Light Modulates Metabolic Pathways and Other Novel Physiological Traits in the Human Pathogen Acinetobacter baumannii

TUTTOBENE, MARISEL R.; MÜLLER, GABRIELA L.; ALTILIO, MATÍAS; AMEZAGA, MAITENA MARTÍNEZ; NGUYEN, MEAGHAN; RAMÍREZ, MARÍA SOLEDAD; MUSSI, MARÍA ALEJANDRA

New Orleans

Congreso; ASM Microbe 2017 - American Society for Microbiology; 2017

ASM Microbe

Light sensing, which was until recently considered to be restricted to phototrophs, has been relatively recently ascertained to occur also in chemothrophs. Acinetobacter baumannii is a threatening human pathogen whose outstanding capability to acquire resistance to multiple drugs, as well as its ability to persist in the hospital environment are key aspects contributing to its success as a pathogen. We have previously shown that motility, biofilm formation and virulence against C. albicans are modulated by light in this microorganism, and depend on the BLUF photoreceptor BlsA. In addition, light can reduce the susceptibility to certain antibiotics such as minocycline and tigecycline in a photoreceptor-independent manner, by a mechanism that likely involves induction of expression of specific resistance genes. In this work, we have identified other novel bacterial physiological processes modulated by light, revealed by a whole transcriptome approach followed by genetics, physiological and biochemical validation. In fact, we present evidence indicating that light influences bacterial metabolism, which represents quite a novel concept for chemotropic bacteria. Indeed, we found that the phenylacetic acid catabolic pathway as well as the trehalose biosynthesis are repressed and induced by light, respectively, responses that completely depend on BlsA. Also, catalase levels were found to be finely adjusted in response to blue light by BlsA, probably to counteract the production of reactive oxygen species by light. We further present evidence indicating that tolerance to fluoroquinolones, which could contribute to persistence in the hospital environment, as well as surfactant production are modulated by light. Finally, the expression of other gene clusters involving not only important determinants related to pathogenicity but also to resistance such as the whole type VI secretion system and Emr-type efflux pumps, were found to be differentially induced by light. Overall, our results indicate that light appears as a stimulus modulating global features of A. baumannii lifestyle, and could have profound influences in its success as a pathogen.