The contrast between light and dark is a powerful metaphor in art and literature, and this contrast is no less relevant to the field of microbiology. As well as being an energy source, light is a very important signal that can provide valuable information about an organism's position within a niche and its environment. On page 713, Herrou and Crosson describe recent advances in our understanding of how bacteria sense blue photons through the flavin-binding photosensors known as LOV domain proteins. They discuss insights into the mechanisms by which light can regulate the activity of LOV proteins, and how these proteins may be useful for protein-engineering applications.
Turning to a darker place, we now realize that the diversity and prevalence of life on the ocean floor and in the oceanic crust is far greater than we had originally imagined. On page 703, Edwards and colleagues describe the recent advances that have been made in understanding the diversity of microbial populations in this environment, and discuss the technological advances that have allowed us to sample the sea floor at depths of around 4 km below the ocean surface and even within the igneous crust itself.
