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1、ExtremophilesLife on the edge Life at High Temperatures, Thomas M. Brock.ExtremophilesImages from NASA, http:/pds.jpl.nasa.gov/planets/.GoalsuOverview of ExtremophilesReview some biologyGive some applicationsMotivate you to study Microbiology!.Introduction to ExtremophilesuWhat are they?Microbes liv
2、ing where nothing else can uHow do they survive?ExtremozymesuWhy are they are interesting?Extremes fascinate usuLife on other planetsPractical applications are interestingInterdisciplinary lessonsGenetic Prospecting.Extremo - phileuDefinition - Lover of extremesuHistorySuspected about 30 years agoKn
3、own and studied for about 20 yearsuTemperature extremesboiling or freezing, 1000C to -10C (212F to 30F) uChemical extremesvinegar or ammonia (9 pH)highly salty, up to ten times sea wateruHow we sterilize & preserve foods today.Extreme TemperaturesuThermophiles - High temperatureThermal vents and hot
4、 springsMay go hand in hand with chemical extremesuPsychrophiles - Low temperatureArctic and Antarctic1/2 of Earths surface is oceans between 10C & 40CDeep sea 10C to 40CMost rely on photosynthesis.ThermophilesObsidian Pool,Yellowstone NationalParkHydrothermal Vents.Psychrophiles.Chemical ExtremesuA
5、cidophiles - AcidicAgain thermal vents and some hot springsuAlkaliphiles - AlkalineSoda lakes in Africa and western U.S.uHalophiles - Highly Salty Natural salt lakes and manmade poolsSometimes occurs with extreme alkalinity.AcidophilespH 0-1 of watersat Iron Mountain.Alkaliphilee.g. Mono Lakealkalin
6、e soda lake, pH 9salinity 8%.Halophilessolar salternsOwens Lake, Great Salt Lakecoastal splash zonesDead Sea.SurvivaluTemperature extremesEvery part of microbe must function at extreme“Tough” enzymes for Thermophiles “Efficient” enzymes for Psychrophiles Many enzymes from these microbes are interest
7、ingLife at High Temperatures, Thomas M. Brock.SurvivaluChemical extremesInterior of cell is “normal”Exterior protects the cellAcidophiles and Alkaliphiles sometimes excrete protective substances and enzymesAcidophiles often lack cell wallSome moderate halophiles have high concentrations of a solute
8、inside to avoid “pickling”Some enzymes from these microbes are interesting.What are enzymes?uDefinition - a protein that catalyses (speeds up) chemical reactions without being changed.What are enzymes?uEnzymes are specificLock and key analogyEnzymeSubstrate AProduct BProduct C.What are enzymes?uActi
9、vation energyEnzymes allow reactions with lower energyEnergyTimeWithout EnzymeWith Enzyme.What are enzymes?uEnzymes are just a proteinThey can be destroyed byHeat, acid, baseThey can be inhibited byCold, saltuTry doing this with an egg white or milkProtein is a major component of both.Practical Appl
10、icationsuExtremozymesEnzyme from ExtremophileuIndustry & MedicineuWhat if you want an enzyme to work In a hot factory?Tank of cold solution?Acidic pond?Sewage (ammonia)?Highly salty solution?.One solutionuPay a genetic engineer to design a “super” enzymes.Heat resistant enzymesSurvive low temperatur
11、esAble to resist acid, alkali and/or saltuThis could take years and lots of money.Extremophiles got there firstuNature has already given us the solutions to these problemsExtremophiles have the enzymes that work in extreme conditionsEndolithic algae from Antarctica; Hot springs in Yellowstone Nation
12、al Park, 1998 Reston Communications, interesting practical applications so farMany industrial processes involve high heat450C (113F) is a problem for most enzymesFirst Extremophile found 30 years agoLife at High Temperatures, Thomas M. Brock.PCR - Polymerase Chain ReactionuAllows amplification of s
13、mall sample of DNA using high temperature processTechnique is about 10 years oldDNA fingerprints - samples from crime sceneGenetic Screening - swab from the mouthMedical Diagnosis - a few virus particles from blood uThermus aquaticus or TaqLife at High Temperatures, Thomas M. Brock.PsychrophilesuEff
14、icient enzymes to work in the coldEnzymes to work on foods that need to be refrigeratedPerfumes - most dont tolerate high temperaturesCold-wash detergentsAlgal mats on an Antarctic lake bottom, 1998 Reston Communications, used to increase efficiency of animal feedsenzymes help animals extract nutri
15、ents from feedmore efficient and less expensiveLife at High Temperatures, Thomas M. Brock.Alkaliphilesu“Stonewashed” pantsAlkaliphilic enzymes soften fabric and release some of the dyes, giving worn look and feeluDetergentsEnzymes to dissolve proteins or fatsAlkaliphilic enzymes can work with deterg
16、ents.HalophilesuWhat is a halophile?uDiversity of Halophilic OrganismsuOsmoregulationu“Compatible Solute” Strategyu“Salt-in” StrategyuInteresting Facts and Applications.What is a halophile?uThe word halophile means “salt loving”.uA halophile is an organism that can grow in higher salt concentrations
17、 than the norm.uBased on optimal saline environments halophilic organisms can be grouped into three categories: extreme halophiles, moderate halophiles, and slightly halophilic or halotolerant organisms.uSome extreme halophiles can live in solutions of 35 % salt. This is extreme compared to seawater
18、 which is only 3% salt.Diversity of Halophilic OrganismsuHalophiles are a broad group that can be found in all three domains of life.uThey are found in salt marshes, subterranean salt deposits, dry soils, salted meats, hypersaline seas, and salt evaporation pools.Unusual HabitatsuThe bacterium pseud
