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Extracellular production of tellurium nanoparticles by the photosynthetic bacterium Rhodobacter capsulatus

“…The biosyn-thesis of TeNPs ouside the cells is likely to involve two steps: (i) the reduction of tellurite to elemental Te 0 mediated by the redox solu-ble carrier, lawsone, and (ii) the subsequent growth of Te 0 crystals into TeNPs possibly via the Ostwald ripening mechanism [32,34]. Reduction of tellurite to elemental Te 0 can be carried out intracellularly, in the periplasmic space or extracellularly in different microorganisms and thus, the growth of bacterial TeNPs can take place either inside or outside the cell cytosol [3][4][5][6][7][8][9]21]. It should be noted that the present study did not distinguish between TeNPs that grew outside the cells by means of the redox mediator law-sone from those which grew into cytosol and then were released in the growth medium by cell lysis (see graphical abstract).…”

“…Exogenous Te • deposits are particularly evident in those species, such as Sulfurospirillum barnesii and Bacillus bev-eridgei, able to use tellurite and tellurate as exogenous electron acceptors under anaerobic respiration conditions [4]. However, also other species such as Pseudomonas aeruginosa, E. coli, Erwinia carotovora and Agrobacterium tumefaciens accumulate Te 0 deposits in the periplasmic space, that is, outside the cytoplasm [8].…”