Bug Fossilization - a geologists perspective
Tomas HodePortland State University
Proving that it was alive..
What to look for when it comes to fossil viruses?
(Analysis – what to analyze, and how?)
Outline
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?
Stuff in rocks
Just to go through the standard things:
Context (my problem, not your problem)- Compatible with life?
Exclusivity - Morphology (possibly)- Chemistry (yes)- Isotopes (?)- Element ratios (?)
What could convince me that it was alive?
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…
We have some problems here…
Example of difficulties
30 μm
Round graphitic features
ErYAG ablation of dental tissue
(Bonus image)
Instant fossilization can give nice preservation, but with time this is changed – cell preservation highly unusual in very ancient rocks.
Modern vs. Ancient preservation
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.
What about viruses in the fossil record?
Exclusivity: - Morphology (small round things..)- Chemistry (virus specific lipids?)- Isotopes (?)- Element ratios (?)
What could convince me that it was a virus?
Context:
What about fossil viruses inside fossil microbes?
What could convince me that it was alive?
Remember – these are the only thing we can analyze:
- Morphology- Elements- Chemistry - Isotopes
Methods/Analysis
Sputtering/etching/tomography
ToF-SIMS mapping of lipids
NMP RBS for C isotopes (D/H ratio?)
What could element ratios tell us?
Methods/Analysis
Ideal case:
Spatial correlation between viro-lipids (at high lateral resolution) and morphological features preserved inside a fossilized microorganism.
Thoughts/conclusion