Explain why the organisms that were studied by Sergei Winogradsky could not be grown on Robert Koch’s plate media containing agar or gelatin. Solution The organisms studied by Sergei Winogradsky are lithotrophs. Lithotrophs are the organisms that need inorganic nutrients to synthesise the biomolecules necessary for the survival. Robert Koch’s plate media containing agar or gelatin provides only organic nutrients. So, the lithotrophs studied by Sergei Winogradsky could not be grown on Robert Koch’s plate media..