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Understanding Fossilization of Microbes and Viruses: Insights from Geology

This presentation by Tomas Hode from Portland State University explores the complex processes of fossilization, particularly regarding ancient organisms such as microbes and viruses. It discusses key aspects that geologists consider when determining if a specimen was once alive, including morphology, chemistry, and isotopic analysis. Hode emphasizes the challenges in fossilizing viral entities and the importance of contextual evidence in proving their existence. By analyzing preservation mechanisms and certain characteristics, this work aims to provide a clearer understanding of how we can identify life in the geological record.

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Understanding Fossilization of Microbes and Viruses: Insights from Geology

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Presentation Transcript

  1. Bug Fossilization - a geologists perspective Tomas Hode Portland State University

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

  3. 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?

  4. 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 (?)

  5. 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…

  6. Example of difficulties

  7. Round graphitic features 30 μm

  8. (Bonus image) ErYAG ablation of dental tissue

  9. Modern vs. Ancient preservation Instant fossilization can give nice preservation, but with time this is changed – cell preservation highly unusual in very ancient rocks.

  10. 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.

  11. What could convince me that it was a virus? Exclusivity: - Morphology (small round things..) - Chemistry (virus specific lipids?) - Isotopes (?) - Element ratios (?)

  12. What could convince me that it was alive? Context: What about fossil viruses inside fossil microbes?

  13. Methods/Analysis Remember – these are the only thing we can analyze: - Morphology - Elements - Chemistry - Isotopes

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

  15. Thoughts/conclusion Ideal case: Spatial correlation between viro-lipids (at high lateral resolution) and morphological features preserved inside a fossilized microorganism.

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