This is a podcast by the Society for General Microbiology, recorded at a session they sponsored, at the 2010 Times Cheltenham Science Festival. Through genetic manipulation, scientists have created microbes that provide us with medicines, foods and vaccines as well as animals that can be used as model organisms for the study of human disease. The genetic manipulation of organisms and their use is one of the most controversial scientific developments of recent times. Researchers Cormac Gahan, Chris Leaver and Ann Thompson each highlight one practical application of a genetically modified micro-organism that is currently at the research or early development phase. Chaired by Cambridge University's Naked Scientist, Dr Chris Smith, the audience is asked to decide - When is GM acceptable?