A culture of a single bacterial taxon. On solid media, this is seen as the presence of a single colony type. A pure culture cannot be ascertained if different taxa display similar colony morphologies on solid media. Likewise, a pure culture cannot be ascertained in liquid media. In both cases, the only proof of a pure culture is your prior knowledge that the media has been inoculated with a single colony. On a primary isolation media, a pure culture is not necessarily composed of a single clone. In order to obtain a single clone, one colony must be subcultured on new media to obtain an ‘isolate’.