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Currently, global energy requirements rely heavily on fossil fuels, the primary contributors to global warming and severe climate changes. It is imperative to decarbonize the energy supply sector, by utilizing an alternative, clean and sustainable energy source, like hydrogen, that can be generated from renewable resources, such as solar energy. The aim of this dissertation was the construction of a new biophotocatalytic system using non-photosynthetic anaerobic bacteria coupled with semiconductor metal sulfide nanoparticles, for light-driven H2 production. In this system, nanoparticles act as light-harvesting material, enabling the microorganism to capture and absorb sunlight energy, using it for H2 generation. In the present work, four bacteria Citrobacter freundii , Clos tridium acetobutylicum , Desulfovibrio vulgaris and Desulfovibrio desulfuricans were used as biocatalysts with self-produced cadmium sulfide (CdS) nanoparticles to produce hydrogen. The performance of these biohybrids was further compared with the control system Escherichia coli -CdS. Moreover, new semiconductor combinations were tested, by loading cocatalysts metals tungsten (W), nickel (Ni) and molybdenum (Mo) into CdS. The D. desulfuricans -CdS biohybrid was demonstrated to be the best photocatalytic system for light-driven H2 production from the four biohybrids proposed and E. coli -CdS control system. D. desulfuricans -CdS system presented a remarkable H2 production both in the presence and absence of the electron mediator methyl viologen (MV), with 46.0±4.8 and 31.7±8.1 µmol of H2, respectively, after 45 and 142 h of light irradiation. The D. desulfuricans -CdS performance was improved by adding cocatalysts, especially Mo, that allowed the increase of H2 production rate from 34.0±0.8 to 130.8±9.3 µmol gdcw-1h-1, without MV. Finally, D. desulfuricans -CdS-MoS2 was successfully immobilized in calcium alginate beads and a batch photoreactor for H2 production was constructed. These results show the high potential of D. desulfuricans -CdS-MoS2 biohybrid photosystem for an efficient and clean hydrogen production.

RESUMEN Introducción: Los líquenes son asociaciones simbióticas mutualistas entre un hongo y una o más algas verdes o cianobacterias. Actualmente se han reportado interacciones entre los líquenes y bacterias no fotosintéticas, sin embargo, no se conoce a detalle cómo ocurren, y la diversidad y potencial de esta relación aún no han sido explorados completamente. Con el uso de nuevas herramientas moleculares y nuevos métodos de cultivo, fueron detallándose las funciones de las bacterias no fotosintéticas relacionadas con los líquenes y, por lo tanto, fue posible analizar su asociación simbiótica. Por ello, esta investigación tiene como objetivo analizar la diversidad de bacterias no fotosintéticas y los procesos metabólicos de éstas que permiten la supervivencia de los líquenes. Metodología: A partir de la búsqueda y análisis de trabajos recientes (2015-2020) se obtuvo información sobre los filos de bacterias no fotosintéticas presentes en líquenes y se analizaron los procesos metabólicos de estas bacterias en relación con la supervivencia de los líquenes en los que se encontraban. Resultados: Los filos bacterianos frecuentemente encontrados en líquenes son Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes Verrucomicrobia, Chloroflexi, Acidobacteria y Thermus. Discusión: Estos grupos de bacterias llevan a cabo procesos como la fijación de nitrógeno, producción de hormonas, pigmentos y vitaminas que contribuyen con la nutrición, protección y regulación del crecimiento del liquen. Conclusión: Los líquenes pueden considerarse como un micro-ecosistema que cuenta con interacciones simbióticas mutualistas entre varios organismos y su estudio es importante ya que permite comprender con mayor profundidad su importancia ecológica. ABSTRACT Introduction: Lichens are mutualistic symbiotic associations between a fungus and one or more green algae or cyanobacteria. Interactions between lichens and non-photosynthetic bacteria have currently been reported, however, it is not known in detail how they occur, and the diversity and potential of this relationship have not yet been fully explored. With the use of new molecular tools and new culture methods, the functions of non-photosynthetic bacteria related to lichens were detailed and, therefore, it was possible to analyze their symbiotic association. Therefore, this research aims to analyze the diversity of non-photosynthetic bacteria and their metabolic processes that allow the survival of lichens. Methodology: From the search and analysis of recent works (2015-2020), the phyla of non-photosynthetic bacteria present in lichens were obtained and the metabolic processes of these bacteria