The first is a conversation with Nancy Moran, a Yale biologist who studies microbes that become essential to the survival of their hosts. In some cases, these symbionts lose just about all their DNA except for the genes that they use to be useful to their host–leading to the smallest genomes in nature.
The second is a conversation with Susan Golden of UCSD on the subject of time. We humans have a body clock, of course, but so do some bacteria. Why does a microbe need to know the time of day, when its lifespan can be far shorter? That would be like our body clock running a cycle of 1,000 years. Listen to find out.