Population dynamics, interactions and evolution of marine microbes using genomic approaches

• Main Author: Latorre Pérez, Francisco
• Other Authors: Universitat Politècnica de Catalunya. Departament d'Enginyeria Civil i Ambiental, Logares Haurie, Ramiro Ernesto, Jaillon, Olivier, Mösso Aranda, César
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universitat Politècnica de Catalunya 2023
• Subjects: Population dynamics; Evolution; Interactions; Marine microbes; Protists; High-throughput sequencing; Single-cell Genomics; Marine ecology; Metagenomics; Marine environment; Sola; North Atlantic
• Online Access: http://hdl.handle.net/2117/396974; http://hdl.handle.net/10803/689381; https://doi.org/10.5821/dissertation-2117-396974

A la portada: Institut de Ciències del Mar (English) There is a myriad of microorganisms on Earth contributing to global biogeochemical cycles. In the surface ocean, the smallest microbes (picoplankton) are responsible for an important fraction of the total atmospheric carbon and nitrogen fixation. The ocean picoplankton encompasses both prokaryotes (bacteria and archaea) and tiny unicellular eukaryotes (protists). Despite their overall importance for the functioning of the biosphere, many questions remain unanswered on their biogeography, population dynamics, interactions, and evolution. Answering these questions is essential in the context of global change, as alterations of the ocean microbiome could impact the function of multiple ecosystems. In this thesis, we aim at reducing the knowledge gap on the above topics through the application of High-Throughput Sequencing (HTS) and genomic approaches, using data collected during the circumglobal Tara Oceans and Malaspina-2010 expeditions, as well as at the Gulf of Maine (North Atlantic), and two Northwestern Mediterranean coastal microbial observatories (BBMO and SOLA stations). Chapters 1 and 2 are dedicated to a small protistan group of heterotrophic flagellates (HF): the Marine Stramenopiles (MAST)-4, relevant during picoplankton grazing and nutrient remineralization. Due to its widespread distribution and relatively high abundance, MAST-4 has become a target group of microbes to study HF. Unfortunately, MAST-4 remains uncultured. We investigated four evolutionary-related species of MAST-4 (species A, B, C, and E) by reconstructing their genomes with Single-Cell genomics data. In chapter 1, co-occurrence and biogeographic analyses in the surface global ocean indicated contrasting patterns driven by temperature. Although MAST-4 species were similar in terms of broad metabolic functions, they differed in the set of genes related to the food degradation machinery. We proposed that differential niche adaptation to temperature and prey type has promoted the ...