were analyzed in relation to the survival of the lichens in which they were found. Results: The bacterial phyla frequently found in lichens are Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes Verrucomicrobia, Chloroflexi, Acidobacteria y Thermus, Discussion: These groups of bacteria carry out processes such as nitrogen fixation, production of hormones, pigments and vitamins that contribute to the nutrition, protection and regulation of the growth of the lichen. Conclusion: Lichens can be considered as a micro-ecosystem that has mutualistic symbiotic interactions between various organisms and their study is important since it allows us to understand their ecological importance in greater depth., {"references":["Asplund, J., & Wardle, D. A. How lichens impact on terrestrial community and ecosystem properties. Biological Reviews 2017; 92(3): 1720-1738.","Cernava, T., Berg, G., & Grube, M. High life expectancy of bacteria on lichens. Microbial ecology 2016; 72 (3): 510-513.","Sigurbjörnsdóttir, M. A., Andresson, O.S., & Villhelmsson, O. Analysis of the Peltigera membranacea metagenome indicates that lichen-associated bacteria are involved in phospate solubilization. Microbiology 2015; 161(5): 989-996.","Aschenbrenner, I.A., Cernava, T., Berg, G., & Grube, M. Understanding microbial multi-species symbioses. Frontiers in Microbiology 2016; 7: 180.","Grube, M., Cernava, T., Soh, J., Fuchs, S., Aschenbrenner, I., Lassek, C., et al. Exploring functional contexts of symbiotic sustain within lichen-associated bacteria by comparative omics. The ISME journal 2015; 9(2): 412-424.","Leiva, D., Clavero-León, C., Carú, M., & Orlando, J. Intrinsic factors of Peltigera lichens influence the structure of the associated soil bacterial microbiota. FEMS microbiology ecology 2016; 92(11).","Cernava, T., Müller, H., Aschenbrenner, I.A., Grube, M., & Berg, G. Analyzing the antagonistic potential of the lichen microbiome against pathogens by bridging metagenomic with culture studies. Frontiers in microbiology: 2015; 6:620.","Hodkinson, B. P., & Lutzoni, F. A microbiotic survey of lichen-associated bacteria reveals a new lineage from the Rhizobiales. Symbiosis 2009: 49(3): 163-180.","Cardinale, M., Puglia, A. M., & Grube, M. Molecular analysis of lichen-associated bacterial communities. FEMS Microbiology Ecology 2006; 57(3): 484-495.","Biosca EG, Flores R, Santander RD, Díez-Gil JL & Barreno E. Innovative Approaches Using Lichen Enriched Media to Improve Isolation and Culturability of Lichen Associated Bacteria. PLos ONE 2016; 11(8).","Sierra, M.A., Danko, D.C., Sandoval, T.A., Pishchany, G., Moncada, B., Kolter, R., et al. The microbiomes of seven lichen genera reveal host specificity, a reduced core community and potential as source of antimicrobials. Frontiers in microbiology 2020; 11: 398.","Sigurbjörnsdóttir, M. A., & Vilhelmsson, O. Selective isolation of potentially phosphate-mobilizing, biosurfactant-producing and biodegradative bacteria associated with a sub-Arctic, terricolous lichen, Peltigera membranacea. FEMS microbiology ecology; 2016; 92(6).","Parrot, D., Antony-Babu, S., Intertaglia, L., Grube, M., Tomasi, S., & Suzuki, M. T. Littoral lichens as a novel source of potentially bioactive Actinobacteria. Scientific Reports 2015; 5: 15839.","Garg, N., Zeng, Y., Edlund, A., Melnik, A. V., Sánchez, L. M., Mohimani, H., et al. Spatial molecular architecture of the microbial community of a peltigera lichen. Msystems: 2016, 1(6).","Erlacher, A., Cernava, T., Cardinale, M., Soh, J., Sensen, C. W., Grube, M., et al. Rhizobiales as functional and endosymbiontic members in the lichen symbiosis of Lobaria pulmonaria L. Frontiers in microbiology 2015; 6: 53.","Cernava, T., Erlacher, A., Aschenbrenner, I. A., Krug, L., Lassek, C., Riedel, K. et al. Deciphering functional diversification within the lichen microbiota by meta-omics. Microbiome: 2017; 5(1): 1-13.","Cernava, T., Vasfiu, Q., Erlacher, A., Aschenbrenner, I.A., Francesconi, K., Grube, M., et al. Adaptations of lichen microbiota functioning under persistent exposure to arsenic contamination. Frontiers in microbiology 2018; 9: 2959","West, N. J., Parrot, D., Fayet, C., Grube, M., Tomasi, S., & Suzuki, M. T. Marine cyanolichens from different littoral zones are associated with distinct bacterial communities. PeerJ 2018; 6.","Kim B, Han SR, Lamichhane J, Park H & Oh TJ. Draft Genome Analysis of Antimicrobial Streptomyces Isolated from Himalayan Lichen. J. Microbiol Biotechnol: 2019; 29: 1144-54.","Spribille, T., Tagirdzhanova, G., Goyette, S., Tuovinen, V., Case, R., & Zandberg, W. F. 3D biofilms: in search of the polysaccharides holding together lichen symbioses. FEMS Microbiology Letters 2020; 367(5).","Hawksworth, D. L., & Grube, M. Lichens redefined as complex ecosystems. New Phytologist 2020; 227 (5), 1281."]}