A green-fluorescent siderophore protects bacterial communities from UV damage

Abstract

Sunlight enables virtually all life on earth, but also entails harmful ultraviolet (UV) radiation inducing DNA damage. In response to UV stress, natural selection has favored both curative and preventive measures such as DNA repair mechanisms and UV-absorbing pigments. While UV protection by pigments is well documented in plants, animals and fungi, little is known about their protective role in bacteria. Here, we combine batch-culture and microscopy experiments to show that the siderophore pyoverdine, a fluorescent pigment produced by the opportunistic pathogen Pseudomonas aeruginosa offers high-level protection against UV radiation. Our results reveal that bacteria up-regulate pyoverdine production following UV exposure, seemingly as part of a general stress response. We further found that pyoverdine cannot curatively alleviate UV-damage but protects cells preventively and collectively from oncoming UV exposures through its accumulation in the environment. Altogether, our results reveal a new and non-canonical function of this iron-scavenging molecule, demonstrating that pyoverdine acts as a public sunscreen protecting bacterial populations from UV damage. Given that many bacteria produce pigments, such protection might be widespread in species colonizing habitats exposed to UV radiation.