Upload
salene
View
26
Download
0
Tags:
Embed Size (px)
DESCRIPTION
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 - PowerPoint PPT Presentation
Citation preview
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