Enrique Cerdá‐Olmedo: An Outstanding Scientist and Mentor

Last December, Professor Enrique Cerdá-Olmedo, one of the most brilliant and innovative figures in Spanish Genetics, passed away. Enrique, as he always wanted to be called, dedicated his life to the study of genetic mechanisms in microorganisms, becoming not only an international reference in fungal genetics, but also a pioneer of molecular genetics in Spain and an exceptional teacher for several generations of biologists. His work contributed significantly to establishing modern genetics in his country, leaving a legacy that transcends his numerous scientific discoveries. As a researcher, he stood out for his extraordinary experimental rigour and uncommon creativity. An original thinker, his work ranges from contributions to genetic mechanisms in bacteria and fungi to the evolution of secondary metabolism and behaviour in microorganisms. In his extensive teaching and research career, he trained several generations of scientists, to whom he conveyed his enthusiasm for science. He always demanded experimental rigour and was known for his scientific creativity. In addition, his institutional commitment and his vocation for the dissemination of scientific knowledge deeply influenced those that worked with him. Born in Guadix (Granada, Spain) in 1942, Enrique grew up in a historical context marked by a post-civil war period, a time of enormous material limitations. From an early age, he showed an enormous capacity for learning and a tendency towards rigorous study and academic excellence, which would be reflected in his winning the Extraordinary High School Award and, later, the National Graduation Award. His first university education was as an agricultural engineer at what was then the Higher Technical School of Agricultural Engineers in Madrid, now part of the Polytechnic University of Madrid, where he also obtained a PhD degree. His initial training focused on applied aspects of plant physiology and genetics, which had a lasting impact on his research objectives, since he always had an interest in basic genetic mechanisms but also on their applications. A decisive factor in Enrique's intellectual development was his early interactions with leading scientific figures. Among his first teachers was Enrique Sánchez-Monge, a prominent Spanish plant breeder who taught him how basic genetics could combine with breeding applications. However, learning the details of plant breeding was not enough for Enrique's thirst for knowledge, and he enrolled in a degree in Biological Sciences from the Complutense University of Madrid. This dual foundation in agricultural engineering and biology provided him with a broad perspective that would facilitate his subsequent research career. After graduating from Madrid, Enrique continued his training with a PhD in California as a graduate student at Stanford University, in the laboratory of Philip C. Hanawalt, co-discoverer of DNA repair. His work with Hanawalt focused on mutation, replication, and repair in Escherichia coli, and introduced him to the new field of molecular biology that led to his PhD in Biology in 1967. After graduation, Enrique moved to the California Institute of Technology (CalTech) in Pasadena, as a postdoctoral researcher under the supervision of Nobel laureate Max Delbrück, a leading figure in early molecular biology research. This postdoctoral period lasted between 1967 and 1969. Delbrück's personality, characterized by his extraordinary intellectual acuity and critical thinking, had a profound influence on Enrique's understanding of science and resulted in the rigour and theoretical and experimental audacity he displayed throughout the rest of his career. During this period, he began his work with his preferred research model, the fungus Phycomyces blakesleeanus, chosen by Max Delbrück for its responses to external stimuli, such as light. Later, Enrique returned to CalTech as a Fairchild Distinguished Scholar (1974–1975) and continued his collaboration with Max Delbrück and his group until his death in 1981. His formative years in the United States and his frequent trips for short stays in CalTech allowed the integration of Enrique in the group of scientists that redefined modern genetics and molecular biology. In 1969, he joined the University of Seville in Spain with the support of the distinguished biochemist Manuel Losada Villasante. He was hired to organize the teaching and research of Genetics as part of a new degree in Biology, and he became the first Professor of Genetics at the University of Seville in 1972 until his retirement in 2012. He also made a decisive contribution to the newly created Faculty of Biology, of which his department was a part, actively participating in the design of the new centre and its syllabus. The founding of the Department of Genetics was not a mere administrative act, but the deliberate creation of a research and teaching centre inspired by the most demanding international standards, with which he became familiar in the United States. Enrique always valued mobility and interaction with other research centres, and he facilitated the incorporation of new researchers from other universities who went on to create their own research groups. This hallmark has been one of the distinguishing features of the Department, which currently has more than 40 lecturers spread across three different research centres (https://departamento.us.es/dgenetica/Genetica/Main.html). In its 56 years of existence, its members have published hundreds of articles (around 500 in the last 15 years, according to its website) and presented more than 200 doctoral theses, 33 of which were supervised by Enrique himself. Over time, many of his former PhD students became full professors of Genetics at different Spanish academic centres and abroad. The formation of a new generation of researchers contributed decisively to the institutional consolidation of microbial genetics in Spain. From October 2012, Enrique became Professor Emeritus at the University of Seville for 3 years, a recognition that crowned four decades of teaching and research activity. Throughout his career, Enrique investigated different features of the biology of bacteria and fungi, selecting organisms that could serve as models for addressing fundamental questions. In bacteria, he used E. coli to investigate the mechanisms of mutation and DNA repair, as well as aspects of toxicogenetics. However, it is in the study of fungi that his contribution reaches greater originality and depth. He researched extensively using