Extracellular proteins limit the dispersal of biogenic nanoparticles
The NanoSIMS 50 is used in this article  to demonstrate the intimate association (yellow and orange areas) of proteins with spheroidal aggregates of biogenic zinc sulfite nanocrystals, an example of extracellular biomineralization. Experiments involving synthetic zinc sulfide nanoparticles and representative amino acids indicated a driving role for cysteine in rapid nanoparticle aggregation. These findings suggest that microbially derived extracellular proteins can limit the dispersal of nanoparticulate metal-bearing phases, such as the mineral products of bioremediation, that may otherwise be transported away from their source by subsurface fluid flow.
C, N (proteins), and S distributions in a TEM section of biofilm:
(A) Composite map of 12C-, 12C14N- for N, and 32S- . Red regions represent relatively pure Sulphur (as ZnS). Orange and Yellow regions indicate the presence of increased levels of Nitrogen in presence of ZnS. Light blue regions indicate the presence of both C and N, with little to no S (no ZnS).
(B) TEM of several conjoined ZnS spheroidal aggregates.
(C) NS50 composite element distribution map of (B).
(D) NS50 composite map of ultra-microtomed Balmat ZnS: no N signal.
(E) NS50 composite map of synthetic nanoparticulate ZnS: no N signal.
The NanoSIMS offers unique capabilities of combining high lateral resolution and benchmark sensitivity for geochemistry applications. It is the only instrument capable of imaging trace elements or isotopic enrichment down to 50nm resolution. Other technologies are limited in sensitivity (TEMS, EELS, EDS, Auger, TOF-SIMS,...) or lateral resolution (conventional SIMS, laser-ICPMS, SEM-EDS, Raman).
 From: John W. Moreau, P.K. Weber, M.C. Martin, B. Gilbert, I.D. Hutcheon, J.F. Banfield, SCIENCE, vol 316, 15 June 2007.