Microbial Life in Extreme Environments Thermophiles Slide 1:Title slide. Slide 2:Examples of hot zones:Yellowstone National Park hot spring,hydrothermal vent, compost pile,and the deep Earth Slide 3:movie clip from the Mid-Cayman Rise Hydrothermal vent system.This is the deepest hydrothermal vent system known at about 5 km depth.Perhaps a window into deep subsurface microbial life? Slide 4:Image of Earth's tectonic plates that connect to one another in various ways (convergent-one moves under another,divergent-they both move away from one another,and transform-they move alongside one another). Slide 5:Mantle convection cells move the plates around.In the mantle hot material rises towards the crust.When it reaches the base of the crust it cools and sinks back down through the mantle This slow but incessant movement in the mantle causes the rigid tectonic plates to move (float) around the earth surface (at an equally slow rate). Slide 6:Heat rising from deep within the earth produces fumaroles and solfataras.Fumaroles are a geothermally heated opening in the Earth where steam and hot gases are expelled. Solfataras(Italian name)are a relatively cool type of fumarole(between 100C and 300C)that gives off hydrogen sulfide that reacts with the oxygen in the air to produce sulfur deposits. Slide 7:There are two basic types of hydrothermal vents.They come in very different chemistries.Black smokers produce lots of sulfur minerals that make dark plume.Their chimneys are made of calcium sulfate and metal sulfides.White smokers produce barium, calcium and silicon precipitates which form a white plume.Their chimneys are made of calcium carbonate.Lost City in the Mid-Atlantic Ridge produces white smokers.Reactions between seawater and upper mantle peridotite produce methane-and hydrogen-rich fluids that are highly alkaline(pH 9 to 11),with temperatures ranging from <40 to 90C. Slide 8:Some additional notable features of hydrothermal vents.The first vent paper:Lonsdale, P.(1977)."Clustering of suspension-feeding macrobenthos near abyssal hydrothermal vents at oceanic spreading centers".Deep Sea Research 24(9):857.No one on this geology cruise expected to discover new species,but they did!Supercritical fluids refer to a phase of water having both gas and liquid properties.They are formed at high temperature and high pressure, such as within certain hydrothermal vents.In 1992 a paper was published called The Deep Hot Biosphere by Thomas Gold.It suggested that life could extend far below hydrothermal vents. This hypothesis is still of great interest today.Mining vents?They contain polymetallic sulfides. Some of the metals are quite valuable and some companies would like to mine them
Microbial Life in Extreme Environments Thermophiles Slide 1: Title slide. Slide 2: Examples of hot zones: Yellowstone National Park hot spring, hydrothermal vent, compost pile, and the deep Earth. Slide 3: movie clip from the Mid-Cayman Rise Hydrothermal vent system. This is the deepest hydrothermal vent system known at about 5 km depth. Perhaps a window into deep subsurface microbial life? Slide 4: Image of Earth’s tectonic plates that connect to one another in various ways (convergent – one moves under another, divergent – they both move away from one another, and transform – they move alongside one another). Slide 5: Mantle convection cells move the plates around. In the mantle hot material rises towards the crust. When it reaches the base of the crust it cools and sinks back down through the mantle. This slow but incessant movement in the mantle causes the rigid tectonic plates to move (float) around the earth surface (at an equally slow rate). Slide 6: Heat rising from deep within the earth produces fumaroles and solfataras. Fumaroles are a geothermally heated opening in the Earth where steam and hot gases are expelled. Solfataras (Italian name) are a relatively cool type of fumarole (between 100°C and 300°C) that gives off hydrogen sulfide that reacts with the oxygen in the air to produce sulfur deposits. Slide 7: There are two basic types of hydrothermal vents. They come in very different chemistries. Black smokers produce lots of sulfur minerals that make dark plume. Their chimneys are made of calcium sulfate and metal sulfides. White smokers produce barium, calcium and silicon precipitates which form a white plume. Their chimneys are made of calcium carbonate. Lost City in the Mid-Atlantic Ridge produces white smokers. Reactions between seawater and upper mantle peridotite produce methane- and hydrogen-rich fluids that are highly alkaline (pH 9 to 11), with temperatures ranging from <40° to 90°C. Slide 8: Some additional notable features of hydrothermal vents. The first vent paper: Lonsdale, P. (1977). "Clustering of suspension-feeding macrobenthos near abyssal hydrothermal vents at oceanic spreading centers". Deep Sea Research 24 (9): 857. No one on this geology cruise expected to discover new species, but they did! Supercritical fluids refer to a phase of water having both gas and liquid properties. They are formed at high temperature and high pressure, such as within certain hydrothermal vents. In 1992 a paper was published called The Deep Hot Biosphere by Thomas Gold. It suggested that life could extend far below hydrothermal vents. This hypothesis is still of great interest today. Mining vents? They contain polymetallic sulfides. Some of the metals are quite valuable and some companies would like to mine them
