©2004 howard hughes medical institute extremophiles 101 mark e. nielsen, ph.d. science education...

©2004 Howard Hughes Medical Institute

Extremophiles 101

Mark E. Nielsen, Ph.D.

Science Education Fellow Educational Resources Group

Howard Hughes Medical Institute

[email protected] www.biointeractive.com

©2004 Howard Hughes Medical Institute 6 July 2012

Extremophiles 101 – Astrobiology Laboratory Institute for Instructors

Outline for today’s talk

Introduction and few definitions

Tour of extreme environments• biological ramifications• coping mechanisms• interesting highlights

Practical implications/considerations



What is normal and what is extreme?

Physical extremes: - Temperature - Pressure - Radiation

Geochemical extremes: - pH (acidity levels) - Salinity - Desiccation - Oxygen species - Redox potential

For any particular property (T, pH, salinity) extreme values are values far from the typical range for human life



Why cover extremophiles in an astrobiology workshop?

Mars Europa



DiversityWho are the extremophiles?



Environmental Extremes – What do they mean to the organisms?

Temperature

protein denaturation, reduced solubility of gases,Increases fluidity of membranes, chlorophyll degrades at 75 °C

ice formation (physical stress), lack of liquid water (chemical stress)



Cell membranes

Membrane fluidity is related to composition of fatty acids



Other high temperature adaptations

Histones – proteins that bind to DNA

Different chemical bonds




Radiation = Energy in transit as particles (e.g., electrons, neutrons, protons, alpha particles) or waves (gamma rays, x-rays, UV)

Rarely occur but high UV exposure can occurDNA damage directly or indirectly from ROS

Deinococcus radiodurans"A lethal level of radiation for humans is about 700 rads. The bacterium Deinococcus radiodurans can withstand 1.5 million... There’s never been anything like this level of natural radioactivity on earth in its 4.6 billion year history, so how can we explain the evolution of such a capability?"



Reactive Oxygen Species

Early Earth may have had H2O2 rain

Organisms evolved anti-oxidants to deal with this

• super oxide dismutase/reductase

• catalase• peroxidase

Oxygen is very corrosive to organic chemical bonds. Mechanisms evolved very early to deal with this




Pressure:Boiling pt. of water increasesVolume changesGravity – changes in biomass production rates, changes in membrane permeability



Environmental Extremes

Desiccation:

Water is an unusual fluid that makes it unique and critical for life.

Issues: irreversible phase changes to lipids, proteins, and nucleic acids through denaturation and chemical reactions (Maillard reactions)




pH

Lots of H+ can denature proteins (ceviche)

Acidophiles thrive at low pH

Alkaliphiles thrive at high pH (an equally challenging environment) protons are scarce so energy tough to come by Ferroplasma acidarmanus




pH

Lots of H+ can denature proteins (ceviche)

Acidophiles thrive at low pH

Alkaliphiles thrive at high pH (an equally challenging environment) protons are scarce so energy tough to come by




Salinity

Halophiles – organisms with adaptations to grow in high salt conditions (up to saturation!).

Adaptation: Increasing osmotica intracellularly (e.g., K+, betaine, glutamate, sucrose)

Dunaliella salinaHalobacterium (actually Archaea)



Summary of extremophiles and their environments



Biotechnological relevanceProcess Biomolecule Advantage Source

PCR Reaction Taq polymeraseStable at high temperatures

Thermophiles

Paper bleaching xylanasesDecreases amount of bleach required

Thermophiles

Degradation of polymers in detergents

ProteasesAmylases Lipases

Improved performance of detergents and stable at high pH

Psychrophiles and alkaliphiles

Cheese maturation and dairy processing

ProteasesStable at low temperatures

Psychrophiles

Biofuel production CellulasesStable at high temp. versatile

Thermophiles

Biofuel production Fatty acids/lipidsStable at high temp/low pH

Thermophilic microalgae



Biotechnological relevance

Thermus aquaticus – DNA polymerase



Biofuels – A challenge and an opportunity




Bioelectrosynthesis

Microbes can accept electrons from solid surfaces to fix carbon



Bringing it back to astrobiology



Lake Vostoc: A model for Life on Europa?



A good Source

Nature, Vol. 409, February 2001



Questions? temperatures as low as -200 °C (-328 °F) and as high as 151 °C (304 °F);

freezing and/or thawing processes;

changes in salinity;

lack of oxygen;

lack of water;

levels of X-ray radiation 1000x the lethal human dose;

some noxious chemicals;

boiling alcohol;

low pressure of a vacuum;

high pressure (up to 6x the pressure of the deepest part of the ocean)

©2004 howard hughes medical institute extremophiles 101 mark e. nielsen, ph.d. science education...

Documents

cover extremophiles

astrobiology workshop

instructors diversity

physical extremes

human life slide

salinity extreme values

mars europa slide

radiation geochemical