species from genera such as Phycomyces, Blakeslea, Fusarium and Saccharomyces, using them as experimental systems to explore sexual and asexual genetic mechanisms, responses to light and other external stimuli, and secondary metabolism, with an emphasis on carotenoid production. Another key aspect of his scientific legacy is the development of experimental methods that were incorporated as innovative contributions to the practice of fungal genetics. His studies of mutagenesis and quantitative analysis of heterokaryons enabled him to develop procedures that facilitated the genetic analysis of coenocytic fungi, expanding the experimental possibilities in the field. These methods reflect a constant theme in his career: the combination of conceptual creativity with technical rigour, and a concern for leaving useful tools for the scientific community beyond specific results. Enrique's research on secondary metabolism is another of his major contributions. Among his most notable achievements, in the 1970s he discovered an enzyme complex responsible for carotene synthesis in Phycomyces and described its genetic regulation, opening a new avenue for understanding the coordinated biosynthesis of these metabolites. Other notable contributions included the demonstration of compartmentalization in terpenoid biosynthesis, the development of a method for obtaining mutants in gibberellin synthesis, which were little known at the time due to the difficulty of identifying them, and his studies on the regulation of the production of these compounds. Many of these works had applications and led to various patents, such as the identification of improved conditions to produce gibberellin GA1, which is of biotechnological interest and was put into practice by an Andalusian company. His contributions to the production of carotene in Blakeslea were also noteworthy, with clear biotechnological implications due to the use of this organism for industrial-scale production. His research group also made major contributions to the characterization of the metabolism of apocarotenoids in Phycomyces and their role as sexual signals in this fungus and other related species. Among the most notable milestones in his career are his contributions to the sensory physiology of fungi using Phycomyces as a model. The fruiting body of this fungus moves in response to light, gravity, wind and the presence of nearby objects. In 1973, Enrique's group combined genetic analysis of sensory mutants with their phenotypic characterization to propose the first genetic signalling pathway in a fungus: an ordered scheme of gene products that mediate between receptors and effectors in Phycomyces. Enrique published 94 primary scientific papers, 63 reviews and book chapters, and numerous articles in other contexts, as well as 10 patents. He is the author of ‘Nuestros genes’ (Salvat) and four other books, and the director and main author of ‘Phycomyces’ (Cold Spring Harbor Laboratory Press). He also translated two scientific books and directed the film ‘Life of Yeasts’, produced by the Institut für den Wissenschaftlichen Film (Germany), with versions in Spanish, German and English, a notable example of the integration of science, education and audiovisual media. His international activities included stays as a Humboldt Fellow at the University of Göttingen (1982–1983), Visiting Scientist at the Fondazione Cenci-Bolognetti in Rome (2005–2006), and additional visits to eight institutions in five countries, as well as numerous short stays. He directed courses at Cold Spring Harbor Laboratory (USA) and other institutions in five countries and gave lectures and seminars in 18 countries. He was an elected member of the Royal Academy of Engineering of Spain, the European Molecular Biology Organization (EMBO), and the Royal Seville Academy of Sciences. His numerous Spanish awards include the King Jaime I Prize for Scientific Research, the Medal of Andalusia, the National Genetics Prize and the Javier Benjumea and Manuel Aguilar prizes. Enrique was an exceptional teacher, and his classes left a deep impression on his students. He was innovative in his methods and modernized the teaching of genetics at the University of Seville. He was convinced that students would better understand genetic analysis if he first explained the molecular basis of inheritance. He then changed the teaching programme so that it started with the ‘molecular genetics’, section followed by sections on genetic analysis and population genetics. His classes in the Molecular Genetics course, which he taught in the fourth year of the Biology degree, captivated students with their clarity, his first-hand knowledge of many of the authors of the experiments he described, and the deductive method he used to help them understand the basic principles of the subject. When continuous assessment was still a little-used concept at his university, the Molecular Genetics course that Enrique designed was divided into seven parts, each with its own exams and problem sets. The course was complemented by practicals, writing assignments and seminars given by the students, which allowed them to accumulate merits towards their final grade. Enrique's most innovative contribution to teaching, however, was the Molecular Biology course, in which students were introduced to research by conducting experiments supervised by some of the department's doctoral students. To participate in this course, students should previously earn a good grade in Molecular Genetics, in addition to performing well in the previous course in General Genetics. Due to its practical nature—the course was fully experimental—and against official regulations in Biology teaching around that time, only 12 students were admitted each year. The twelve chosen were divided into four groups that rotated periodically in their composition and in the ongoing research project, in whose election the students also participated. The classes, which began at an unusual time to reduce problems with public transportation, consisted of discussing the results obtained and proposing new experiments. This subject attracted several generations of biologists to research and cemented Enrique's prestige as a trainer of researchers in molecular biology. Enrique with Mariquilla González in his home at Sevilla in 2025. Javier Avalos: writing – original draft, writing – review and editing. Luis M. Corrochano: writing – original draft, writing – review and editing. The authors have nothing to report. The authors declare no conflicts of interest. The authors have nothing to report.