MICROBIOLOGY: A Bacterial Pathogen Sees the Light

Light, a nearly ubiquitous environmental signal, regulates myriad developmental and behavioral responses in plant, fungal, bacterial, and animal cells. Photosensitive proteins abound in the bacterial kingdom, but their cellular functions often remain a mystery. On page 1090 in this issue, Swartz et al. (1) identify a functional role for a new type of light sensor in bacteria--light, oxygen, or voltage (LOV) histidine kinase. In the notorious pathogen Brucella abortus, light increases the enzymatic activity of this kinase, which, remarkably, increases virulence of the bacterium. Related LOV histidine kinases are conserved across a range of bacterial taxa, suggesting that this virulence pathway could be one of many new photosensory pathways regulating bacterial physiology.