Psychrophiles (Extreme environments IV)

Question 1

What are psychrophiles?

Answer 1

Grow and reproduce at low T, inhabit permanently cold environments

Question 2

Whats psychrotolerant?

Answer 2

Grow at 0oC but have optima of 20oC to 40oC

Question 3

Is psychrotolerance or psychrophiles more common?

Answer 3

Psychrotolerant

Question 4

Examples of cold environments

Answer 4

• Alpine and arctic soils, high-latitude and deep ocean

waters, polar ice, glaciers, and snowfields

Question 5

What kind of microbes usually occupy cold environments?

Answer 5

Most are bacteria or archaea, some psychrophilic fungi and eukaryotic cold- adapted
organism

Question 6

What happens to membranes in lower temps?

Answer 6

• fluidity of membranes decreases with lower T

Question 7

Psychrophile adaptions?

Answer 7

1. membrane is more flexible due to higher ratio of
   unsaturated to saturated fatty acids
2. enzymes function at low T and are denatured at moderate T
3. proteins also need to be more flexible b/c low T reduces chemical rxn rates
   • might be the entire protein or just parts
4. also have cold shock proteins and cold acclimation proteins
5. need to protect against ice formation
   I. use “antifreeze” molecules / proteins
   II. bind to ice crystals by large complementary
   surfaces and lower the T at which an org can grow
   III. trehalose may have a colligative effect, but probably also helps in preventing protein denaturation and aggregation

Question 8

Why do psychrophile proteins need to be more flexible?

Answer 8

• Improved catalytic efficiency but not hugely different than mesophilic homologues
• Conformational flexibility is needed at the reaction site by reducing structural factors and reducing interactions
• Reduce of the number of ion pairs, H+ bonds and hydrophobic interactions among others
• More α-helices than β-sheets
• More polar and less hydrophobic amino acids
• Fewer weak bonds
• Decreased interactions between protein domains

Question 9

Whats the difference between cold shock proteins and cold acclimation proteins?

Answer 9

• cold-shock proteins have increased levels of nucleic- acid-binding proteins and chaperones
• cold-acclimation proteins are produced to cope with continuous cold temperatures

Question 10

Whats sea ice spaces filled with? 
What does it form?  
Where are microbes found? Chlorophyll content? 
What supports ice bacteria?
Who are the primary producers?

Answer 10

• filled with brine- forms a 3D network of tubes; rapid changes in light intensity T and salinity
• MOs found in brine sol’n on the underside of the ice; mostly diatoms
• chlorophyll content is 100X greater in this layer than in surrounding sea H2O
• DOM from the waste of algae supports ice bacteria, also find viruses, protozoans and fungi
• Unicellular algae

Question 11

Watermelon snow, snow algae. Why are they red? Example? Sun cups?

Answer 11

• depth of 25 cm
• teaspoon of melted snow may contain a million or more cells
• Ex: Chlamydomonas nivalis - green algae containing a secondary red carotenoid pigment (astaxanthin)
• astaxanthin protects chloroplast from intense visible and UV
• absorbs heat providing liquid H2O as the snow melts around it
• accumulate in “sun cups”,
  shallow depressions causes by the heat produced
  

Question 12

Greenland glacier ice cores- process and what was found?

Answer 12

-ice cores sample to 3200m depth
- initially taken as a climate proxy
- -9°C, extreme pressure, very little O2, oligotrophic
- Chryseobacterium greenlandensis – 1 of only ~10 microbe species that have been described
– 1 of only ~10 microbe species that have been described

Question 13

Chryseobacterium greenlandensis

Answer 13

• deposited in greenland glacier when glacier formed 120000 yo
• origins unknown
• v.v. small (10-100 X smaller than E. coli)
• large surface to volume ratio allows from more efficient uptake of nutrients
• ultrasmall size means they can exploit microenvironments and avoid predators

Question 14

McMurdo Dry Valleys in Antarctica

Answer 14

-series of valleys, lakes, and rivers in Victorialand
• driest and coldest place known
• mean annual surface air T -27.6°C (ours is 2.8°C), surface soil -26.1°C
• unusual solar cycle

Question 15

Permanently covered lakes in McMurdo Dry Valleys

Answer 15

-3-5 m of ice
• permanent ice = reduced wind driven mixing of water column
• reduced gas exchange
• reduced light penetration reduced sediment deposition
into water column
• long mixing times result in chemical gradients that may exist in H2O column for 20000 y
• pressure of the ice results in melting and formation of the lakes

Question 16

Lake Vostok – freshwater lake

Facts (area, depth, pressure, T, nuts, and how much under surf? Formation? Geothermal heat and ice sheet role?

Answer 16

-Facts
• largest of Antarctica’s ~400 known subglacial lakes
• 4000m under the surface of the central East Antarctic Ice Sheet sealed for millions of years
• area=15,690 km2
• depth 344 m
• oligotrophic, expected to be supersaturated with nitrogen and oxygen
• average water T ~−3 °C
• under 354.60 bar of pressure

-Formation
• lake water sealed off ~15 million years ago
• water of the lake is continually freezing and being carried
away by the motion of the Antarctic ice sheet
• at the same time, water is being replaced by melting from other parts of the ice sheet in high pressure conditions

• Geothermal heat from the Earth’s interior may warm the bottom of the lake
• ice sheet itself insulates the lake from cold temperatures on the surface

Question 17

Lake Vostok Russian scientists drilled into it in 2012

What did the core show?

Answer 17

• ice core provides a continuous paleoclimatic record of
400,000 years
• first core of freshly frozen lake ice obtained on 10 January 2013 at a depth of
3,406 m
- Sequenced microbes in the core