Biosignatures: Linking Life and the Geosphere

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Biosignatures Linking Life and the Geosphere

• P.J. Boston
• Director, Cave Karst Studies Program
• Earth Environmental Sciences Dept.
• New Mexico Tech (NM Inst. Mining Tech.)
• Socorro, NM 87801

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What do microbes do to rocks and minerals?
They transform materials.
Dissolution active mining metabolic
byproducts Corrosion bedrock minerals metals
Nucleation alive dead Precipitation passive
active
Image by Val Hildreth-Werker
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Byproduct Dissolution
Basalt Dissolution
Hyella stella in limestone
Active Tunneling
Pit Formation
Microcolonial fungi on desert varnish
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Biomineralization
Processes by which organisms form minerals Occurs
in all five major classic kingdoms of life
Ca carbonate shells
Ca oxalate phytoliths
Atacamite worm jaws (Cu2(OH)3Cl)
Lichtenegger et al., 2002. Science 298, 389-392
Silica diatom tests
Apatite bones
Magnetite worm teeth
University of Wisconsin
Nealson et al.
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Microbes are the Best!
Passive active processes
Expert chemists!
Bacteria Archaea Cyanobacteria
1µ
Geobacter metalloreducens
Eukaryotes (plants, animals, fungi)
Geological significance
Extreme environments
10 µ - 100 µ
nucleus
chloroplasts
mitochondia
Hydrothermal vent endodsymbionts
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Biominerals
Sulfates Gypsum Celestite Barite Jarosite Rosyckyi
te
Sulfides Pyrite Hydrotroilite Sphalerite Wurtzite
Galena Greigite Mackinawite
Carbonates Calcite Aragonite Vaterite Monohydrocal
cite Protodolomite Hydrocerussite
Oxalates Earlandite Whewellite Weddelite Glushinsk
ite
Oxides Magnetite Goethite Lepidocrocite Ferrihydri
te Todorokite Birnessite Atacamite Manganite
Phosphates Hydroxylapatite Octacalcium
phosphate Fluorapatite (francolite) Carbonate-hydr
oxylapatite (dahllite) Whitlockite Struvite Brushi
te Vivianite
Fluorides Fluorite Hieratite
A partial and growing list!
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A Microbes View of the Periodic Table
Essential element
Essential element energy source
Micronutrient energy source
Energy source
Toxic (microbes may develop resistance)
Evidence of bioaccumulation (mechanism unclear)
No known use or effect
Graphic by M. Spilde
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Our Hero

• Extremophile bacteria
• Ultra-low nutrient
• Chemical extremes
• Geological agent

• Dissolution
• Precipitation
• Mineral transformation

• Astrobiology!

The Noble Bacterium
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Graphic by M. Spilde
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Why do microorganisms precipitate minerals?
Structure (skeletons, tests or other body parts)
Metabolic waste (e.g. goethite (FeOOH) result of
microbial iron respiration)
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Why do microorganisms precipitate minerals?
To sequester harmful elements U6 is soluble
(toxic), U4 is insoluble. The reduction of U6
to U4 reduces toxicity.
U4O2X
U6 biosorption
Uranium tailings pile Ship Rock, NM
Image by H. Xu, UNM
Uraninite in bacteria
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Why do microorganisms precipitate minerals?
Simultaneous Nutrition and Detoxification!
John Betts
Nealson et al.
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Why do microorganisms precipitate minerals?
To produce natural compasses! Magnetotactic
bacteria deposit magnetic minerals (magnetite
Fe3O4 or greigite Fe3S4) within their cells
Photos by University of Queensland
Single-domain magnets
Magnetite
and Erbium 3 ion, too!
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Why do microorganisms precipitate minerals?
They cant help themselves
Highly charged cell walls
Biofilms (slime layers!)
Even dead microbes can precipitate minerals!
ZnS on biofilm
Image by Banfield et al.
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Biofilms
Ubiquitous
Cold Water Cave Iron Deposits Photo by David
Jagnow
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Mineralogical factories
Photo by Norm Pace
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Biotic or abiotic How can we tell?

• Shapes forms
• Comparison to living counterparts
• Unusual or non-equilibrium minerals
• Isotopic data
• Culturable organisms
• DNA biochemical evidence

Unfortunately, there is no magic bullet!
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Biotic or abiotic How can we tell?

• Shapes forms
• Comparison to living counterparts
• Unusual or non-equilibrium minerals
• Isotopic data
• Culturable organisms
• DNA biochemical evidence

20 um
Dendrites from Spider Cave, Carlsbad Caverns Nat.
Park
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Biotic or abiotic How can we tell?

• Shapes forms
• Comparison to living counterparts
• Unusual or non-equilibrium minerals
• Isotopic data
• Culturable organisms
• DNA biochemical evidence

Modern stromatolites, Australia
Archean stromatolite from western Australia
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Biotic or abiotic How can we tell?

• Shapes forms
• Comparison to living counterparts
• Unusual or non-equilibrium minerals
• Isotopic data
• Culturable organisms
• DNA biochemical evidence

Phylogenetic tree of Archaea from one site in
Lechuguilla
D.E. Northup
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Biotic or abiotic How can we tell?

• Shapes forms
• Comparison to living counterparts
• Unusual or non-equilibrium minerals
• Isotopic data
• Culturable organisms
• DNA biochemical evidence

Vivianite Fe3(PO4)2H2O
Culture after 3 months
Buserite
Culture after 8 months
Birnessite
Switzerite (Mn,Fe)3(PO4)27H2O