This doctoral thesis, supervised by Manuel Porcar, Cristina Vilanova and Juli Peretó, compares the different microbiota isolated from solar panels from different locations, explores the antioxidant properties of some of their bacteria and describes Sphingomonas solaris, a new species isolated from a solar panel in Boston. The results of the thesis have been published in the journals Frontiers in Microbiology, Environmental Microbiology Reports, International Journal of Systematic and Evolutionary Microbiology and Microbial Biotechnology. The thesis was defended on February 15, 2021.

The main objective of the thesis "Life under the sun: microbial ecology and applications of the solar panel microbiota" was bioprospecting the microbiota of photovoltaic solar panels. The thesis followed two main lines: the study of the ecology of the microbial communities and the potential applications of the anti-stress activities present. Firstly, the taxonomic and functional diversity of solar panels located in different geographical locations: València, Boston and Berkeley (at approximately the same latitude) and solar panels located in Antarctica and within the Arctic Circle were compared. A remarkable similarity in the microbiological composition of the solar panels was observed, regardless of their location. A study of the microbial colonisation of the solar panels over a two-year period and the effect that these communities could have on the efficiency of the photovoltaic panels was also carried out. The plates start to be colonised by generalist bacteria and, later, extreme conditions (high irradiation, desiccation, large thermal oscillations) select a community enriched in microorganisms adapted to these conditions. No significant influence of biofilms on photovoltaic efficiency was found. On the other hand, most of the bacteria present in these communities produce abundant carotenoids. The anti-stress effects of these bacteria were explored using a bioassay on the nematode Caenorhabditis elegans and some strains with a remarkable effect on the model organism on its longevity, resistance to oxidation and protection against ultraviolet light were described. Solar panels may be a source of new micro-organisms of industrial interest. This research led to the description of a new bacterial species, Sphingomonas solaris, isolated from a solar panel at the Arnold Arboretum in Boston.

Kristie Tanner's doctoral thesis was carried out at the biotechnology company Darwin Bioprospecting Excellence, located at the University of Valencia Science Park, in collaboration with the Biotechnology and Synthetic Biology group of I2SysBio under the supervision of Manuel Porcar (Researcher at the University of Valencia), Juli Peretó (Professor of Biochemistry and Molecular Biology at the University of Valencia) and Cristina Vilanova (Scientific Director of Darwin). During the development of the thesis, Kristie Tanner has been the beneficiary of a contract from the Industrial Doctorate programme of the MiCInn and carried out a research stay at Harvard University with a grant from the Real Colegio Complutense. The examining board was formed by José Luis García (CSIC), Trent Northen (Joint Genome Institute, Berkeley National Lab, California) and María Lluch (CRG and Pulmiobiotics SL), who graded the thesis as outstanding.