Exoplanetary Exoplanetary environments to harbour environments to harbour extremophile life as we extremophile life as we don´t know itdon´t know it

Claudia LAGEClaudia LAGElage@biof.ufrj.brlage@biof.ufrj.br

Instituto de Biofísica Carlos Chagas FilhoInstituto de Biofísica Carlos Chagas FilhoUniversidade Federal do Rio de Janeiro/BrazilUniversidade Federal do Rio de Janeiro/Brazil

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Outline

General surviving strategies to extreme environments found in micro-organisms

Deinococcus, a radiation survivor

Searching for new extremophiles on Earth

Concerns on the Panspermia connection with life as we don´t know it

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The quest for perfect DNA duplication involves a protein complex

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Hyperthermophilic organisms mixed functions of an entire protein complex in a single protein

DNA primaseDNA helicaseDNA polymerase

Rossi et al., J Bacteriol, 2003

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Stronger surface charges cause hyperthermophilic proteins to stabilise complexes under higher temperatures

Archaeal PCNA

Yeast PCNA

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Low-temperature dependence for cold-loving species growth

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Membrane lipid structure in mesophilic organisms

Membrane lipid structure in cold-loving micro-organisms

Low-temperature adaption of cold-loving species membranes

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Solvent (concentration)log Pow

Staphylococcus sp. strain ZZ1

B. cereus strain ZZ2

B. cereus strain ZZ3

B. cereus strain ZZ4

Hexane 100 mM [1.3% (v/v)] 3.5 +++ +++ +++ +++

Cyclohexane 100 mM [1% (v/v)] 3.2 +++ +++ +++ +++

p-Xylene 100 mM [1.2% (v/v)] 3.0 +++ - ± -

Toluene 50 mM [0.53% (v/v)] 2.5 +++ +++ +++ +++

Toluene 100 mM [1% (v/v)] 2.5 +++ ± +++ +++

1-Heptanol 100 mM [1.4% (v/v)] 2.4 - - - -

Dimethylphthalate 100 mM [2% (v/v)] 2.3 +++ - +++ +++

Fluorobenzene 100 mM [1% (v/v)] 2.2 +++ +++ +++ +++

Benzene 100 mM [1% (v/v)] 2.0 +++ +++ +++ +++

Phenol 20 mM [0.18% (v/v)] 1.5 +++ - +++ +++

+++ growth overnight (16 h); ± minimal growth overnight; - no growth

Isolation and characterization of novel organic solvent-tolerant bacteria, Zahir et al. Extremophiles 2005 Oct

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Oceans of organic compounds are present in exoplanets and their moons... e.g. Titan

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They have been here since the beginning (chlorophyll-containing fossilisations in ~2,5Gyr Australian estromatolites)

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ORIGINS OF LIFE ON EARTHS

HOW CLOSE ARE WE TO MICRO-ORGANISMS?

STRESS RESPONSES ARE ALWAYS UP-TO-DATE!

Silicibacter sp.

Homo sapiens

ww

w.n

cbi.n

lm.n

ih.g

ov/B

LAST

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What´s up there in outer space?

No heat

No gases

No water

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Ejection Reentry

Transport

Density: 1 to 106 molecules.cm-3

Pressure > 10-17 atm

Radiation UV: 122.3 J.m-2.s-1

Temperature = 0 to hundreds K

Panspermia

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Horneck et al., Adv Space Res, 1994

Bacterial SPORES were shown to survive a 6-yr exposure to low Earth orbit radiation

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Mineral deposit on rockAvenca ???

Observation may be confusing in the search for life…

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About Deinococcus...

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• The radiation constraint…

• 4Gy gamma rays to humans = • 15.000Gy gamma rays to

radiodurans

•

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SIMULATION EXPERIMENT IN THE SINCHROTRON LIGHT NATIONAL LABORATORY, Campinas, Brazil

CELL POWDER+

HIGH VACUUM+

WHITE BEAM VUV SOLAR RADIATION

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http://microbialgenomics.energy.gov/primer/featured_bugs.shtml

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Superfície microscópicada fita de carbono

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100µm

Morphologic comparison between surfaces of Concordia 2002 micrometeorite (Antartica) and that of the carbon tape on which bacterial powder was layered for irradiation (with permission of M. Maurette)..

CONCORDIA MICROMETEORITES CARBON TAPE

1/

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Viability of Deinococcus radiodurans under shielding conditions

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Multiple secondary radiation effects enhance energy absorption by a large rock fragment

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Micro-sized particles have lower probability to interact with radiation

ATACAMA has life and you don´t see it

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0

5

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Stromatolite Mats Mats Water table Well

Phylogenetic group

%

Alfa

Beta

Gamma

Cf

SRB

Arch

Eub

Sítio Maria Elena – Atacama - Chile

Marte

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WATER ICE UPON MARS LANDING OF PHOENIX!!!

