FIGURE 8.

Analytical spectroscopy of biogenic tungsten deposits in the cells of M. sedula after 21 days of cultivation with W-POM. (A) High-resolution TEM (HR-TEM) image of S-layer fragment of M. sedula cell. (B) HR-TEM and Fast Fourier Transform (FFT) acquired from the tungsten crystalline cell surface deposits labeled in panel (A). (C) HR-TEM image of the intracellular part of M. sedula cell; inlet represents magnified labeled area showing that intracellular nanoparticle is surrounded by electron dense layer which may suggest the presence of membrane; (D) HR-TEM and FFT obtained from intracellular nanoparticle labeled in panel (C). Insets in panel (B,D) represent diffraction patterns consistent with the tungsten carbide WC and W₂C phases. (E) Comparison of Energy Los Near Edge Spectra (ELNES) recorded from W-M4,5 edge with the reference spectra from a WC phase (pink line) and simulations of W-containing phases of W-POM (brown line) and of the areas depicted in Figure 5F (black and green lines).