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BIOL0129_Lecture 10

BIOL0129_Lecture 10 - Before we consider what is extreme we...

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1 Introductory Microbiology Lecture 10 Microbes and the limits of life Before we consider what is ‘extreme’, we need to define what is ‘normal’ So for humans this means - An oxygen-rich atmosphere Average temperature of ~20 o C Pure liquid water Organic food source (and this is true for most life) Once we start to deviate from these conditions life gets stressful - Generally speaking, the more ‘extreme’ conditions get - the fewer animals and plants you encounter
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2 Hot deserts Polar regions Deep oceans OK, but what happens when conditions get REALLY extreme?
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3 A few simple animals such as tardigrades survive extreme desiccation, cold etc in a resting state Several plants and fungi also produce resting spores But this is not really ‘living’ ! • Imagine life that can actively grow and reproduce in: –rocks deep underground –places with almost no water –lakes 10 times more salty than seawater –boiling hot water springs –radioactive waste –Strong acid and alkali solutions • Only a very select group of organisms can do this –Collectively called ‘extremophiles’ –They are all microorganisms This is because they have relatively simple unicellular bodies, rapid evolutionary capability and a highly versatile metabolism
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4 Let us consider a few examples … Hyper-arid deserts The Taklimakan Desert in western China • Water is severely limited – <25mm/year mean annual rainfall – Decadal periods without rain – Can be very hot (Taklimakan) or very cold (Antarctic Dry Valleys) • Without water life is restricted – Complete absence of animal and plant life – Only detectable life is clinging to rocks under the soil surface
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