He studied Biology at the University of Barcelona (1974) and defended his thesis at the University of Granada). From the beginning of his scientific career he had interest in the diversity and evolution of microbes. He started working with the communities of halophiles that are found in solar salterns along the coasts of Spain and made pioneering contributions describing many new microbes. He started the large school of Spanish halophilologists that has extended over several universities and research centers and where, even today, they continue being among the leaders in the world in this field. From this time comes the largest restructuring of the classification of halophilic Archaea that is still largely accepted. After postdoctoral work at the Universities of Ottawa (Canada) and California, San Francisco he switched to molecular biology still working with halophilic Archaea. He became full professor of Microbiology at the University of Alicante in 1990 and head of the Department of Genetics and Microbiology of this University. There, his work sequencing the genomes of these microbes led one of his students (Prof. Mojica) to sequence for the first time a full CRISPR system that was latter used as model to identify in E. coli the role of such unique prokaryotic system. In the meanwhile, he focused more on the study of marine microbes. During the ‘1990s he pioneered the use of the molecular approach in the study of their biodiversity that was severely limited by the poor cultivability of free-living microbes. In addition, he started to study evolution by analysing the heterogeneity in bacterial gene families, specifically the RNA ribosomal operons. He also participated in the first Spanish oceanographic cruise in which the molecular approach was applied to marine samples, in this case near Antarctica what lead to a publication in Nature. These studies led naturally to his involvement in the first genomes and metagenomes carried out in Spain and in Europe at large. Thus, he was the leader of the first metagenomics study of the Mediterranean published in 2007. With the advent of high throughput sequencing he continued his studies in biodiversity of aquatic environments that have included the Amazon River, the Caspian Sea or Lake Baikal. He has also used genomics and metagenomics to dissect the population genomics of prokaryotic populations. He has described multiple new aquatic microbes in both marine and fresh-water habitats, including Actinobacteria, Verrucomicrobia, Chloroflexi and Cyanobacteria and multiple groups of Archaea (notoriously the marine Talassoarchaea or the hyperhalophile Haloquadratum). He has pioneered also the study of the role of viruses in keeping diversity of populations and mechanisms of evolution. His group is among the leaders in the world in the application of bioinformatics to the study of microbial genomes and metagenomes. They have been pioneers in describing metagenome-assembled genomes (MAGs) that have become an essential tool in the study of the microbial “dark matter”. Bibliometry: a total of 207 peer-reviewed articles. Web of Science H-index 58; Scopus H-index-58; Google Scholar H index 72.