From genes to microbial consortia: multi-level bioprospecting of natural and artificial environments

Microbial bioprospecting is the identification of microorganisms, genes, enzymes, and/or metabolic pathways with biotechnological applications in industry or in research itself. This thesis aimed at bioprospecting a range of unexplored, natural and artificial environments subjected to harsh physicochemical conditions by applying a multi-level strategy. The microbial communities were analyzed in a first step by means of metagenomic sequencing, which yielded an extensive catalog of the microbial species and/or genes occurring in the community, and allowed the ecological contextualization of new habitats. Culturing in artificial media was used as a complementary approach in order to isolate, select, and characterize microbial strains of particular relevance. Last, a bioinformatics algorithm was developed in order to visualize community assemblage based on the predicted associations and interactions shaping microbial consortia in environmental samples. As a result of our analysis, a range of individual microbial strains, genes and microbial consortia with potential biotechnological applications have been identified. Moreover, we propose a new, holistic approach for the efficient mining and analysis of environmental microbiomes

Towards a Microbial Thermoelectric Cell

Microbial growth is an exothermic process. Biotechnological industries produce large amounts of heat, usually considered an undesirable by-product. In this work, we report the construction and characterization of the first microbial thermoelectric cell (MTC), in which the metabolic heat produced by a thermally insulated microbial culture is partially converted into electricity through a thermoelectric device optimized for low ΔT values. A temperature of 41°C and net electric voltage of around 250–600 mV was achieved with 1.7 L baker’s yeast culture. This is the first time microbial metabolic energy has been converted into electricity with an ad hoc thermoelectric device. These results might contribute towards developing a novel strategy to harvest excess heat in the biotechnology industry, in processes such as ethanol fermentation, auto thermal aerobic digestion (ATAD) or bioremediation, which could be coupled with MTCs in a single unit to produce electricity as a valuable by-product of the primary biotechnological product. Additionally, we propose that small portable MTCs could be conceived and inoculated with suitable thermophilic of hyperthermophilic starter cultures and used for powering small electric devices

Extremophilic microbial communities on photovoltaic panel surfaces: a two-year study

Solar panel surfaces can be colonized by microorganisms adapted to desiccation, temperature fluctuations and solar radiation. Although the taxonomic and functional composition of these communities has been studied, the microbial colonization process remains unclear. In the present work, we have monitored this microbial colonization process during 24 months by performing weekly measurements of the photovoltaic efficiency, carrying out 16S rRNA gene high-throughput sequencing, and studying the effect of antimicrobial compounds on the composition of the microbial biocenosis. This is the first time a long-term study of the colonization process of solar panels has been performed, and our results reveal that species richness and biodiversity exhibit seasonal fluctuations and that there is a trend towards an increase or decrease of specialist (solar panel-adapted) and generalist taxa, respectively. On the former, extremophilic bacterial genera Deinococcus, Hymenobacter and Roseomonas and fungal Neocatenulostroma, Symmetrospora and Sporobolomyces tended to dominate the biocenosis; whereas Lactobacillus sp or Stemphyllium exhibited a decreasing trend. This profile was deeply altered by washing the panels with chemical agents (Virkon), but this did not lead to an increase of the solar panels efficiency. Our results show that solar panels are extreme environments that force the selection of a particular microbial community