Actually, Methuselah would be a snot-nosed kid compared to this chain of
bacterial cells. The image above is of a short chain of fossil
cyanobacterial cells that were extracted from Bitter Springs chert of
northern Australia. They are an estimated 1 billion years old. It may
seem shocking that bacteria and other microbes can leave fossil footprints,
but bacteria are actually record holders with entries in the fossil record
book at estimated ages of 3.5 billion years. But some microbes, like
cyanobacteria and other members of the "blue-green algae" family, have
relatively thick cell walls, and can form stromatolites, thick mats of
bacterial filaments, that can be sliced open to reveal exquisitely
preserved fossil bacteria. Cyanobacteria (there are still relations alive
and well today) are aquatic and photosynthetic. The oxygen atmosphere that
we depend on was generated by numerous cyanobacteria during the Archaean
and Proterozoic Era.
This image came from the University of California Museum of Paleontology, a
great site with lots of information on fossils, some of which are bigger
than bacteria.
