Limits of Life and Extremophiles Lecture 10 Post Midterm No copyright infringement is intended by the creation or use of these notes There are rules that define life o Water and temperature are the only known variables that prevent growth and survival of organisms Extremophile o An organism that thrives in extreme environments Meaning it doesn t only survive but it successfully lives and functions o Typically refers to prokaryotes and bacteria archaea o Most known extremophiles are microbes Types of Extremophiles classifications o Classified after the conditions they thrive in and can thrive in multiple o Temperature Adaptations 80 degrees Celsius Thermophile organism can thrive at temperatures between 60 Hyperthermophile organism can thrive at temperatures between 80 122 degrees Celsius Found in hydrothermal systems Psychrophile Cryophile organism can thrive at temperatures 15 degrees Celsius or lower Found in cold soils permafrost polar ice cold ocean water in under alpine snowpack Mesophiles organism thrives best a moderate temperatures 25 40 degrees Celsius Difficulties Organisms grow best at optimal temperature and growth rate decreases at too high or too low temperatures High Temperatures Thermo Hyperthermophile o Problem protein nuclei acid denaturation This means the loss of 3D structures for nucleic acid and loss of functions for some enzymes Loss of solubility a result of protein denaturation o Solution heat shock proteins help fix enzymes that have been denatured higher GC content in RNA sequence Guanine and Cytosine have a triple bond compared to Adenine and Uracil s double therefore they are harder to break and can stand higher temperatures Low Temperatures Psychrophile Cryophile o Problem o Solution Cell freezing and membrane stiffness Anti freeze proteins these proteins can help protect cell structures from extracellular water freezing and thawing They can also help lower the freezing temperature of water Membrane Fluidity The membrane stiffens when its colder and so fluidity is decreased To counter this psychrophiles cryophiles increase ratio of unsaturated to saturated fatty acids thus retaining the required flexibility of membrane o pH Adaptations pH scale balances out H with OH but since H is a much greater than OH in the balance for water we use pH log H Acidophile organism thrives at pH 3 or below Alkaliphile organism thrives at pH 9 or above Difficulties High H Low pH Acidophile o Problem o Solution High acidity causes protein or other molecule denaturation Passive and active transport of H Acid resistant proteins help protect cell from acidic solutions Low H High pH Alkaliphile o Problem o Solution High alkaline nature causes protein or other molecules to denature Amino acids with positively H side groups to buffer cytoplasm in alkaline environments Low membrane permeability keeps H from leaving Keeps pH inside cell constant Active pH control with protein pumps pumping in H to their cells o Osmotic Adaptations Halophile Organism requiring at least 2M of salt NaCl for growth Found in brine pools Organism that thrives under high sugar concentrations Osmophile Difficulties High sugar salt concentration o Problem o Solution High solute concentration hypertonic environments causes the cell to shrivel Osmoprotectants help cells survive osmotic stress Osmoregulation regulation of osmotic pressure within the organism o Other adaptations Endolith Hypolith endolith Xerophile Difficulties Organism lives in microscopic spaces within rocks Organism lives inside rocks in cold deserts Hypolith is an Organism that can thrive in dry desiccating environments Such as in Atacama Desert in South America High osmotic stress or dry environments o Less water less life goes back to variable the prevents growth and survival of life o Water Activity Aw Defined as the partial vapor pressure of water in a substance over the partial vapor pressure of pure water at the same temperature Places of high water activity will diffuse to places with low water Low Aw Low water Less microorganisms store food longer Xerophiles can survive in places with Aw 0 8 Fungi 0 7 activity Bacteria 91 o Adaptations to radiation and pressure Piezophile Organism thrives in area with high hydrostatic pressure Found in deep terrestrial subsurface and oceanic trenches Radioresistant Organism resistant to high levels of ionizing radiations mostly ultraviolet but some nuclear Difficulties High Hydrostatic Pressure o Problems o Solutions Cell membrane loses fluidity and becomes impermeable to nutrients Make polyunsaturated fatty acids allowing more fluidity in membrane under pressure UV Light and radioactive radiation causes DNA damage o Solution Repairing enzymes photoreactivating enzymes help recover damaged DNA High Radiation o Problems Sole source of carbon is CO2 and gains energy from inorganic redox reactions reduced minerals pyrite Active in geochemical cycling process that takes place in the earth s surface and subsurface that allows elements to separate or condense and the weathering of parent bedrock to form soil Organism that thrives in nutrient deficient environments Ex Oligotropgic gyre in the pacific Oligotroph Able to tolerate high levels of dissolved metals in solution such as cadmium arsenic copper zinc o Nutrition Adaptations Lithoautotrophs o Toxicity Adaptations Metalotolerant Difficulties Problem Solution o Heavy metals denature proteins o Sulfide production precipitate metal sulfide o Production of organic compounds citric acid for chelation citric acid would combine with metal and make inactive o Uptake and accumulation o Transformation into non toxic forms removing or adding ions Hg2 Hg Polyextremophiles o Able to withstand multiple extreme conditions o Deinococcus Radiodurans Survive radiation cold dehydration vacumn acid toughest Uses oxygen to derive energy from organic compounds soil o Tardigrades Can be found in almost every habitat on earth Consider aquatic bc need it for gas exchange and prevent Can be found on lichen mosses sand dunes soil sediments leaf Can survive endless amounts of extreme environments even in Can start stop metabolic activity cryptobiosis Curls into tun ball when in dry periods and can be revived depends how long cryptobiosis bacteria feces meat desiccation litter space o Places to study extremophiles Hydrothermal vents hot up to 400C Ocean floor Brine pools high salinity Deep sea high pressure Polar cold environment temp below freezing Deep biosphere drilling