Dr Chris Smith and the Naked Scientists with science news stories and analysis. In today’s programme: Scientists discover the world’s biggest bacterium, evidence that we pick our friends based on how they smell, and do brain training apps really work?

Plus... we tackle a thorny issue - if we rely too heavily on solar and wind power, and the sun doesn’t shine and the wind doesn’t blow where the demand is, how do we keep the lights on? Dr Chris Smith and the Naked Scientist team present the latest science news, analysis and breakthroughs.