The present invention reports the conductive properties of Geobacter sulfurreducens pili (geopili) and their use in nanotechnology applications. More specifically the present invention provides methods for culturing cells of G. sulfurreducens to produce conductive pili, as well as methods for their isolation and for their modification in order to produce biological nanowires or biological/inorganic hybrid devices with different functionalities. The invention provides applications for cells expressing native or modified pili as well as for the isolated native or modified pili.