Iron oxides from Modern to Archean – nm-scale balls... nannobacteria or not?

Folk, Robert L.
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Among many hundreds of SEMs of iron oxides taken over many years and from a great many localities, certain similarities stand out. When studied at 50,000x or more, they are seen to consist of small balls in the 30-150 nm range, previously identified in carbonates, clay minerals, etc. as cells of dwarf bacteria (nannobacteria). In Fe oxide samples, are these small balls also nannobacterial cells or are they just the way that IN-organic Fe oxide precipitates? A simple trick helps to answer this question: iron oxides dissolve when hit with HCl (at different rates depending upon which iron oxide mineral is involved), but organic cells will resist solution (see Folk and Carlin, 2006). In this survey from modern, living iron bacteria to rocks from Greenland over 3 billion years old, interesting similarities are revealed. Nanocells of the same size are present the whole way through. If these tiny cells are not nannobacteria, then someone needs to come up with a viable alternative.