Virus Fossils

James Laidler

History of Prokaryotic Fossils

• Walcott 1915 - Pre-Cambrian cyanobacteria (~ 600 - 700 Mya)

• Tyler and Barghoorn 1954 - Pre-Cambrian cyanobacteria (~ 1.9 Gya)

• Schopf and Packer 1987 Early Archaean (3.3 - 3.5 Gya)

• Oldest rocks - 3.85 Gya• Earth cool enough for liquid water - ~4 Gya

Schopf JW (2006) Fossil evidence of Archaean life.Phil. Trans. R. Soc. B. 361:869-885

Schopf JW (2006) Fossil evidence of Archaean life.Phil. Trans. R. Soc. B. 361:869-885

History of Viral Fossils

• • • • • •

Can Viruses Fossilize?

• Viruses used as templates– Metalization– Mineralization– Form recognizable tubes– Carbon from virus detectable by EDXS

• No environmental examples…yet

Silicate Reactions

• Polymerization occurs at neutral pH and higher

• Bind strongly to amine groups at low pH - enhanced by proton pump activity– Al and Fe accelerate the process– Other metals (Pb, Cd, Cr, Cu, Zn) also accelerate

the process

R - PO3 - OH + Si(OH)4 = R - PO3 - O - SiO2 - OH + H2O

R - COOH + Si(OH)4 = R - CO - O - Si(OH)3 + H2O

R - CH2 - OH + Si(OH)4 = R - CH2 - O - Si(OH)3 + H2O

Phosphate residues

Carboxyl residues

Alcohol residues

Silicate Reactions with Organic Matter

Experimental Plan:Benchside

• Incubate TMV and SIRV in neutral silicate solution

• Incubate TMV and SIRV in acidic silicate solution in presence of Fe and/or other metals

• Examine for silicified virus particles by TEM• Imbed and section specimens and examine

with EDXS for carbon signature

Why TMV and SIRV?

• Both TMV and SIRV are uniform in size and shape (TMV is used as a size standard)

• Simple shapes (cylinders) not seen in nature • TMV is widely used for a template in

nanotechnology• SIRV is found in acidic hot springs• No good candidate (yet!) for neutral hot

springs (most are head-tail phages)

SIRV1

830nm23nm

TMV

18nm 300-310nm

Experimental Plan:Fieldwork

• Collect silicate sinter at high-silica, low pH hot springs (e.g. BSL)

• Collect silicate sinter at high-silica, neutral pH hot springs (e.g. MHS/GHS)

• Examine under TEM for formations suggestive of viruses

• Section and examine for carbon and phosphorus signature by EDXS

• Publish the world’s oldest known viral fossils