Acinetobacter baumannii Transcriptome under blue light or in the dark. Acinetobacter baumannii ATCC 19606 = CIP 70.34 = JCM 6841 isolate:ATCC 19606

Light sensing in chemothrophic bacteria has been relatively recently ascertained. In the human pathogen Acinetobacter baumannii, light is able to modulate key aspects contributing to its success as a pathogen such as motility, biofilm formation and virulence in a way that depends on the BLUF photoreceptor BlsA. In addition, light can induce reduction in susceptibility to certain antibiotics such as minocycline and tigecycline in a photoreceptor-independent manner, directly inducing expression of resistance genes. In this work, we have identified new traits modulated by light in this pathogen, which comprise not only important determinants related to pathogenicity/resistance, but also to the bacteria´s survival in the environment. For example, we show that the phenylacetic acid catabolic and the trehalose biosynthesis pathways, which have been related to virulence in A. baumannii and Xanthomonas citri, respectively, are modulated by light, and these responses completely depend on BlsA. Furthermore, BlsA adjusts catalase expression in response to blue light. In addition, other important genes such as those coding for the type VI secretion system, an efflux pump and a novel cluster of genes likely involved in lipid modification were found to be differentially induced by light. Overall, our results indicate that light perception in A. baumannii appears as a generalized aspect of its lifestyle and could have profound influences in its success as a pathogen.