology, Exobiology, life on other planets, moons. Some extremophile microbiology is funded by NASA, CSA, and other Space Science agencies!
d. All extremophiles must contain adaptations / mechanisms to survive, grow and
reproduce in their respective environments.
What are the categories of halophiles
- Extreme halophiles
- Require high salt concentrations for growth and survival: 15 to 35% salt
- Mostly Archaea (Halobacteria, Halococcus, Natranobacterium), a few bacteria
(Ectothiorhodospira, anoxyphototroph), the green alga Dunaliella) - Moderate halophiles
- Grow with ~3 to 15% salt
- Wide variety from all domains, “true marine bacteria” require 3% NaCl - Slightly halophilic or halotolerant organisms
- All domains
- Tolerate high salt concentrations, do not require high salt concentrations
ex. Staphilococcus aureus
Where do halophiles live
Relatively widespread. They are found in salt marshes, subterranean salt deposits, dry soils,
salted meats, hypersaline seas, and salt evaporation pools.
§ Unique environments include surface of leaves of desert plants, nasal cavities of iguanas!
§ The Red Sea à named after Halobacterium that turns the water red during massive
blooms. The term “red herring” comes from the foul smell of salted meats that were spoiled
by Halobacterium. There have been considerable problems with halophiles colonizing
leather during the salt curing proce
Explore saltern in Utah US
Red pigment bacterioruberin protects haloarchaea cells from damage by light
WHAT IS Haloaquadratum walsbyi
– flattened morphology give greater surface-to-volume area
which may be useful in oligotrophic environments … ?
Describe osmotic effect / water activtiy with halophiles
aw: ratio of the vapor pressure of the air in equilibrium with a substance or solution to the vapor pressure of pure water
Halophile have evolved to grow best at reduced water potential
Extreme halophiles require high levels of salts for growth
Halotolerant organisms can tolerate some reduction in the aw of their environment. Grow best in the absence of the added solute
Describe conditions halophiles would have to make
Hypersaline environments are very stressful, denature proteins
Life at high salt concentrations is also energetically expensive
Halophilic microorganisms must exclude relatively high and toxic Na+ ion concentrations from cell interior but maintain osmotic balance.
What is the salt in the strategy
*Extreme halophiles maintain high internal concentrations of potassium and thus osmotic potential that equals their external environment.
* This “salt-in strategy” is primarily used by aerobic, extremely halophilic archaea and anaerobic bacteria
to maintain …
accumulating high concentrations of potassium chloride (KCl).
- Potassium (K+) ions enter the cell passively or actively via a uniport system.
- Sodium (Na+) ions are pumped out.
- Chloride (Cl-) enters the cell against the membrane potential via co-transport
with sodium ions.
- For every 3 molecules of KCL accumulated, 2 ATP are hydrolyzed
à Making this strategy more energy efficient than the “compatible solute” strategy
What is the compatible solute strategy
Cells maintain low concentrations of salt in their cytoplasm by balancing osmotic
potential with organic, compatible solutes.
- They do this by the synthesis or uptake of compatible solutes.
- Compatible solutes include polyols such as glycerol, sugars and their derivatives,
amino acids and their derivatives, and quaternary amines such as glycine betaine.
- Compatible solute can act as osmoprotectant
- Energetically this is an expensive process.
- Ex. Autotrophs use between 30 to 90 molecules of ATP to synthesize 1 molecule
of the compatible solutes.
- Ex. Heterotrophs use between 23 to 79 ATP
Name other halophile adaptations
Halorhodopsin: light driven membrane pumps that pump chloride into cell instead of pumping protons out => saves metabolic energy
Red and Organge Pigments called cartonoids: give red membrane colour
Cyoplasmic membrane has ATPase and ETC
Functional during normal aerobic heterotophic growth of organisms
Name an example of organisms and their adaptations
Dunaliella produce B-Carotene, shields cell from high light
intensities, protects from light damage.
What is the bacteriorhodopsin proton pump
- During periods of low oxygen concentration, some halophiles will synthesize bacteriorhodopsin
- Which is purple in color, and therefore is the origin of the the “purple membrane” found in haloarchaea!
- When bombarded by light photons, it becomes energized and “flips” protons from inside the cell to the outside, producing a PMF (proton motive force).
Discuss halophile cell envelope adaptations
Some halophiles, contain bacterioruberin, ~40 C in length,
stretch across entire membrane
- These altered lipids increase membrane stability in highly ionic
environment. - Cell envelopes DO NOT contain peptidoglycan, but rather layers of glycoprotein, which is highly negatively charged and dependent on Na+ ions for stability.
- Thus, they tend to have negatively charged proteins on the outside of their cell walls that stabilize it by binding to positively charged sodium ions in their external environments.
- If salt concentrations decline their cell walls may become unstable and
break down.
List applications of halophiles
- Carotenoids extracted from carotenoid-rich halobacteria and halophilic algae are used
as food additives / food-coloring agents / health additives à anti-oxidative activities
§ Halophilic organisms are used in the fermentation of soy sauce and Thai fish sauce.
§ Antimicrobials à Halocin for leather processing
§ Unique compatible solutes (ectoines), used as stabilizing solutes for vaccines, halophile derived salt crystals are potential vaccine delivery
§ Enzymes that function in low-water conditions?
§ Increasing crude oil extraction?
§ Genetically engineering halophilic enzymes encoding DNA into crops to allow for salt tolerance? Treatment of waste-water?
§ Bacteriorhodopsins à electronic circuits and memory devices?
