Análisis descriptivo y funcional de las colonias microbianas visibles que crecen en la cueva de Altamira, enfocado al diseño de medidas de control

Abstract

The main objective of this Thesis work was the study and characterization of the visible microbial colonies that grow on the walls and ceilings of the Altamira cave, which constitute the main threat of biodeterioration for the paintings in this cave. With this objective, we have used massive sequencing techniques (amplicon and shotgun) that allowed us to identify a core of 36 OTUs that represent the components most frequently found within the different types of visible colonies in Altamira. In this core, some very predominant components stood out (one or two per colony) which we have called major components (CMs) and which were characteristic in each colony. These CMs, which by the amplicon technique turned out to be three, were classified within the phylum Actinobacteria with the family Euzebyaceae (OTU1) and the genus Crossiella (OTUs 2 and 4). Their uneven distribution in the colonies has been the basis for differentiating the Gray and White colonies into 2 subtypes, indicating that the classification by color is not enough to describe the diversity of the colonies. With the shotgun technique we have recovered 90 genome drafts (MAGs), being between 6 and 34 MAGs, the number of final components that were recovered per colony. The taxonomic assignment of the CMs suggested that these CMS represent unknown candidate taxa in the phylum Actinobacteria. From the comparative analysis carried out of between the different types of visible colonies, we have been able to propose a general pattern of colony composition applicable to the Altamira visible colonies and probably to any similar biofilm formed in caves. In addition, we have predicted the metabolic and physiological functions present in the metagenomes of the visible colonies, which suggests that in addition to a heterotrophic lifestyle based on preformed organic compounds, the colonies could grow in an autotrophic way under low availability of organic matter. Finally, the good quality drafts of the predominant components in the colonies allowed the development of specific primers against these components, and with them, of PCR assays that detect the presence of before-mentioned components. These detection tests represent a substantial improvement in the methods of microbiological monitoring of the biodeterioration of caves and other cultural assets. Likewise, the genomic information provided in this thesis can be the basis for designing effective control measures to combat eventual problems of biodeterioration caused by visible colonies.