Bug Fossilization a geologists perspective

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Bug Fossilization - a geologists perspective

• Tomas Hode
• Portland State University

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Outline

• Proving that it was alive..
• What to look for when it comes to fossil viruses?
• (Analysis what to analyze, and how?)

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Stuff in rocks

• Ok I see a lot of things in my rocks.
• Round things, elongated things, rod-shaped
  things, carbonaceous things, isotopically
  depleted things, etc., so what is required to
  convince me that it was alive?

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What could convince me that it was alive?

• Just to go through the standard things
• Context (my problem, not your problem)
• - Compatible with life?
• Exclusivity
• - Morphology (possibly)
• - Chemistry (yes)
• - Isotopes (?)
• - Element ratios (?)

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We have some problems here

• 1. Fossilization can preserve morphology, but if
  non-specific it is of little help.
• 2. Organic molecules lose functional groups
  lipid backbones preserved if we are lucky.
  Isotopes not really a help unless extreme
  fractionation or certain context.
• 3. Discrepancy between recently fossilized
  material and ancient rocks

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Example of difficulties
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Round graphitic features
30 µm
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(Bonus image)
ErYAG ablation of dental tissue
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Modern vs. Ancient preservation

• Instant fossilization can give nice preservation,
  but with time this is changed cell preservation
  highly unusual in very ancient rocks.

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What about viruses in the fossil record?

• Ok, we have a problem here the mechanisms of
  preservation gives you only rudimentary
  information in the rock record.
• Preserved morphology is of no help when it comes
  to viruses unless it can be correlated with e.g.
  chemistry.

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What could convince me that it was a virus?

• Exclusivity
• - Morphology (small round things..)
• - Chemistry (virus specific lipids?)
• - Isotopes (?)
• - Element ratios (?)

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What could convince me that it was alive?

• Context
• What about fossil viruses inside fossil microbes?

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Methods/Analysis

• Remember these are the only thing we can
  analyze
• - Morphology
• - Elements
• - Chemistry
• - Isotopes

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Methods/Analysis

• Sputtering/etching/tomography
• ToF-SIMS mapping of lipids
• NMP RBS for C isotopes (D/H ratio?)
• What could element ratios tell us?

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Thoughts/conclusion

• Ideal case
• Spatial correlation between viro-lipids (at high
  lateral resolution) and morphological features
  preserved inside a fossilized microorganism.