Mycology O Zaragoza, Instituto de Salud Carlos III, Madrid, Spain r 2017 Elsevier Inc. All rights reserved.
Mycology is the discipline of biology that describes and studies a very vast group of organisms denominated fungi. This group contains around 90,000 species, and thousands are described every year, being estimated that there might be more than one million fungal species in the world, which makes the fungal kingdom one of the most important in the tree of life. Fungi are very variable, because they include both macroscopic (such as mushrooms, trufﬂes and puffballs) and microscopic organisms. All of them share some common characteristics. They are non-motile heterotrophic eukaryotes that possess a cell wall around the cell, which differs from the cell wall of plants because it contains different components (mainly chitin). Most fungi can reproduce by both sexual and asexual reproduction. Although we are not aware of it, fungi have a great impact in our daily habits, and our society and way of living would be very different in the absence of these organisms. Fungi are widely found in the environment, and they have multiple beneﬁcial effects and applications. But these organisms are also the cause of devastating plagues and diseases, so their control is mandatory in agriculture and biomedicine. In this article, I will provide a brief overview of the impact of fungi in our life.
The “Good” Mycology: Fungi as Dr. Jekyll Fungi are key organisms in multiple processes that can be described with adjectives such as “productive” or “beneﬁcial,” and this applies to areas such as agriculture, biotechnology and environmental biology. Many different types of mushrooms have become delicious ingredients in multiple recipes (some of them very expensive and fancy!), so there is an important industry dedicated to the cultivation of these organisms. But other fungi, such as yeasts or molds, are important biotechnological tools, since they are required for the production of daily consumed products, such as alcoholic drinks (beer, wine), cheese, bread, cakes and others. Furthermore, fungi are an important source of metabolites with antimicrobial properties. It is well known that the ﬁrst antibiotic was isolated from the mold Penicillium, and nowadays there is a long list of medicines, pigments and other compounds that are produced by fungi. In this context, fungi such as Yarrowia lipolytica or Pichia pastoris, are excellent models to express and purify vaccines, hormones and other compounds of biotechnological interest. Fungi also play an important role in the maintenance of ecological systems. A large number of fungi participate in the transformation and recycling of dead material (animals and plants) to the soil, so they it can be used as nutrient sources again. Many fungi are also saprophytes or commensals, and they are capable of establishing interactions with other organisms. For example, fungi are required for the growth of many plants because they form symbiotic associations with the roots (called mycorrhizae), which provide a source of nutrients (mainly sugars and minerals) to the plant. Many microscopic fungi are also commensals of animals and humans, and they contribute to the maintenance and proper role of the natural ﬂora of higher eukaryotes. In summary, many processes cannot occur in the absence of fungi, and for these reasons, these organisms have played a key role in the evolution and development of our environment and human habits.
The “Bad” Mycology: Fungi as Mr. Hyde Unfortunately, there is also a “dark side” in the Mycology ﬁeld, because fungi are the cause of multiple phenomena that have deleterious effects for the environment and health. It is well known that some devastating plant diseases are caused by fungal pathogens and that the annual cost of crop diseases caused by fungi (such as those affecting rice, maize, tomato and others) reaches thousands of millions of dollars. Furthermore, some fungi pose a threat for other plants, such as ﬂowers and trees. In the case of animals, pathogenic fungi can also have dramatic consequences for their hosts. There are two recent examples that illustrate the importance of environmental fungal pathogens. Infections by chytrid fungi have caused a worldwide amphibian decline, and this disease has even resulted in the extinction of some frog species. Another case is the denominated white nose syndrome, which has caused the death of millions of bats in the last years. Humans are not an exception, and many fungi can cause infections in people. Classically, human pathogenic fungi have been associated with topical infections, affecting mainly the skin, nails and mucosae (oral cavity and vagina). However, in the last decades, microscopic fungi have also become a cause of life-threatening diseases in patients with risk factors, such as immunosuppression, surgery and catheters and medical implants among others. The management of these infections is limited for the low number of antifungals available in clinical practice, and the lack of suitable diagnostic techniques that provide the early development of the disease. Another issue of fungal infections is the economic cost associated, which can reach around 50,000 euros, which converts these diseases in a signiﬁcant problem for the health systems worldwide.
Reference Module in Life Sciences
Model Organisms in Biological Research Finally, it is pertinent to highlight that some of the most widely used research models in the laboratory are fungi. An excellent example is the yeast Saccharomyces cerevisiae, that has been one of the main eukaryotic models in genetics, molecular biology, cell biology, biochemistry and metabolism. Other examples are Schizosaccharomyces pombe (a key organism to understand cell cycle regulation), Aspergillus nidulans, Ustilago maydis and Neurospora crassa. Many lessons obtained from these organisms have become milestones in biological research, and in the last decade, several Nobel prices have been awarded to scientists who used fungi as model organisms to understand basic biological processes also present in higher eukaryotes, including humans. The Reference Module in Life Sciences offers an exceptional opportunity to create a comprehensive and updated section that will cover the main areas for those readers interested on fungi. The Mycology section will contain articles on fungal pathogenesis, genetics, metabolism, biochemistry, environmental interactions and biotechnology written by highly recognized scientists and experts on these ﬁelds. We hope that this section will be of interest of both specialized and non-specialized readers who want to learn about the most interesting and important aspects of fungi.