The present invention relates to the field of nanotechnology, more specifically to the manufacture or treatment of nanostructures, and in particular provides arsenic sulfide nanostructures, as well as a process for obtaining nanostructures of arsenic sulfide.The present invention provides a process for obtaining arsenic sulfide (As—S) nanostructures from a microorganism, which comprises the steps of culturing under appropriate conditions the strain Fusibacter ascotence in the presence of a source of sulfur and a source of arsenic; and recovering arsenic sulfide nanostructures (As—S) from the precipitate obtained from said culture.The present invention provides, also, a nanostructure of arsenic sulfide which is a nanowire having a monoclinic crystal structure. The present invention further provides a nanostructure of arsenic sulfide, which is a nanoparticle with a monoclinic crystal structure.