19、omonas was found living on a desert plant in the Negev Desert. The plant secretes salt through salt glands on its leaves.uBacillus was found in the nasal cavities of desert iguanas. These iguanas have salt glands in their nasal cavities that secrete KCl brine during osmotic stress.OsmoregulationuLiv
20、ing in high salinity poses a serious stress that halophiles have overcome through special processes or adaptations.uThe stress lies in the microbes ability to maintain an internal osmotic potential that equals their external environment.uOsmosis is the process in which water moves from an area of hi
21、gh concentration to an area of low concentration.OsmoregulationuIn order for cells to maintain their water they must have an osmotic potential equal to their external environment.uAs salinity increases in the environment its osmotic potential decreases.uIf you placed a non halophilic microbe in a so
22、lution with a high amount of dissolved salts the cells water will move into the solution causing the cell to plasmolyze.OsmoregulationuHalophiles have adapted to life at high salinity in many different ways.uOne way is through the modification of their external cell walls. They tend to have negative
23、ly charged proteins on the outside of their cell walls that stabilize it by binding to positively charged sodium ions in their external environments. If salt concentrations decline their cell walls may become unstable and break down.“Compatible Solute” StrategyuThere are two strategies that halophil
24、es have evolved to deal with high salt environments.uIn the “compatible solute” strategy cells maintain low concentrations of salt in their cytoplasm by balancing osmotic potential with organic, compatible solutes.uThey do this by the synthesis or uptake of compatible solutes.“Compatible Solute” Str
25、ategyuCompatible solutes include polyols such as glycerol, sugars and their derivatives, amino acids and their derivatives, and quaternary amines such as glycine betaine.uEnergetically this is an expensive process.uAutotrophs use between 30 to 90 molecules of ATP to synthesize one molecule of the co
26、mpatible solutes. Heterotrophs use between 23 to 79 ATP.“ Compatible Solute” StrategyuEnergy is also expended in pumping out salts that dissolve into the cell.uThe uptake of available compatible solutes in the environment is an adaptation they have evolved to reduce the energy cost of living in high
27、 salt concentrations.“Salt-in” StrategyuCells can have internal concentrations that are osmotically equivalent to their external environment.uThis “salt-in” strategy is primarily used by aerobic, extremely halophilic archaea and anaerobic bacteria.uThey maintain osmotically equivalent internal conce
28、ntrations by accumulating high concentrations of potassium chloride.“Salt-in” StrategyuPotassium ions enter the cell passively via a uniport system. Sodium ions are pumped out. Chloride enters the cell against the membrane potential via cotransport with sodium ions.uFor every three molecules of pota
29、ssium chloride accumulated, two ATP are hydrolyzed making this strategy more energy efficient than the “compatible solute” strategy.“Salt-in” StrategyuTo use this strategy all enzymes and structural cell components must be adapted to high salt concentrations to ensure proper cell function.Halobacter
30、ium: an example of an extreme halophileuHalobacterium are members of the halophile group in the domain archaea. They are widely researched for their extreme halophilism and unique structure.uThey require salt concentrations between 15% to 35% sodium chloride to live.uThey use the “salt-in” strategy.
31、uThey produce ATP by respiration or by bacteriorhodopsin.HalobacteriumuThey may also have halorhodopsin that pumps chloride into the cell instead of pumping protons out.uThe Red Sea was named after halobacterium that turns the water red during massive blooms. Facts uThe term “red herring” comes from
32、 the foul smell of salted meats that were spoiled by halobacterium.uThere have been considerable problems with halophiles colonizing leather during the salt curing process.ApplicationsuCurrent applications using halophiles include:the extraction of carotene from carotene rich halobacteria and haloph
33、ilic algae that can then be used as food additives or as food-coloring agents.the use of halophilic organisms in the fermentation of soy sauce and Thai fish sauce.ApplicationsuMany possible applications using halophiles are being explored such as:increasing crude oil extractiongenetically engineerin
34、g halophilic enzyme encoding DNA into crops to allow for salt tolerancetreatment of waste water.ConclusionsuHalophiles are salt tolerant organisms.uThey are widespread and found in all three domains.uThe “salt-in” strategy uses less energy but requires intracellular adaptations. Only a few prokaryot
35、es use it.uAll other halophiles use the “compatible solute” strategy that is energy expensive but does not require special adaptations.Genetic prospectinguWhat is it?Think of a hunt for the genetic goldPr. Patrick Forterre, Extremophiles Laboratory of IGM at Orsay, France http:/www-archbac.u-psud.fr/.SummaryuNow you know something about ExtremophilesWhere they live & how they surviveuThey are interesting becauseThey have enzymes that work in unusual conditionsThe practical applications are interesting.