Slide 9:OK,now let's think about how these various hot zones relate to microbial life.Note the facts on this slide.Mesophiles have an optimum temperature of 20-45C.Thermophiles have an optimum temperature equal to 45-80C.Hyperthermophile have optimal temperatures greater than 80C.Note that the upper temperature limit for life may be ~150C Slide 10:This is a phylogenetic tree of life.All of the emboldened deeply branching lineages contain thermophilic microbes.This fact along with data on the physical and chemical characteristics of the early earth have led scientists to speculate that life first evolved in a high temperature environment. Slide 11:Prof.Thomas Brock really got much of the interest in thermophilic and hyperthemrophilic microbes started.He did extensive sampling in the hot springs of Yellowstone National Park and isolated many thermophilic microbes.He even isolated and made available to the world the species Thermus aguaticus.A DNA polymerase from this microbe was later used by Dr.Kerry Mullis to develop the polymerase chain reaction.Dr. Mullis received the Nobel Prize for this discovery.Unfortunately,neither the National Park Service nor Dr.Brock received any financial reward or recognition. Slide 12:Dr.Karl Stetter took the study of thermophilic microbes to another level with his "green thumb"for growing microbes and his appreciation for anaerobic microbiology.Most hyperthermophiles are strict anaerobes. Slide 13:Anaerobic microbiology requires very different techniques and equipment from that used with aerobic and facultatively anaerobic microbes.For example,anaerobic hoods (left)and anaerobic gasing stations(right)are often needed to ensure an oxygen free environment. Slides 14-19:examples of some of hyperthermophilic microbes,including the most high temperature-adapted microbes yet known. Slide 18:This slide shows the current world record holder for the upper temperature limit for life:122C.This slide shows a technique for growing this deep-sea methane producing microbe that involves high pressure as well as high temperature. Slide 19:describes a hyperthermophile that uses rocket fuel to grow!It breathes perchlorate.In other words this microbe uses perchlorate as an electron acceptor just like we breath oxygen. Slide 20:This slide outlines a highly controversial study that purported to have discovered hydrothermal vent microbes living at 250C.The flaws in the experiment(noted by Trent et al.) are indicated Slide 21:So how to microbes live at high temperature?One of the explanations is that their proteins having higher temperature limits for denaturation as shown on this plot. Slide 22:Proteins are held together by four different classes of weak bonds as indicated on this slide.You should know what these are.Proteins from thermophilic microbes use all of these weak bonds to keep their proteins more stable
Slide 9: OK, now let’s think about how these various hot zones relate to microbial life. Note the facts on this slide. Mesophiles have an optimum temperature of 20 - 45ºC. Thermophiles have an optimum temperature equal to 45 - 80ºC. Hyperthermophile have optimal temperatures greater than 80ºC. Note that the upper temperature limit for life may be ~ 150ºC Slide 10: This is a phylogenetic tree of life. All of the emboldened deeply branching lineages contain thermophilic microbes. This fact along with data on the physical and chemical characteristics of the early earth have led scientists to speculate that life first evolved in a high temperature environment. Slide 11: Prof. Thomas Brock really got much of the interest in thermophilic and hyperthemrophilic microbes started. He did extensive sampling in the hot springs of Yellowstone National Park and isolated many thermophilic microbes. He even isolated and made available to the world the species Thermus aquaticus. A DNA polymerase from this microbe was later used by Dr. Kerry Mullis to develop the polymerase chain reaction. Dr. Mullis received the Nobel Prize for this discovery. Unfortunately, neither the National Park Service nor Dr. Brock received any financial reward or recognition. Slide 12: Dr. Karl Stetter took the study of thermophilic microbes to another level with his “green thumb” for growing microbes and his appreciation for anaerobic microbiology. Most hyperthermophiles are strict anaerobes. Slide 13: Anaerobic microbiology requires very different techniques and equipment from that used with aerobic and facultatively anaerobic microbes. For example, anaerobic hoods (left) and anaerobic gasing stations (right) are often needed to ensure an oxygen free environment. Slides 14-19: examples of some of hyperthermophilic microbes, including the most high temperature-adapted microbes yet known. Slide 18: This slide shows the current world record holder for the upper temperature limit for life: 122°C. This slide shows a technique for growing this deep-sea methane producing microbe that involves high pressure as well as high temperature. Slide 19: describes a hyperthermophile that uses rocket fuel to grow! It breathes perchlorate. In other words this microbe uses perchlorate as an electron acceptor just like we breath oxygen. Slide 20: This slide outlines a highly controversial study that purported to have discovered hydrothermal vent microbes living at 250°C. The flaws in the experiment (noted by Trent et al.) are indicated. Slide 21: So how to microbes live at high temperature? One of the explanations is that their proteins having higher temperature limits for denaturation as shown on this plot. Slide 22: Proteins are held together by four different classes of weak bonds as indicated on this slide. You should know what these are. Proteins from thermophilic microbes use all of these weak bonds to keep their proteins more stable
