NANOMETER-SCALE FEATURES OF SEDIMENTARY PHOSPHATE: NANNOBACTERIAL, METAZOAN OR INORGANIC PRECIPITATION?

Collaboration with Mayo Clinic medical researchers has shown that hardening and blockage of human arteries is done by H-apatite precipitated by culturable nannobacteria-like organisms (Folk et al., 2001 GSA abs.; V. Miller et al., 2004 AmJPhys-Heart). These form minute spheroids, typically 25-80 nm, which precipitate bony material where it does not belong. This finding inspired a project to look at dinosaur bones, to see if there might be “good” (as well as “evil”) nannobacteria symbiotically precipitating apatitic bone. These bones, if not diagenetically altered, do indeed consist of similar-sized spheroids, in the 25-70 nm range. Spheroids of 20-40 nm also occur in mammoth and deer bones (work with K. O'Heim, J. Rodgers, T. Rowe). Human tooth enamel also consists of 45-250 nm spheroids, either as unorganized masses or as chains.

Moving on to non-skeletal phosphates, phosphatic sands and nodules contain normal size bacteria (<1 ìm) as well as an abundance of 100 – 400 nm spheroids. Diagenetic precipitation of phosphates in pore spaces produced nearly euhedral 1-2 micron hexagonal crystals of phosphate (cf. Hubert et al. '96 JSedR.) that may represent small overgrowths on bacterial bodies.

A radical view would suggest that, since spheroids of the same general size range and appearance are found in all of these situations, and human arterial plaque is the result of nannobacterial precipitation of phosphate, then calcium phosphates in the whole spectrum of occurrences may be precipitated by the same organisms. A conservative view would say that these amazing resemblances are just a coincidence, that purely inorganic nucleation or metazoan cellular processes produce features that only superficially look like the nannobacterial precipitates in human arteries.