Halophiles, alkaliphiles (Extreme environments III)

Question 1

Halophilic, alkaliphilic orgs? what do they inhabit?

Answer 1

-Love high salt, high pH
-inhabit hypersaline environments with salt concentrations
up to saturation
- archaea, bacteria, and some eukaryotes
- categorized slight, moderate or extreme

Question 2

High salt env?

Answer 2

• The vivid red brine (teaming with halophilic archaebacteria) of Owens Lake, CA
• Red brine from Searles Lake, a salt lake in the arid Mojave Desert of California

Question 3

What causes water to move into the cell?

Answer 3

Cytoplasm has a higher solute concentration than the surrounding environment

Question 4

What happens when cell is in an environment with a higher external solute concentration

Answer 4

Water will flow out unless the cell has a mechanism to prevent this

Question 5

Halophile salt tolerance.

Answer 5

• the extreme halophiles or haloarchaea or halobacteria require at least a 2 M salt concentration (about 36% w/v salts)
• some require salt for growth and will lyse in anything other than a very high concentration salt-conditioned environment

Question 6

Whats the halophiles number one challenge?

Answer 6

• Need to avoid protein aggregation
• most proteins are less soluble in solutions of high salt concentrations
• causes a precipitation of proteins which differs from protein to protein

Question 7

Whats salting out? Result?

Answer 7

Salting out is:
• at higher conc’s all the binding sites on protein become occupied with salt ions
• salt ions then interact with solvent
• decreases the number of water molecules available to
interact with the charged part of the protein
• Result of the increased demand for solvent molecules, the protein-protein interactions are stronger than the solvent-solute interactions; the protein molecules precipitate
• Solubility of the protein decreases

Question 8

Whats salting in?

Answer 8

Salting in is:
• Small amount of salt, the solubility of the protein increases slightly b/c ions from the salt associate with the surface of the protein
• this shields those areas from the water and less water molecules are required to interact with the protein surface to keep it in solution
• the “activity” of the water has increased and the protein becomes more soluble therefore preventing aggregation and precipitation

Question 9

Why does salting out happen?

Answer 9

• water moves out of cell in response to high salt gradient
• costs energy to avoid desiccation
• two strategies:
- both increase the internal osmolarity of the cell
-osmolarity = the number of osmoles (Osm) of solute
per liter (L) of solution (osmol/L or Osm/L)
- can also use a measure of the osmoles of solute per kilogram of solvent (osmol/kg or Osm/kg)

Question 10

Ecotine

Answer 10

-confers resistance towards salt
and T stress
• stabilizes proteins and other cellular stuctures

Question 11

Trehalose

Answer 11

-sugar forms gel

• high water retention capabilities • prevents disruption of organelles

Question 12

osmoprotectants

Answer 12

• Neutral
• help with osmotic stress
• can also help in dry environments

Question 13

More radical adaptation involves balancing external high salt conc by…

Answer 13

…accumulating inorganic ions to conc that exceed medium

• selective influx of K+ and Cl- ions into the cytoplasm
• involves the entire intracellular machinery (enzymes, structural proteins, etc.) b/c all cellular components must adapt to function in high salt

Question 14

How do enzymes and other proteins require high salt for activity and structural stability?

Answer 14

Cellular machinery is adapted to high salt concentrations by having charged amino acids (-’ve) on their surfaces, allowing the retention of H2O molecules around them

Question 15

The dead sea

Answer 15

• surface and shores are 422 m
below sea level 
• 378 m deep
• one of the saltiest – 33.7% salinity
• 67 km long, 19 km wide, main tributary is the Jordan River
• no outlet
• Ca, K, and Mg salts

Question 16

Problems in dead sea?

Answer 16

• environmental conditions are changing with time
• water diversions a huge problem
• also a high light environment
• during floods, the salt content can drop to 30% or lower

Question 17

Why did dead sea turn red in 1980?

Answer 17

• algae bloom – Dunaliella salina
• Dunaliella does not need high salt to function
• it does have a salt-tolerant enzyme, carbonic anhydrase, which is uniformly negative
• gylcerol is also used as an osmoprotectant

Question 18

Spain solar salterns

Answer 18

• evaporate sea water leading to precipitation of CaCO3 and
CaSO4 and a hypersaline NaCl brine that precipitates
• bacteria grows on resulting crystallizers
• dominated by archaea
but also 5 to 30% halophilic bacteria

Question 19

Salinibacter ruber

Answer 19

• bacteria can comprise up to 25% of the prokaryotic community, but is more commonly a much lower percentage of the overall population
• brightly red-pigmented, motile, rod-shaped, grew optimally at salt concentrations between 20 and 30% and did not grow below 15% salts

Question 20

Example of bacillus surviving in salt crust.

