Resumen de Life under the sun: microbial ecology and applications of the solar panel microbiota
The prokaryotic world is vast and diverse, and a large fraction of it still remains to be explored. Microbial diversity is everything except random: microorganisms are the result of evolution and adaptation. This diversity provides us with an incredible arsenal of unique and useful tools that can be used in a wide range of industrial and pharmaceutical applications. The search of these biological tools is what we know as bioprospecting and, taking into account that only a fraction of the global microbial diversity has been explored to date, the number of – yet to be discovered – strains, genetic tools or metabolites with biotechnological or biomedical applications is overwhelming. This opens a great market opportunity for the biotechnology industry and, particularly, for microbiology‐based commercial developments. Many bioprospecting efforts have focused on well‐known environments such as soil, a rich source of antibiotic-producing microorganisms and bacteria with insecticidal properties; or human gut, from which probiotic bacteria such as Lactobacillus spp. can be isolated. Nevertheless, many unusual environments remain poorly or unexplored to date although they are certainly valuable sources of novel products. We consider an unusual environment as one that is both poorly explored, taxonomically distant from the human‐associated microbiome and that is under extremophilic conditions. In this work we have focused on a particularly extreme unusual environment: solar panel surfaces. These smooth glass or glass-like surfaces have minimal water retention capacity and maximum sunlight exposure. Solar panels can be found practically all over the world, and can be used as standard devices to study microbial communities and their colonization process in different geographical locations. Furthermore, solar panel surfaces are not only exposed to desiccation and high irradiation, but also to frequent temperature fluctuations, making them ideal sources of stress-resistant microorganisms. The work performed in the present thesis aimed to further explore the solar panel microbiota from both an ecological and an applied perspective. On one hand, the microbial communities inhabiting solar panels from different geographical locations have been analyzed in taxonomic and functional terms, and the colonization process of these surfaces has been studied in depth using a miniaturized solar farm. On the other hand, microbial strains have been isolated from this environment and further analyzed to determine biological activities of interest and to characterize and describe novel microbial species. Our results suggest that, despite the physical distance, solar panel surfaces from around the world display microbiomes with taxonomic and functional similarities. In particular, the genera Hymenobacter, Sphingomonas, Streptomyces, Pseudomonas, Bradyrhizobium, Methylobacterium, Modestobacter and Deinococcus constitute the core of the solar panel microbiota. Furthermore, the microbial communities inhabiting solar panel surfaces display several stress-resistance mechanisms (i.e. stress response, capsule development, metabolite repair heat shock chaperone proteins, genes for carotenoid biosynthesis, superoxide dismutases, peroxidases and compatible solutes) and, in the colonization process of solar panel surfaces, there is a transition from an initial generalistic community, to a final specialized community composed of highly resistant bacterial and fungal genera. Finally, solar panel surfaces can be sources of new microbial species and of carotenoid-producing microorganisms with powerful antioxidant properties.
