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• W2029643195 abstract "Nicolau van Uden was born in Venlo (The Netherlands) in 1921 and he studied in Vienna University where he got his degree in medicine (Fig. 1). A few years later, he married Marie Adelaide de Bragança, a member of the Portuguese royal family. This was determinant for his establishment in Portugal, where he lived for more than 40 years. During his first years in Portugal, van Uden worked as an invited researcher in a small laboratory in the Faculty of Sciences of the University of Lisbon. When he was already a recognized yeast specialist, he was invited to participate in the design of a Centre of Biology, integrated in the Gulbenkian Institute of Science that the Gulbenkian Foundation was building in Oeiras, in the gardens of the Marquis of Pombal palace. When the Centre was finished, van Uden was appointed as director of the Laboratory of Microbiology, which he had designed in every detail, and he worked there for the rest of his life. In 1969, he became the first director of the Teaching Department of the Gulbenkian Institute of Science and created and launched the “Estudos Avançados de Oeiras” (Advanced Studies of Oeiras). This programme of international monographic courses had a multidisciplinary approach and brought to Portugal during the summer months hundreds of students from the whole world, attracted by the quality of the speakers and the excellence of the practical laboratory work. Nicolau van Uden (1921–1991). In the early seventies, he was invited to pursue an academic career and he did it completing all the traditional Portuguese academic requirements. He got a doctorate in Biology in the University of Coimbra, the oldest of Portugal, in 1974. Then he got the highest academic title of “agregado” in Microbiology in the New University of Lisbon and finally he was appointed as the first Full Professor of Microbiology in the Faculty of Sciences and Technology of this University. As an output-oriented legacy of his research, a yeast culture collection, of over 2000 strains, representing around 450 species, was established, this constitutes the current “Portuguese Yeast Culture Collection–PYCC” integrated in a European network of microbial databases and culture collections. Along his life he edited one book, wrote 21 reviews and book chapters, and published 121 research articles. He belonged to the editorial board of several journals, including “Yeast,” and his work was also recognized with a doctorate “honoris causa” in the Orange Free State University (South Africa) and with honorary membership of several learned societies. He represented Portugal in councils and panels of NATO, EU, European Federation of Biotechnology, International Union of Microbiological Societies and the Academies of Sciences of the USA. He died in 1991, and the following lines are an attempt to summarize his main achievements and to evaluate their relevance in the framework of the biology of his time and in that of modern biology. Nicolau van Uden began his research, as a medical student, in a clinical laboratory of Dermatology in Vienna. His first published articles were about syphilis and human and animal pathogens like Aspergillus, Histoplasma and Microsporum. Then, after moving to Portugal, he shifted his research interests to pathogenic yeasts. This country and these microorganisms were to be his home and the objective of his work until his death. In 1956, he published the first report on the detection of the pathogenic yeast Candida albicans in vegetables (1). In the same year, he also published another article on the fungal aetiology of a veterinary problem, the mycotic abortion in cattle (2). The distribution of Candida albicans and Cryptococcus neoformans was also a focus of his interests, but soon he moved from pathogenesis to ecology. In the following years, he described and analysed the intestinal yeast-microbiota of many domestic animals (cattle, horses, sheeps, goats and swine) (3) and also those from wild animals such as hippopotami, wart hogs, bush pigs (4) and baboons (5) in samples collected during his travels to Mozambique. During this period of yeast “hunting” in nature, his interests extended to free-living yeasts of lakes and sea, prompted largely by a visit to the Scripps Oceanographic Institute at La Jolla in California where he stayed with Dr. J. W. Fell. Several new species were identified and described from surveys carried out in the Atlantic and other oceans. His publications on these organisms (6-8) continue to be a reference in the field. It is noteworthy that such studies were not merely descriptive, but rather intended to disclose the rules that governed yeast distribution and to contribute to a general model of yeast ecology. According to van Uden's way of foreseeing the future, the overall achievements besides their intrinsic importance, served to build up the conceptual framework for his subsequent research. This was a multidisciplinary approach, based on an extended sample of yeast biodiversity, in which the tools of taxonomy, ecology and physiology were all used with the same scientific accuracy. It was the ability to synergistically promote this joined evaluation that allowed van Uden to visualize such new concepts on yeast biology, which would turn into System Biology. An important example was the seminal work on the relation between temperature and yeast growth and death described by van Uden in the late fifties (9) and theoretically elaborated some years later (10). These studies, which assumed high relevance in his scientific career, originated outstanding contributions for the field of thermo-microbiology. A representative piece of his work will be discussed hereafter. In the late sixties van Uden moved, with a small team of collaborators and even smaller equipment resources he had collected in previous years, to the laboratories he had designed in the Biology building of the Gulbenkian Institute of Science (Fig. 2). There he found the optimal physical environment (space and equipment) and the