CONICET | Buscador de Institutos y Recursos Humanos

In our group we have found that many bacterial pathogens such as Acinetobacter baumannii sense and respond to light integrating also a temperature signal. We have extensively characterized photoregulation at moderate temperatures such as 24ºC in this microorganism, showing that light exerts a global effect on its physiology modulating aspects related to persistence in the environment as well as virulence. We have shown that many of these processes depend on the blue light using FAD (BLUF) photoreceptor BlsA, which is a global regulator able to bind and antagonize the functioning of transcriptional regulators such as Fur in a light-dependent manner. Regulation by light occurs not only in A. baumannii, but is also widely distributed within the Acinetobacter genus. Most non-baumannii species harbor between two and six BlsA homologs, and photoregulation occurs not only at 24 but also at 37ºC. Many of these species are environmental, while others like Acinetobacter A47 and nosocomialis are important human pathogens. A. nosocomialis harbors three BLUF photoreceptors while A47 harbors two, modulating susceptibility to antibiotics, motility, iron uptake and hemolysis in the last case. Regulation by light at 37ºC in important pathogens could affect bacterial infections in humans. This situation could be particularly relevant for these pathogens given that they produce infections in skin wounds surface-exposed and soft tissue.In this work, we evaluate the effect of light in infections by A47, A. nosocomialis and A. baumannii towards a human keratinocyte cell line in culture, HaCaT. The model resembles skin wound infections, in which the stratum corneum has lost integrity and the bacteria come in direct contact with the cells. In this context, this model reflects situations in real infections, given that these species of Acinetobacter are recognized as natural colonizers of human skin. In this work, we have optimized infections using this model, varying the multiplicity of infection (MOI), time for adhesion or internalization, as well as antibiotic treatment. Our results so far show that light exerts an effect on A. nosocomialis virulence towards HaCaT cells, becoming the bacteria more virulent when in the dark rather than under blue light. In non-baumannii species, some processes such as biofilm formation, iron uptake or motility are regulated by light inversely than in A. baumannii, and in this work we show that virulence is also affected. Our results also pose the possibility that light could be regarded as a tool to control infections by these microorganisms.