Xerophiles (Extreme environment I) Flashcards
Examples of general extreme environments?
Yellowstone (ph), sea vents (hot), frozen lake (cold), desert (no water)
What are different extremophiles (16)?
- Acidophile - optimal growth at pH levels of 3 or below
- Alkaliphile - optimal growth at pH levels of 9 or above
- Endolith - lives in microscopic spaces within rocks (pores between peds)
- Halophile - requires at least 0.2M concentrations of salt for growth
- Hyperthermophile - can thrive at temperatures between 80–122 °C
- Hypolith - lives inside rocks in cold deserts
- Lithoautotroph - source of carbon is CO2 and exergonic inorganic oxidation
- Oligotroph - capable of growth in nutritionally limited environments
- Osmophile - capable of growth in environments with a high sugar concentration
- Piezophile - lives optimally at high hydrostatic pressure
- Polyextremophile - qualifies as an extremophile under more than one category
- Psychrophile/Cryophile – temperature optima of 15 °C or lower
- Radioresistant - high levels of ionizing radiation (UV), also including organisms capable of resisting nuclear radiation
- Thermophile - can thrive at temperatures btwn 60–80 °C
- Thermoacidophile - combination of thermophile and acidophile
- Xerophile - can grow in extremely dry, desiccating conditions
Whats an xerophile?
tolerates very dry conditions
• endoliths (rock) and halophiles (salt) are usually xerophilic
Whats aw? What do bacteria and fungi need?
- aw= water activity= is the amount of H2O in a substrate that an organism can use to support growth
- bacteria usually req aw~0.91, fungi need ~0.7
Look at slide 23, lecture 4
Good
What are some adaptions to the challenges of low H2O ?
• ability to protect and repair DNA exposed to UV
• maintain protein stability in dehydrated state
• maintain membrane integrity
•Primary mechanism is production of extracellular polysaccharide (EPS) and water stress proteins
- EPS regulates uptake and loss of H2O
- may protect cell walls from shrinking
- EPS may include UV absorbing cmpds
Where is the driest place on earth?
- Atacama desert
- H2O availability, temperature and UV radiation are stressors
- less than 1 mm of rain / year
- sparse or absent plant life – therefore no organic material in soil (0.02-0.09% TOC)
What are hypoliths and endoliths?
hypoliths (rock surfaces) endoliths (pore spaces in rocks)
How do rocks help bacteria/
Protect against UV and can trap small H2O amounts
What is Dunaliella algae?
- Discovered in 2010 in a cave in Chile’s Atacama desert
- Can thrive on very little water. -Grow on top of spiderwebs to capitalize on dew – the meager amounts of air moisture that condense on the webs in the mornings.
How was the Atacama Desert examined? What did they find?
-Soil bacterial diversity was examined along a W to E elevation transect
(400 – 4500 m)
-H2O was the limiting factor
- rocks were collected in four locations along an aridity
gradient (21 mm to <2mm /yr)
- % of rocks colonized by cyanobacteria declined from 28 to <0.1%
Acidithiobacillus ferrooxidans
Lives in pyrite, metabolizes iron and sulphur
Acidithiobacillus thiooxidans
- lives in soil and corroding concrete sewer pipes, consumes sulphur
- produces sulphuric acid
Whats desert varnish? What lives on them? Protection? How is it formed?
- shiny, dense and black varnishes on basalt, fine quartzite and metamorphosed shales
- thin coating (patina) of manganese, iron and clays
- include colonies of bacteria and lichens (more microbes)
- includes cemented clay particles which help to shield the bacteria against desiccation, extreme heat and intense solar radiation
- bacteria absorb trace amounts of Mn and Fe from the atmosphere and precipitate it as a black layer of manganese oxide or reddish iron oxide on the rock surfaces
What are Metallogenium and Pedomicrobium?
-spherical, rod-shaped or pear-shaped cells 0.4 to 2 um long,
with peculiar cellular extensions
- appendaged bacteria or budding bacteria
-Mn+2 +H2O MnO2 +4H+ +2e-
- Fe+2 + 3H2O Fe(OH)3 +3H+ + e-