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Searching for novel radiation resistant micro-organisms !!!

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Growth curves after 300J.m-2 UV (single dose)

0,01

0,1

1

10

100

1000

0 3 6Days after UV

N/N

0

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136-D

Growth curves of control cultures

0,01

0,1

1

10

100

1000

0 3 6 Days

N/N

o

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136-D

UV (254nm) survival of bacterial isolates fromAntarctic samples

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KOISTRA et al., 1958:

The behaviour of microorganisms under simulated Martian environmental conditions.

- low pressure chamber (0.06 mbar);

- soil samples from distinct geographic regions (in natura specific microflora);

- initial counts of colonies and after 1, 2 and 3 months under martian conditions;

- environmental “simulation” = cycles of 9h at 25oC, then 15h at -22oC.

Results:

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Surface temperature estimates for some known exoplanets

• The surface temperature estimation depends not only on the stellar temperature but also e.g. on the planet's albedo and atmospheric chemical composition which will define the extent of the greenhouse effect and on how the heat is distributed around the planet

• The present sample of known exoplanets is strongly biased: e.g., long period planets are much more difficult to detect.

• Surface temperatures of the known exoplanets are on the average higher than for planets in the Habitable Zone (HZ)

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– Surface temperatures of a number of Neptune-like planets have been estimated (e.g., Rivera et al. 2005, Bonfils et al. 2005; Bonfils et al. 2007; Demory et al. 2007)

– They are supposedly mainly composed of icy/rocky material, being formed without or having lost the extended gaseous atmosphere

– Some of them have orbital periods between 2 and 6 days and surface temperature ranges from 400 to 700 K

– Even in these particular cases, extremophiles existing on Earth (hyperthermophiles) could live even in the coldest of them

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MOST FAVOURABLE KNOWN CASE:

Gliese 581c (Udry et al. 2007)

A 5 MEarth planet in the HZ of a MV (red) star

For Earth-like or Venus-like albedos, the surface temperature of Gliese 581c is estimated to range between

270 and 313 K, respectively.

Many extremophiles could live under these conditions!

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INTERESTING POSSIBILITY: moons of planets in the HZ

Jupiter-like planets in the HZ: Examples:HD10697 (G5V ; 6.35 MJ, 1072 d orbit) TS 264 K

HD37124 (G4V ; 1.04 MJ, 155.7 d orbit) TS 327 K

HD134987 (G5V ; 1.58 MJ, 260 d orbit) TS 315 K

HD177830 (K2IV ; 1.22 MJ, 392 d orbit) TS 362 K

HD222582 (G3V ; ?? MJ, 576 d orbit) TS 234 K

Extremophiles could live “confortably” under these temperatures

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SUMMARY OF KEY POINTS

The flux of solid material (large dust meteoroids) arriving on Earth from nearby stars was estimated in detail by Murray et al. (2004) from radar detections: ~ 10 yr-1·km-2; estimates on the amount of micro-sized material coming to Earth point to 10,000 TONS/YR !!!

We are presently located in an inter-arm (relatively low-density) region of the Galaxy. Each ~70 to 140 million years the solar system traverses a spiral arm region of much higher stellar and gas density. At each crossing of the Sun through a spiral arm, the flux of dust and gas of extra-solar origin arriving on top of terrestrial atmosphere will increase by many orders of magnitude.

The Panspermia hypothesis might thus be much more efficient. Microbes coming from other places in the CONTAMINATED GALAXY could use dust grains and micrometeorites as natural vehicles and benefit of the shielding effect operated by MICROPARTICULATE material. Living organisms could have more intensively seeded Earth during crossings of the solar system through dense galactic regions because of shorter times required for any organism to reach Earth.

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IN CONCLUSION,

Micro-organisms could function as “minimal” biological organization spreading life in many planetary systems.

Microbial life could give birth to complex life, upon reaching a minimally viable planet/moon.

The ability of extremophile organisms to cope with environmental conditions far beyond conceivable limits should broaden the astronomical concept of HABITABLE ZONE to a biological one, the EXTREMOPHILE ZONE (EZ).

B

Brazilian team:

MSc Ivan PAULINO-LIMADr. João Alexandre R. G. BARBOSA1

Dr. Arnaldo Naves de BRITO1

Prof. Dr. Eduardo JANOT-PACHECO3

Dr Douglas GALANTE3

Gabriel DALMASO

1Laboratório Nacional de Luz Síncrotron – MCT/CNPq 2Instituto de Física – IF/UFRJ3Departamento de Astronomia – IAG/USP

International co-operation:Dr. Nigel MASON, Open University, UKDr. Charles COCKELL, Open University, UKArmando AZUA-BUSTOS, Univ Católica Chile

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KEEP WATCHING...

Absence of evidence is not evidence of absence

Considering the immense Universe and the infinity of time, it is a joy for me to share a planet and a time with you…

Carl Sagan

THANK YOU

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