extreme

Question 1

halorhodopsin

Answer 1

Halorhodopsin is a light-gated ion pump, specific for chloride ions, found in archaea, known as halobacteria.

Question 2

Halobacterium

Answer 2

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.

Question 3

“Salt-in” Strategy

Answer 3

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.

Question 4

Advantages and disadvantages of salt in strategy

Answer 4

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

Question 5

Applications of Halophiles

Answer 5

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.

Question 6

At what rate does Pressure increase by?
Can Barophillic organisms toletrate low pressures?
What is the rate of biochemical reaction increase relative to pressure

Answer 6

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

Question 7

Barophiles

Answer 7

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

Question 8

Phenotypic features of ubiquitous thermo-acidophilic bacteria from deep-sea hydrothermal vents

Answer 8

Main phenotypic features:
Motile (flagella)
Anaerobic (Fe and S as donor acceptors)
Extreme pH

Question 9

Life in Hadal trenches- deepest places in earth, key adaptations

Answer 9

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.

Question 10

What fraction of deep-sea animals are bioluminescent?

Answer 10

3/4

Question 11

Siphonophores

Answer 11

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

Question 12

Applications of bioluminescence

Answer 12

Self-sustainable lightning system in bacteria
Medical applications- in vivo imaging and diagnostics
Food industry (microbial contamination)

Question 13

Extreme Salinity

Answer 13

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

Question 14

Acidophiles -

Answer 14

Acidic

Again some thermal vents & hot spring

Question 15

Alkaliphiles

Answer 15

Alkaline

Soda lakes in Africa and Western U.S.

Question 16

Halophiles

Answer 16

• Highly saline
  Natural salt lakes and manmade pools
  Sometimes occurs with extreme alkalinity

Question 17

How cells adapt to survive in chemical extremes

Answer 17

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

Question 18

AlkaliphilesAlkali fly from Mono Lake

Answer 18

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

Question 19

AlkaliphilesBrine Shrimp –Artemia salina-

Answer 19

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.

Question 20

What is a Halophile?

Answer 20

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

Question 21

How halophiles survive?

Answer 21

Halophiles maintain an internal osmotic potential that equals their external environment.

Question 22

Halophiles structural modification (high salinity)

Answer 22

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.

Question 23

“Compatible Solute” Strategy

Answer 23

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.

Question 24

Compatible solutes

Answer 24

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

Question 25

Types of compatible solutes

Answer 25

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

Question 26

Types of extreme radiation

Answer 26

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

Question 27

Bdelloid rotifers

Answer 27

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

Question 28

Horizontal gene transfer

Answer 28

HGT is unique in rotifers. HGT is facilitated by membrane disruption and DNA fragmentation and repair associated with the repeated desiccation and recovery

Question 29

Deinococcus radiodurans

Answer 29

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