27. Earth Bacteria--E. coli
For comparison with the possible martian microfossils (slide #26), this slide shows an electron microscope view of a common Earth bacterium, prepared the same way as the possible martian microfossils. The many rods and sausage shapes here are individual cells of the bacterium Escherichia coli, or E. coli for short. The view in this slide is 9.5 micrometers across, so each E. coli bacterium is about 1–2 micrometers long and about 0.25 micrometer in diameter. The E. coli are the same shape as the possible fossils in slide #26, but are 10 to 100 times as big. This difference in size translates to a huge difference in volume — the possible martian microfossils have only one thousandth to one millionth of the volume of E. coli cells.
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