Extremophiles

Life on edge

Life at High Temperatures, Thomas M. Brock

Extremophiles

Images from NASA, http://pds.jpl.nasa.gov/planets/

Extraterrestrial microbial life-does it exist?

Lecture Aims

What are Extremophiles- an introduction Strategies for growth & survival Biotechnology

Introduction to Extremophiles What are Extremophiles

Live where nothing else can How do they survive?

Extremozymes (more details later) Why are they are interesting?

Extremes fascinate us Life on other planets Life at boiling temperatures

Practical applications are interesting Interdisciplinary lessons

Genetic Prospecting

Extremophile Definition - Lover of extremities History

First suspected in 1950’s Extensively studied since 1970’s

Temperature extremes Boiling or freezing, 1000C to -10C Chemical extremes Vinegar or ammonia (<5 pH or >9 pH) Highly saline, up to x10 sea water

How we sterilize & preserve foods today

Extreme Temperatures

Thermophiles - High temperature Thermal vents and hot springs May go hand in hand with chemical

extremes

Psychrophiles - Low temperature Arctic and Antarctic

1/2 of earth’s surface is oceans between 1-40C

Deep sea –10C to 40C Most rely on photosynthesis

Thermophiles

Hydrothermal Vents- Black smokers at 350 oC

Obsidian Pool,Yellowstone National Park

Psychrophiles

Chemical Extremes

Acidophiles - Acidic Again some thermal vents & hot springs

Alkaliphiles - Alkaline Soda lakes in Africa and Western U.S.

Halophiles - Highly saline Natural salt lakes and manmade pools Sometimes occurs with extreme

alkalinity

Acidophiles

pH 0-1 of watersat Iron Mountain

Alkaliphiles

Mono Lake- alkalinesoda lake, pH 9 &salinity 8%

Halophiles

Dead Sea

Great Salt Lake coastalsplash zones

Solar salterns Owens Lake

Survival Temperature extremes

Every part of microbe must function at extreme

“Tough” enzymes for Thermophiles “Efficient” enzymes for Psychrophiles

Many enzymes from these microbes are interesting

Life at High Temperatures, Thomas M. Brock

Survival Chemical extremes

Interior of cell is “normal” Exterior protects the cell

Acidophiles and Alkaliphiles sometimes excrete protective substances and enzymes

Acidophiles often lack cell wall Some moderate halophiles have high concs

of a solute inside to avoid “pickling” Some enzymes from these microbes are

interesting

What are enzymes? Definition - a protein that catalyses

(speeds up) chemical reactions without being changed

What are enzymes? Enzymes are specific

Lock and key analogy

Enzyme

Substrate A

Product B

Product C

What are enzymes? Activation energy

Enzymes allow reactions with lower energyEn

erg

y

Time

Without Enzyme

With Enzyme

What are enzymes? Enzymes are just a protein

They can be destroyed by Heat, acid, base

They can be inhibited by Cold, salt

Heat an egg white or add vinegar to milk Protein is a major component of both-

denatures

Practical Applications Extremozymes

Enzyme from Extremophile Industry & Medicine

What if you want an enzyme to work In a hot factory? Tank of cold solution? Acidic pond? Sewage (ammonia)? Highly saline solution?

One solution Pay a genetic engineer to design a

“super” enzymes... Heat resistant enzymes Survive low temperatures Able to resist acid, alkali and/or salt

This could take years and lots of money

Extremophiles got there first Nature has already given us the

solutions to these problems Extremophiles have the enzymes

that work in extreme conditions

Endolithic algae from Antarctica; Hot springs in Yellowstone National Park, © 1998 Reston Communications, www.reston.com/astro/extreme.html

Thermophiles Most interesting, with practical applications

Many industrial processes involve high heat 450C (113F) is a problem for most enzymes First Extremophile found in 1972

Life at High Temperatures, Thomas M. Brock

PCR - Polymerase Chain Reaction

Allows amplification of small sample of DNA using high temperature process Technique is about 10 years old DNA fingerprints - samples from crime

scene Genetic Screening - swab from the mouth Medical Diagnosis - a few virus particles

from blood Thermus aquaticus or Taq

Life at High Temperatures, Thomas M. Brock

Psychrophiles Efficient enzymes to work in the cold

Enzymes to work on foods that need to be refrigerated

Perfumes - most don’t tolerate high temperatures

Cold-wash detergents

Algal mats on an Antarctic lake bottom, © 1998 Reston Communications, www.reston.com/astro/extreme.html

