A silicon cell cycle in a bacterial model of calcium phosphate mineralogenesis.

Abstract The prokaryote Corynebacterium matruchotii produces calcium phosphate (bone salt) and may serve as a convenient model for examining individual factors relevant to vertebrate calcification. A factor of current clinical uncertainty is silicon. To investigate its possible role in biomineralisation advanced optical (digital deconvolution and 3D fluorescent image rendering) and electron microscopy (EDX microanalysis and elemental mapping) were applied to calcifying microbial colonies grown in graded Si concentrations (0–60 mM). Cell viability was confirmed throughout by TO-PRO-3-iodide and SYTO-9 nucleic acid staining. It was observed that calcium accumulated in dense intracellular microspherical objects ( type s i–iii ) as nanoparticles (5 nm, type i ), nanospheres (30–50 nm, type ii) and filamentous clusters (0.1–0.5 μm, type iii), with a regular transitory Si content evident. With bacterial colony development (7–28 days) the P content increased from 5 to 60%, while Si was displaced from 60 to 5%, distinguishing the phenomenon from random contamination, and with a significant relationship ( p