extreme Flashcards
halorhodopsin
Halorhodopsin is a light-gated ion pump, specific for chloride ions, found in archaea, known as halobacteria.
Halobacterium
Halobacterium species are members of archaea.
Widely researched for their extreme halophilism and unique structure.
Require salt concentrations between 15% to saturation to live.
Use the “salt-in” strategy.
“Salt-in” Strategy
Cells can have internal concentrations that are osmotically equivalent to their external environment.
They maintain osmotically equivalent internal concentrations by accumulating high concentrations of potassium chloride.
To use this strategy all enzymes and structural cell components must be adapted to high salt concentrations to ensure proper cell function.
Advantages and disadvantages of salt in strategy
Advantages:
Energetically less costly than synthesizing organic solutes
Disadvantages:
Requires extensive internal adaptations -enzymatic machinery and metabolism
Limited habitat range – proteins degrade in low salt conditions
Applications of Halophiles
The extraction of carotene from carotene rich halobacteria and halophilic algae that can then be used as food additives or as food-coloring agents.
The use of halophilic organisms is widely used in the fermentation of soy sauce, Thai fish sauce and other food products.
At what rate does Pressure increase by?
Can Barophillic organisms toletrate low pressures?
What is the rate of biochemical reaction increase relative to pressure
Pressure increases by 1 atmosphere / 10 m
Barophilic organisms adapted to high pressures, and cannot tolerate low pressure
Biochemical reaction rates increase with pressure up to ~100 atm, but decrease beyond that
Barophiles
Survive under levels of pressure that are otherwise lethal to other organisms
- Usually found deep in the earth, in the deep sea, hydrothermal vents, etc
- Barophilic microorganisms could potentially survive on other planets
Phenotypic features of ubiquitous thermo-acidophilic bacteria from deep-sea hydrothermal vents
Main phenotypic features:
Motile (flagella)
Anaerobic (Fe and S as donor acceptors)
Extreme pH
Life in Hadal trenches- deepest places in earth, key adaptations
Key adaptations :
Use of intracellular protein-stabilising osmolytes (trimethylamine N-oxide), which act to maintain enzyme function by increasing cell volume.
Increased use of unsaturated fatty acids in cell membrane phospholipids to maintain their fluidity.
What fraction of deep-sea animals are bioluminescent?
3/4
Siphonophores
The zooids in a siphonophore colony are descended from a single fertilized egg (unique example of cloning in animals).
The egg develops into the protozooid, a polyp that gives rise through budding to all the other zooids of the colony.
The very early development of cystonects is completely unknown.
They capture prey with specialized stinging capsules called nematocysts
Applications of bioluminescence
Self-sustainable lightning system in bacteria
Medical applications- in vivo imaging and diagnostics
Food industry (microbial contamination)
Extreme Salinity
Salts are present in 36 ppm in seawater
Nitrogen and phosphorus are minor elements but are present in sufficient quantity for metabolism
pH varies between 6.5 and 8.3, average ~7.0
Only CO3- and HCO3- availability are affected by pH
Acidophiles -
Acidic
Again some thermal vents & hot spring
Alkaliphiles
Alkaline
Soda lakes in Africa and Western U.S.
Halophiles
- Highly saline
Natural salt lakes and manmade pools
Sometimes occurs with extreme alkalinity
How cells adapt to survive in chemical extremes
Interior of cell is “normal”
Exterior protects the cell
Acidophiles and Alkaliphiles sometimes excrete protective substances and enzymes
Acidophiles often lack cell wall
Enzymes from these organisms are of biotechnological and industrial interest
AlkaliphilesAlkali fly from Mono Lake
Colonizes extreme alkaline environments
Adult life span 3-5 days
Eggs laid on surface of water which hatch on algae at the bottom of the lake
Pupae floats and is taken to shore by wind
AlkaliphilesBrine Shrimp –Artemia salina-
Colonizes inland saltwater lakes but not oceans
Eggs protected as cysts
Cyst tolerate extreme chemical conditions and desiccation
Eggs hatch in salted water
Used commercially as novelty gift “Sea Monkeys” and tropical fish food.
What is a Halophile?
Divided into mild (1-6%NaCl), moderate (6-15%NaCl), and extreme (15-30%NaCl)
Halophiles are mostly obligate aerobic archaea
How do halophiles survive high salt concentrations?
Proteins interact more strongly with water
by increasing the abundance of small molecules inside the cell, and these, then, compete for the water
and by accumulating high levels of salt in the cell in order to compensate the salt outside
How halophiles survive?
Halophiles maintain an internal osmotic potential that equals their external environment.
Halophiles structural modification (high salinity)
Structural modification of external cell walls- posses negatively charged proteins on the outside which bind to positively charged sodium ions in their external environments & stabilizes the cell wall breakdown.
“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- glycerol, sugars and their derivatives, amino acids and their derivatives & quaternary amines such as glycine betaine.
Energetically synthesizing solutes is an expensive process.
Compatible solutes
Small, organic, water soluble molecules that are accumulated to molar concentrations and do not interfere with cell metabolism.
Excludes salt from the cytoplasm
Accumulated compatible solutes used to balance osmotic potential
Are either synthesised internally or taken up from the surrounding environment
Types of compatible solutes
Commonly amino acids or their derivatives, sugars, polyols, betaines, ectoine and sugar derivatives
Usually neutral
Polyols: Found in halophilic Eukaryotes - eg Glycerol in halotolerant yeast Debaryomyces hansenii
Betaine: Found in halophilic bacteria and methanogens - eg in Halomonas elongata and Methanohalophilus portucalensis
Ectoine: Synthesised by a wide range of bacteria and is major solute isolated from bacteria living in saline Mono Lake, CA
Types of extreme radiation
Non-ionizing radiation = excites molecules UV radiation (sunlight), Radiowaves, Microwaves
Ionizing radiation (IR) = ionizes molecules
X- and γ – rays
Ionizes molecules by colliding with electrons
Free radicals produced
Bdelloid rotifers
survive desiccation, highly resistant to UV and ionizing radiation. They survive not by protecting their DNA from UV damage but by protecting their DNA repair machinery!!
Massive horizontal gene transfer (HGT) in rotifers
Horizontal gene transfer
HGT is unique in rotifers. HGT is facilitated by membrane disruption and DNA fragmentation and repair associated with the repeated desiccation and recovery
Deinococcus radiodurans
Possesses extreme resistance to up to 4 million rad of radiation, genotoxic chemicals (those that harm DNA), oxidative damage from peroxides/superoxides, high levels of ionizing and ultraviolet radiation, and dehydration
-It has from four to ten DNA molecules compared to only one for most other bacteria