Acidophiles

Enzymes used to increase efficiency of animal feeds enzymes help animals

extract nutrients from feed

more efficient and less expensive

Life at High Temperatures, Thomas M. Brock

Alkaliphiles

“Stonewashed” pants Alkaliphilic enzymes soften fabric and

release some of the dyes, giving worn look & feel

Detergents Enzymes dissolve proteins or fats Detergents do not inhibit alkaliphilic

enzymes

Halophiles What is a halophile? Diversity of Halophilic Organisms Adptation Strategies

Osmoregulation-“Compatible Solute” Strategy

“Salt-in” Strategy

Interesting Facts and Applications

What is a halophile? Halophile = “salt loving; can grow in higher

salt concentrations Based on optimal saline environments

halophilic organisms can be grouped into three categories: extreme halophiles, moderate halophiles, and slightly halophilic or halotolerant organisms

Some extreme halophiles can live in solutions of 25 % salt; seawater = 2% salt

Diversity of Halophilic Organisms

Halophiles are a broad group &t can be found in all three domains of life.

Found in salt marshes, subterranean salt deposits, dry soils, salted meats, hypersaline seas, and salt evaporation ponds.

Unusual Habitats A Pseudomonas species lives on a

desert plant in the Negev Desert- the plant leaves secretes salt through salt glands.

A Bacillus species is found in the nasal cavities of desert iguanas- iguanas nasal cavities have salt glands which secrete KCl brine during osmotic stress.

Osmoregulation Halophiles maintain an internal

osmotic potential that equals their external environment.

Osmosis is the process in which water moves from an area of high concentration to an area of low concentration.

Osmoregulation In order for cells to maintain their water

they must have an osmotic potential equal to their external environment.

As salinity increases in the environment its osmotic potential decreases.

If you placed a non halophilic microbe in a solution with a high amount of dissolved salts the cell’s water will move into the solution causing the cell to plasmolyze.

Osmoregulation Halophiles have adapted to life at high

salinity in many different ways. Structural modification of external cell

walls- posses negatively charged proteins on the outside which bind to positively charged sodium ions in their external environments & stabilizes the cell wall break down.

“Compatible Solute” Strategy

Cells maintain low concentrations of salt in their cytoplasm by balancing osmotic potential with organic, compatible solutes.

They do this by the synthesis or uptake of compatible solutes- glycerol, sugars and their derivatives, amino acids and their derivatives & quaternary amines such as glycine betaine.

Energetically synthesizing solutes is an expensive process. Autotrophs use between 30 to 90 molecules of

ATP to synthesize one molecule of compatible solute.

Heterotrophs use between 23 to 79 ATP.

“Salt-in” Strategy Cells can have internal concentrations

that are osmotically equivalent to their external environment.

This “salt-in” strategy is primarily used by aerobic, extremely halophilic archaea and anaerobic bacteria.

They maintain osmotically equivalent internal concentrations by accumulating high concentrations of potassium chloride.

“Salt-in” Strategy Potassium ions enter the cell

passively via a uniporter. Sodium ions are pumped out. Chloride enters the cell against the membrane potential via cotransport with sodium ions.

For every three molecules of potassium chloride accumulated, two ATP are hydrolyzed making this strategy more energy efficient than the “compatible solute” strategy.

“Salt-in” Strategy To use this strategy all enzymes and

structural cell components must be adapted to high salt concentrations to ensure proper cell function.

Halobacterium: an extreme halophile Halobacterium are members of domain

archaea. Widely researched for their extreme

halophilism and unique structure. Require salt concentrations between

15% to saturation to live. Use the “salt-in” strategy. Produce ATP by respiration or by

bacteriorhodopsin.

Halobacterium May also have halorhodopsin that

pumps chloride into the cell instead of pumping protons out.

The Red Sea was named after halobacterium that turns the water red during massive blooms.

Facts

The term “red herring” comes from the foul smell of salted meats that were spoiled by halobacterium.

There have been considerable problems with halophiles colonizing leather during the salt curing process.

Applications

The extraction of carotene from carotene rich halobacteria and halophilic 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.

Applications Other possible applications being

explored: Increasing crude oil extraction (MEOR) Genetically engineering halophilic

enzymes encoding DNA into crops to allow for salt tolerance

Treatment of waste water (petroleum)

Conclusions Halophiles are salt tolerant organisms. They are widespread and found in all

three domains. The “salt-in” strategy uses less energy

but requires intracellular adaptations. Only a few prokaryotes use it.

All other halophiles use the “compatible solute” strategy that is energy expensive but does not require special adaptations.

Genetic prospecting

What is it? Think of a hunt for the genetic gold

Summary Now you know something about

Extremophiles Where they live & how they survive

They are interesting because They have enzymes that work in

unusual conditions The practical applications are

interesting