Lecture 1: Hypersaline

Question 1

why study extreme environments?

Answer 1

• origin of life on earth
• life on other planets
• extreme environments are common
• diverse communities
• polluted environments are extreme
• source of robust enzymes

Question 2

What is an extreme environment?

Answer 2

• difficult to explain

- conditions extreme for one (prevent growth & may lead to death) organism are essential for another to grow

Question 3

ultra-extreme environments

Answer 3

• they prevent the growth of, and may be lethal, to most organisms
• dominated by ‘extremeophiles’
• often v stable - obligate extremeophiles dominate

Question 4

Hyper-saline environments: natural & artificial

Answer 4

Natural = Great salt lake, dead sea, kenyan soda lakes

Artificial = salterns (sea water left to evaporate to salt)

Semi-natural = Mono Lake, Owens valley, irrigated areas

Question 5

hypersaline environments arise where ___ are high, ___ is low

Answer 5

evaporation rates high, rainfall low

- lots of rainfall on one side of mountain, prevailing winds, rives run down and other side = hypersaline

Question 6

hyper-saline environments are found

Answer 6

deep sea vents, mud volcanoes, cold seeps, beneath ice sheets, within ice crystals
- wherever you have water flowing over geology (rocks) and there is a reason for conc effects (i.e. evaporation / high temp)

Question 7

wherever ice forms you get

Answer 7

a hyper-saline environment

water freezes, solutes are excluded

Question 8

characteristics of hyper-saline environments

Answer 8

• 10x saltier than sea water
• Great salt lake rich in Na+ and Cl-
  BUT dead sea is Na+, Cl- with Mg2+ (other ions too)
• pH pretty neutral

Question 9

organisms in hyper-saline environments = obligate/facultative

Answer 9

Halotolerant = facultative up to 0.3M

Moderately halophilic = obligate in 0.2-2.0M

Extremely halophilic = obligate 3 - 5M

Question 10

Woese et al 1990 produced what

Answer 10

universal phylogenetic tree

• w 3 domains (bacteria, archaea, eucarya)
• probably wrong, as diversity in archaea is so great, we have just not explored it

Question 11

organisms found in hyper-saline environments?

Answer 11

• mixture (eukaryotes, bacteria & archaea)

Question 12

studying hyper-saline environment challenges and how we solve these

Answer 12

• in more remote areas of world (transport, long way from lab etc, might be in national park)
• Salterns are useful (sea water evaporated for salt production)
• • readily accessible & controllable
• • artificial BUT good approximations of natural systems
• -found in many arid regions

Question 13

Salterns: Commonly contain

Answer 13

Dunaliella salina (euk) & Halobacterium sp. (archaea)

Question 14

Dunaliella salina in salterns

Answer 14

• Eukaryote
• tolerate wide range of salt conc
• photosynthetic over much of the range
• produces chlorophyll until salt concentrations rise too high
• then produces carotene as a photoprotectant & glycerol (commercially useful products)

Question 15

Halobacterium in salterns

Answer 15

• archaea

- photosynthetic but in diff way to Dunaliella salina

Question 16

problems with high salt concentrations for organisms

Answer 16

i.e halobacterium and Dunaliellla salina

OSMOTIC EFFECTS

• • water lost from the cell
• • dehydration

IONIC EFFECTS

• • ions (particularly Na+) disrupt ionic bonds
• • high salt can denature and precipitate proteins

Question 17

how does Dunaliella salina cope with a fluctuating salt environments?

Answer 17

• under low salt conditions it is photosynthetic (stores starch)
• as salt conc rise, water leaves the cell & photosynthesis is inhibited
• set of salt tolerant enzymes is activated which convert STARCH to GLYCEROL
• – osmolyte (causes water to re-enter the cell)
• – compatible solute – protects proteins
• – photosynthesis restored
• if salinity declines (i.e. after rain) glycerol is converted back to starch

Question 18

How does halobacterium cope with a fluctuating salt environments

Answer 18

• unusual lipids in the outer membrane makes them v robust
• proteins are highly salt tolerate (lots of acidic residues on their surface, interact w K+)
• obligate halophiles
• photosynthetic BUT utilise BACTERIORHODOPSIN

Question 19

what is found at the bottom of salterns?

Answer 19

Microbial mats

• • surface of the mat is dominated in cyanobacteria
• • high O2 due to photosynthesis

Question 20

what happens when all the water is gone? Bacteria & Archaea e.g.

Answer 20

cyanobacteria & Haloarucla

• – can survive in solid salt, yes, how long for? they cant grow, as no room to grow, but are they still doing something? suspended animation or metabolically active?
• – organisms can possibly survive for millions of years in solid salt utilising the carbon source deposited the same time as them