Bug Fossilization a geologists perspective Tomas Hode Portland

Bug Fossilization - a geologists perspective Tomas Hode Portland State University

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

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?

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 (? )

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…

Example of difficulties

Round graphitic features 30 μm

(Bonus image) Er. YAG ablation of dental tissue

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

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.

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

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

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

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

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