Answer 20

bacterial Bacillus spores have been isolated from pockets in salt crystals harvested from an underground salt deposits formed from an ancient sea ~ 250 mya

Question 21

Chaplin Lake

Answer 21

• 52 km2 - the 2nd largest saline water body in Canada
• up to 184 ppt of salt
• lots of birds, sodium sulphate
harvest
• shore flies, brine shrimp, midge larval, and seeds provide food
• few predators

Question 22

Alkaliphilic; includes? challenges?extreme pH?

Answer 22

-thrive in pH ~9-11
• include prokaryotes, eukaryotes, and archaea
• high alkalinity challenges – H+ are scarce, must maintain internal pH ~8 by making cytoplasm more acidic
• African rift lakes or soda lakes
• extremely alkalophilic bacteria that grow optimally at pH 10.5 and above are generally aerobic bacilli that grow at mesophilic temperatures and moderate salt levels

Question 23

pH homeostasis can be achieved via both active and passive regulation mechanisms explain passive.

Answer 23

passive:
• cytoplasmic pools of polyamines - rich in aa’s with
+’ve charged side groups (lysine, arginine, and histidine) • low membrane permeability
• pH stable enzymes - both excreted and surface located must be resistant to the effects of extreme pH
• -’ve charged polymers within their cell membranes, which help combat the high conc of OH-

Question 24

pH homeostasis can be achieved via both active and passive regulation mechanisms explain active

Answer 24

active:
• constantly pumping H+ in the form of H3O+ across their
cell membranes into their cytoplasm
• the pH gradient must be reversed to carry out ATP synthesis
• Na+ ion channels largely convert the H+ gradient into
an electrochemical Na+ gradient

Question 25

What do biological detergents contain? What can they do? Used as what? Example?

Answer 25

-Alkaline enzymes produced
from alkaliphiles
• proteases hydrolyze peptide bonds
• extracellular
• can digest insoluble polymers such as cellulose, protein, and starch
• products of digestion are then transported into the cell where they are used as nutrients for growth
• soaps are alkaline

Question 26

How are cyclodextrin sugar molecules produced? How does it enhance solubility and bioavailability?

Answer 26

• are produced using an enzymatic conversion that
originated from alkaliphilic orgs
• because cyclodextrins are hydrophobic inside and hydrophilic outside, they can form complexes with hydrophobic compounds, thus enhancing the solubility and bioavailability of such compounds

Question 27

Lake Natron – Africa’s Great Rift Valley – “soda lake”

What river feds into it? Depth? Temp? colours from what?

Answer 27

• pH 9-10.5, depending on rainfall
• caustic
• fed by the Ewaso Ng’iro river
and mineral-rich hot springs 
• less than 3 m deep
• width varies with water level
 • temps can reach 50 °C
red, pink, and orange colours are carotenoids from Spirulina
• in soda lakes, Spirulina out competes other algae

Question 28

What do flamingos feed on? how?

Answer 28

evolved a filter feeding beak that allows them to feed exclusively on these cyanobacteria

Question 29

Mono Lake CA
How old?
Evaporation leads to what?
What are tufa formations?
pH?

Answer 29

-760000 yo terminal lake
• evaporation leads to increased salts leads to increased alkalinity and pH
• also fed by As rich groundwater
• tufa formations – underwater springs bubble up, Ca in spring water reacts with carbonate in lake to form structures
• LA wanted the H2O, so diverted lake in 1940s
• pH 10, 75-90 g salts /L
• brine shrimp (Artemia)

Question 30

In 2008 found unique PS As oxidizer in pools on the side of Mono Lake CA.
What did it oxidize? Draw backs?

Answer 30

• arsenite (As III as AsO3-3) to arsenate (As V as AsO4-3)
• As III is poisonous due to P mimicry
• Ectothiorhodospira-like purple sulphur bacteria
• anaerobic

Question 31

What gives clues to early metabolism?

Answer 31

Primordial PS

Question 32

How does protein folding help dissolve proteins in water? Proteins in pure water?

Answer 32

-proteins will fold such that hydrophobic amino acids will form protected hydrophobic areas
• hydrophilic amino acids interact with water and allow proteins to form hydrogen bonds with the surrounding water molecules
• if the protein surface is hydrophilic, the protein can be dissolved in water
• Usually: Proteins in pure water are not very soluble – usually aggregate and precipitate- can’t fold