Farell‐Baril, Gerard

The microbiologic nature of self‐replicating, calcifying entity nanoparticles (NPs) isolated from calcified human tissues, including blood vessels and kidney stones is debated because of the difficulty in discriminating minerals precipitated on microbes from minerals nucleated on macromolecules and cell membranes. To begin to resolve this controversy, calcifying bacteria of aquatic origin ( Caulobacter crescentus ) and NPs cultured from human samples were examined using a Scanning Transmission X‐ray Microscope (STXM). The monochromated soft X‐ray beam (150–2000 eV) produced by synchrotron radiation yields microscopic and spectroscopic information on both organic compounds and minerals at the 25 nm scale. High‐spatial and energy resolution Near‐Edge X‐ray Absorption Fine Structure (NEXAFS) spectra indicative of elemental speciation acquired at the C K‐edge and Ca L 2,3 ‐edge on a single‐cell scale from calcified C. crescentus displayed a unique spectral signature different from non‐biologic hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ). Preliminary NEXAFS measurements of calcium and carbon functional groups of cultured NPs revealed organics associated with hydroxyapatite minerals and in one case, spectroscopic signatures similar to those identified in C. crescentus . Using NEXAFS, it is possible to define a biochemical signature of proteins, polysaccharides, nucleic acids, and hydroxyapatite for cultured calcified bacteria suggesting that NPs isolated from human samples share spectroscopic characteristics with calcifying bacteria.