Virus Fossils

1
Virus Fossils

• James Laidler

2
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

3
Schopf JW (2006) Fossil evidence of Archaean
life. Phil. Trans. R. Soc. B. 361869-885
4
Schopf JW (2006) Fossil evidence of Archaean
life. Phil. Trans. R. Soc. B. 361869-885
5
History of Viral Fossils

6
Can Viruses Fossilize?

• Viruses used as templates
• Metalization
• Mineralization
• Form recognizable tubes
• Carbon from virus detectable by EDXS
• No environmental examplesyet

7
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

8
Silicate Reactions with Organic Matter
Phosphate residues
R - PO3 - OH Si(OH)4 R - PO3 - O - SiO2 -
OH H2O
Carboxyl residues
R - COOH Si(OH)4 R - CO - O - Si(OH)3
H2O
Alcohol residues
R - CH2 - OH Si(OH)4 R - CH2 - O -
Si(OH)3 H2O
9
Experimental PlanBenchside

• 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

10
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)

11
23nm
830nm
SIRV1
12
18nm
300-310nm
TMV
13
(No Transcript)
14
Experimental PlanFieldwork

• 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 worlds oldest known viral fossils

15
(No Transcript)