Slide 23:Thermophiles also have proteins with fewer asparagines and glutamine,which are prone to breakdown via deamidation at high temperature. Slide 24:There are also extrinsic factors(factors external to the proteins themselves)that help to keep proteins stable.This slide shows 2-D gel analyses of proteins turned on at high temperature Some of these so called heat shock proteins are chaperones,a class of proteins that function by helped other proteins to stay properly folded.Some chaperones also help to refold denatured proteins Slide 25:Heat shock protein 60(hsp 60)is one major type of protein chaperone.It's mode of action is shown on this slide.This type of protein is important for helping proteins at both low temperature and at high temperature.The importance of protein chaperones to life at high temperature is highlighted by the fact that at the stressful high temperature of 108C up to 80% of the protein in the hyperthermophile Pyrodictium occultum consists of just one type of chaperone. Slide 26:There are also small organic molecules that can help to keep proteins folded at high temperature.You don't need to know the formulas but you do need to know the names of these molecules. Slides 27/28:DNA also needs to be stabilized at high temperature.This could be accomplished in theory by altering the GC content.G-C bonds are stronger than A-T bonds.However hyperthermophiles use proteins to stabilize DNA such as the histone-like protein Hmf.In addition,all hyperthermophiles use an enzyme called reverse gyrase to give their DNA a positive supercoil.Somehow positive supercoiling also confers greater thermal stability to the DNA Slides 29/30:Remember there are three domains to life,Bacteria,Eukarya and Archaea.Many hyperthermophiles belong within the domain Archaea and Archaea have very different types of membrane lipids.A single lipid molecule often contains four ether linkages.These confer more stability to the lipid chain than the two ester linkages used in Bacteria and Eukarya.The archaeal lipid chains also contain isoprene units that contain methyl groups sticking out from the plane of the hydrocarbon chain.These methyl groups also confer greater stability to the hydrocarbon
Slide 23: Thermophiles also have proteins with fewer asparagines and glutamine, which are prone to breakdown via deamidation at high temperature. Slide 24: There are also extrinsic factors (factors external to the proteins themselves) that help to keep proteins stable. This slide shows 2-D gel analyses of proteins turned on at high temperature. Some of these so called heat shock proteins are chaperones, a class of proteins that function by helped other proteins to stay properly folded. Some chaperones also help to refold denatured proteins. Slide 25: Heat shock protein 60 (hsp 60) is one major type of protein chaperone. It’s mode of action is shown on this slide. This type of protein is important for helping proteins at both low temperature and at high temperature. The importance of protein chaperones to life at high temperature is highlighted by the fact that at the stressful high temperature of 108ºC up to 80% of the protein in the hyperthermophile Pyrodictium occultum consists of just one type of chaperone. Slide 26: There are also small organic molecules that can help to keep proteins folded at high temperature. You don’t need to know the formulas but you do need to know the names of these molecules. Slides 27/28: DNA also needs to be stabilized at high temperature. This could be accomplished in theory by altering the GC content. G-C bonds are stronger than A-T bonds. However hyperthermophiles use proteins to stabilize DNA such as the histone-like protein Hmf. In addition, all hyperthermophiles use an enzyme called reverse gyrase to give their DNA a positive supercoil. Somehow positive supercoiling also confers greater thermal stability to the DNA. Slides 29/30: Remember there are three domains to life, Bacteria, Eukarya and Archaea. Many hyperthermophiles belong within the domain Archaea and Archaea have very different types of membrane lipids. A single lipid molecule often contains four ether linkages. These confer more stability to the lipid chain than the two ester linkages used in Bacteria and Eukarya. The archaeal lipid chains also contain isoprene units that contain methyl groups sticking out from the plane of the hydrocarbon chain. These methyl groups also confer greater stability to the hydrocarbon