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Lecture 4

Lecture 4 Life in Extreme Environments.docx
Lecture 4 Life in Extreme Environments.docx

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McMaster University
Life Sciences
Luc Bernier

Life in Extreme Environments: What are the Conditions Needed for Life?:  Temperature: 0-50 degrees Celsius  pH: 4-8 o Extreme boundaries  Pressure: 101.3 kPa  Oxygen  Water  Carbon dioxide Range of Tolerance:  Most organisms have a well range of tolerance  When we move away from the optimum range (for any parameters listed above), we see less and less of these organisms o They will still be able to live, but it will be much harder for them to be viable o Beyond these limits of tolerance, it is lethal o Temperatures are too cold or too hot, there will be no fish  Doesn't take into account the extent of biodiversity Phylogenetic Tree of Life:  In terms of morphology, they almost look identical  Some of these microorganisms, some of them are in fact far more different genetically than with fungi and animals o Genetically we are closer to plants and fungi then other organisms that look virtually identical Australian Desert:  12 month droughts  Diversity tends to be found in the two kingdoms (Achaea and Eucharya) Atacama Desert, Chile:  >1mm rain/year  Extremely dry Antarctic Ocean:  Water temperature: -2 degrees Celsius  Staying liquid because of the salt content  Organisms are able to adapt What Exactly is an Extreme Environment?:  Very trivial, because it is based on humans  What is extreme for us is perfectly normal for other organisms  Liquid water is an absolute requirement of life on Earth  Life requires energy o This is going to be done through a flow of electrons based on redox chemistry  Redox chemistry used to control energy flow o The difference in energy potential will vary o We are up in the ladder because water generates the most amount of energy o Organic chemistry must operate - we need to apply it in life to exist What is an Extremophile?:  An organism that thrives in an extreme environment  Physical extremes: o Temperature o Radiation o Pressure o Extreme dryness  Geochemical extremes: o Salinity o pH o Oxygen species o Redox potential that they can exploit for the transfer of energy  Very rare that extremophile will adapt to only one extreme o In a desert, there will be a temperature extreme, a salinity extreme o Polyextremophiles are organisms that can adapt to more than one extreme Types of Extremophiles:  If you look at the pH scale there are organisms that can survive in any pH  Acidophile: an organism that grows best at acidic (low) pH values (below 4)  Alkaliphile: an organism that grows best at high pH values  Anaerobe: thrive under conditions where there is virtually no oxygen o Sometimes exposure to oxygen is lethal  Halophile: they require high concentrations of salt to grow  Endolith: they are living inside rocks, and minerals o Before this, we didn't know that we could find organisms in rocks Types of Extremophiles:  Methanogen: an organism that produces methane o From the reaction of hydrogen and carbon dioxide o Really under conditions where there is no oxygen present o Most redox conditions that involve nitrogen and sulphur are absent o Primarily members of the Achaea kingdom  Barophile: live in high pressure o Over 700 atmosphere (700 times the normal atmosphere - extremely high pressure) o The deep ocean  Psychrophile: thrive under very cold conditions o Optimal growth is 15 degrees Celsius or lower  (Hyper) Thermophile: temperature is 50 degrees Celsius or above o Hyper is 80 degrees Celsius and above  Xerophile: adapte
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