nutrients (financial support) that he needed to grow, as microorganisms do under these conditions, at a maximum specific rate. There was no lag time, because his mind was already prepared to take full advantage of these optimal conditions. He knew what had to be done and he did it quickly. In 1969, he created the Advanced Studies of Oeiras, financed by the Gulbenkian Foundation, and in the same year, he invited Dr. Luis J.P. Archer, who had just returned from USA with a PhD in bacterial genetics, to teach a course on bacterial transformation, which was the introduction of Molecular Biology in Portugal. Those summer courses were an excellent culture medium to develop van Uden's ideas on human resources development, postgraduate teaching in modern biology and to inoculate interest in yeast into Portuguese and also Spanish scientific communities. In the same summer, the students could learn a broad range of areas, for example, mitochondrial biochemistry with Dr. Angelo Azzi, Dr. Ernesto Carafoli, Dr. Martin Klingenberg and, especially, Dr. Jeff Schatz; thermodynamics of biological processes with Dr. Henry Albert Bent; and Biometry with Dr. Robert Sokal and Dr. James Rholf, to mention just some names of a long list of excellent specialists in their fields, coming from Europe and USA to give these intensive courses to 20–25 selected students during 3–4 weeks. The students had also access to a computer that, in those early seventies, was a “monster” occupying a big refrigerated room and which worked with heaps of punched cards. These courses represented in postgraduate teaching the van Uden's own multidisciplinary approach to biological research. A great proportion of professors, who presently chair departments of Biochemistry and Molecular Biology or Microbiology in Spanish and Portuguese universities, spent some summers in Oeiras in the seventies and eighties. The laboratories also benefited from recruiting PhD students attracted by a stimulating scientific environment created by researchers with diverse fields of interest. Overall, not only the students but also the laboratories benefited from it because the material resources and the equipment available were extraordinary for that time in the Iberian Peninsula. Van Uden Microbiology Laboratory members and staff, Gulbenkian Institute of Science, 1990. Nicolau van Uden was deeply persuaded of the usefulness of mathematical equations and modelling in biology, a field currently close to systems biology that is getting special attention nowadays. He considered mathematical modelling, not only as the most rigorous way to describe the microbial behaviour, but also, and mainly, as an excellent tool to analyse it and to discover new ways to advance the knowledge of their underlying mechanisms. For these reasons and in spite of being painfully conscious of his limited knowledge on mathematics, he devoted much time and work to develop mathematical descriptions of yeast behaviour. Taking advantage of his scientific background and previous work, he channelled his studies to three main interrelated fields: (i) the kinetics of thermal death at supraoptimal temperatures, (ii) the kinetics and energetics of yeast growth and (iii) the ethanol effects on the kinetics of death, growth and fermentation. In the field of the kinetics of thermal death he described quantitatively, for the first time, the occurrence of simultaneous growth and death in yeasts cultured at supraoptimal temperatures. These experiments demonstrated the heterogeneity of yeast populations, in which, under certain circumstances, some cells were growing and others dying, something completely unexpected, as microbial populations were considered to be homogenous. Loyal to his mainstream idea that a better knowledge could be obtained with a multidisciplinary approach, he used many species instead of a single one for thermo-microbiological studies. With such approach, he was able to describe different relations of thermal death and exponential growth, which corresponded to two distinct death processes among yeasts species (11). In this line, he observed that most yeasts generally growing at higher temperatures, showed a temperature range (e.g., 36–44°C, for Saccharomycescerevisiae) where thermal death and growth concurred, and designated them as associatively profiled yeasts. In a few other yeasts, the temperature range of thermal death was well separated (some 3 up to 10°C) from the temperature range at which exponential growth took place: the dissociatively profiled yeasts. Moreover, with these studies, he found out that antimicrobial agents were able to affect these profiles, either by transforming associatively profiled yeasts into dissociative or by moving the whole profile “en bloc”. Remarkably, he found out that thermally produced respiratory-deficient yeasts were detected only in associatively profiled yeasts and raised the hypothesis that mitochondria contained the structures (e.g., DNA, inner membrane) targeted by thermal stress (12). In relation to the kinetics and energetics of yeast growth, by using the chemostat and competitive inhibitors of glucose transport that did not affect the intracellular metabolism like sorbose, van Uden was able to show that growth rate of fermenting yeast was limited by the transport rate of glucose (13). A decade later, metabolic control theory confirmed this, by showing the transport step as having the highest control coefficient of all the enzymes participating in yeast glycolysis. Conscious of the importance of the transport step, he stimulated his students to study the transport kinetic of several substrates (e.g., sugars, organic acids, ammonia; 14) and some new proton symports (e.g. for fructose, lactate; 15) were subsequently discovered in Saccharomyces and other yeast genera. The kinetic quantitative data on the temperature profiles and the studies on the effects of ethanol on the kinetics and energetics of yeast growth enabled him to reinforce mitochondria as the target of thermal death (16). He also devoted extensive studies to the theory of chemostat (17) and promoted its use in many laboratories at the time. In the end of the seventies and early eighties, van Uden followed his interest in exploiting yeast activity for biotechnology purposes: starch utilization and ethanol tolerance. The analysis of the yeast biodiversity to convert raw materials (utilization of starch as sole carbon and energy source) to produce added value products such as single cell protein was also pursued. It was in this context, that temperature profile of growth, death and biomass yield using starch were described. He characterized the extracellular amylolytic system, subjected to carbon catabolite repression and attempted derepression by UV mutagenesis (18). The research on ethanol tolerance in fermentation yeasts, particularly of S. cerevisiae, occupied him during his last years. In a coherent approach to the problem of ethanol toxicity and its biotechnological impact, he begun by studying its effects on the other two processes he had studied before, the thermal death and the nutrient transport through the plasma membrane. He was able, by simple (but not simplistic) physiological approaches, to identify the plasma membrane and mitochondria as the main targets of the ethanol toxicity in yeast, gaining a comprehensive picture of these complex phenomena. The resulting data were published in several international journals being in the forefront of the scientific advances on physiological and biochemical basis of the process, further confirmed and explored in the Molecular Era. His expertise in this field was also recognized by the publication of several reviews (19, 20), and the invitation to edit a book on Alcohol Toxicity (21). Understanding ethanol toxicity in yeast is still a challenge due to the growing worldwide interest for production of alcoholic beverages and of ethanol from renewable fuel sources, where the van Uden's models are still up to date. With the current knowledge on the interrelation between mitochondria and yeast programmed cell death, van Uden's results deserve new attention. In addition, his findings that a single stress agent, like acetic acid, was able to induce two types of thermodynamically different cell deaths (low and high enthalpy death; 22), should be revised under the light of the current knowledge on the multiple physiological ways of dying, from apoptosis to necrosis. Revisiting his models and approaches is, now more than ever, essential to tackle the new and emergent challenges in the understanding of cellular and molecular response of yeast, a powerful model system in higher eukaryotic cell biology, to stressors. Mathematical modelling of yeast processes did not only result in deep satisfactions, as when an underlying mechanism was unravelled or when a model was validated, but also brought some disappointments. In 1999, Dr. F.C. Neidhart wrote a guest commentary for the Journal of Bacteriology (vol. 181; 24), entitled “Constant obsession with dN/dt”. In that article, even before describing “the mathematical elegance and simplicity, but more important, its invitation to explore” of the growth equation, he remarked the following: “One of life's inevitable disappointments … come from expecting others to share the particularities of one's own sense of awe and wonder”. Van Uden developed a similar obsession with dN/dt and mathematical modelling in general. Like Dr. Neidhart, he also felt, first the beauty and scientific importance of the mathematical description of yeast behaviour, and then the disappointment of verifying that his enthusiasm was shared or understood by only a few of his yeast colleagues. One of these few was Dr. Anthony Rose, who hosted, in the first edition of “The Yeasts”, a chapter by van Uden reviewing his recent results and models on yeast growth kinetics (23). Dr. Rose wrote later in van Uden's obituary in “Yeast” that his “approach … to develop mathematical predictions of microbial behaviour … left most yeasts physiologists gasping”. Perhaps the conceptual framework of the seventies was not a good one to receive fruitfully his models, although he tried hard to disseminate them by all means including publication in journals with high impact, as Annual Review of Microbiology (24). Now, 40 years later, the scientific landscape has strongly changed. The development and use of mathematical models, whose parametric values are the result of hundreds of reactions connected systemically, is at the core of Systems Biology. This new background will likely provide new opportunities to appreciate the actual relevance of van Uden models and ideas about yeast kinetics and energetics. Nicolau van Uden was known as Nico by his many friends; for his disciples, even when they were already professors, he was always “o doutor”, the doctor. On the day of his 70th birthday, he would have to retire and leave the laboratories he created, where he had worked intensely every day for more than 20 years. Perhaps he could not imagine how to live out of his laboratory. The passing away of the “doutor” was a shock for friends and disciples. His work was followed by his disciples scattered among several universities in Portugal and Spain. The meetings “Jornadas de Biologia de Leveduras Prof. Nicolau van Uden”, organized by the Portuguese Society of Microbiology are a well-deserved tribute to his dedication to yeasts, their biochemistry and ecology. Professor Nicolau van Uden's creative thinking and the seminal work he developed were the inoculum of a growing “yeast scientific community” that fermented and are still respiring the knowledge produced by the unique soul of Nico van Uden. The authors would like to express their gratitude to all their colleagues who worked with Nicolau van Uden and also to his many friends around the world. A special acknowledgement is due to Carlos Gancedo (Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM. Madrid)." @default.
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• W2029643195 title "Nicolau van Uden, a life with yeasts (1921-1991)" @default.
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