Microbiology The picture shows different color mutants of Aspergillus nidulans. Wild type forms green spores which cover almost the entire colony. It is easy to generate mutants in which pigment biosynthesis is blocked at certain stages and thus a different pigment variant (yellow) or no pigments (white) are produced. Mutants are a great starting point for a molecular analysis. This approach has been used to study many cellular processes and made A. nidulans a model organism for lower eukaryotes and beyond. The diameter of a colony is about 1 cm. less well known is that they play a vital role, not only in generating nutrients, but also in plant nutrient uptake: every metre of plant root in the soil is associated with roughly a kilometre of symbiotic fungal hyphae, known as ‘mycorrhiza’, which take up nutrients and pass them to the plant. Filamentous fungi are important pathogens of crop plants, and in a few cases cause serious human disease, particularly in the immunocompromised. They have also been harnessed for biotechnological uses, including crucially in the production of antibiotics such With the help of the jellyfish green fluorescent protein (GFP) researchers visualised the microtubule as penicillin, other medicines, citric acid, cytoskeleton in Aspergillus nidulans. Round spores and foods such as soy sauce and cheese. To produced long hyphae, and microtubules are visible as long filaments in the cells. They serve as tracks scientists, fungi are also important due to the for intracellular traffic. (picture taken by Minoas similarity of their cells to human cells, making Evangelinos, KIT) them ideal models to study various aspects of cell function. Mycology: adequate quantities of these materials to Professor Fischer, Professor Riquelme and the tip in order to keep up with the rate of their colleagues, with funding from the growth? Secondly, with such rapid growth Deutsche Forschungsgemeinschaft and occurring at the tip, how does the hypha CONACYT, are studying a host of questions maintain a stable marker of exactly where, and Unravelling the surrounding the growth and development of in what direction, growth is to occur? filamentous fungi. Using multiple species and state-of-the-art microscopy and molecular The logistics of transporting materials to biological methods, they are enhancing our the actively-growing hyphal tip are being understanding of the mechanisms by which elucidated by Michael Feldbrügge’s lab riddle of the these intriguing and important organisms at Heinrich Heine University, Düsseldorf, grow and differentiate. Germany. The length of the hyphae is traversed by a skeleton of fine tubes called KEEPING PACE WITH GROWTH microtubules, along which vesicles and their At the tip of each fungal hypha lies a region contents travel, facilitated by proteins acting filamentous fungi of active growth. Here, membrane-bound as motors. Feldbrügge has also found that particles (vesicles) containing the raw materials these provide transport routes for molecules for building new cell walls and membranes – of messenger RNA, which translate the proteins, lipids and other organic molecules, genetic information in DNA into functional as well as catalytic enzymes – fuse with the proteins. Crucially, this means that protein The fungi are perhaps the least understood of the multicellular here may be as many as five microscopic tip, to form huge networks cell’s boundary membrane, releasing their production can be precisely targeted to million species of fungi worldwide called ‘mycelia’. precious cargo. However, the highly polarised specific regions within a cell without having organisms, despite being almost ubiquitous in nature. An international – many more than there are positioning of this region poses challenges to transport large quantities of the proteins team, coordinated by Professor Dr Reinhard Fischer of the Karlsruhe plants. The vast majority of these UNDERRATED ORGANISMS for the fungus. Firstly, how can they transport themselves. Institute of Technology, Germany, and Professor Dr Meritxell little-understood organisms are Despite their lowly appearance, the Riquelme from the Centro de Investigación Cientifíca y de Educación the ‘filamentous fungi,’ named because filamentous fungi are crucial to the functioning Tthey are composed of a web of filaments of natural ecosystems. Alongside bacteria, Superior de Ensenada, Mexico, is leading attempts to understand the called ‘hyphae’. The work of Professor they are the main agents responsible for The diverse and enlightening findings of this growth and development of these remarkable organisms, shedding Fischer, Professor Riquleme and their co- decomposing dead organic matter, making high-profile programme have implications far light on their medical and ecological applications. workers focuses on how these filaments its chemical components available to the next grow, indefinitely, by extension at each generation of organisms. What is perhaps beyond the fungal kingdom 15 Microbiology Detail RESEARCH OBJECTIVES Professor Reinhard Fischer is currently How numerous, widespread and What recent technological advances studying the filamentous fungus significant are the filamentous fungi? have helped further your research? Aspergillus nidulans. His primary interest Fungi are found in nearly all ecosystems, The advent of molecular biological in this fungus is as a model for spore where they fulfil important functions methods in the 1980s, the use of GFP and mycotoxin formation and the effect for nutrient recycling. Some species and other fluorescent proteins since 1994 of environmental factors on its growth. are important plant pathogens, such as in combination with steadily improved Professor Meritxell Riquelme is studying Magnaporthe oryzae or rust fungi. There microscopy techniques and the recent the mould Neurospora crassa and is are also animal pathogens. Many moulds development of super-resolution interested in the cellular components contaminate food and feed and cause microscopy techniques have boosted enabling indefinite hyphal extension. tremendous losses due to mycotoxin fungal research. 2 µm formation. FUNDING How do the cells of filamentous fungi Deutsche Forschungsgemeinschaft Why is their growth and development differ from those of other organisms? (DFG), Consejo Nacional de Ciencia y Above: In this experiment two enzymes required Fungi are in many aspects identical to Tecnología, Mexico (CONACYT) for cell wall synthesis were visualised in hyphae of such an interesting area to study? Neurospora crassa using two different coloured The fungal hypha is able to grow human cells. One important difference, fluorescent proteins. Whereas an endoglucanase indefinitely at the tip. It is one of the however, is the presence of a rigid cell COLLABORATORS enzyme (BGT-2) localises to the plasma membrane, a chitin synthase (CHS-1) accumulates first in a structure few examples of extreme polar growth wall consisting of different carbohydrate Professors J Aguirre, M Bölker, G Braus, called “Spitzenkörper” before it is secreted. Confocal of individual cells. Other examples are polymers, including chitin. Because of M Feldbrügge, U Fleig, W Hansberg, Laser scanning microscopy images obtained by Dr pollen tubes, root hairs and nerve cells. this difference, the fungal cell wall or the A Herrera-Estrella, R Mouriño-Pérez, J Leonora Martínez-Núñez, CICESE. Thus the study of the mechanisms of biosynthesis machinery may be targets Kämper, U Kück, N Requena, N Takeshita, polar fungal extension may help to for drug development. S Bartnicki-Garcia In answer to the second question, Prof Fischer Close-up images of a colony of N. crassa. The aerial mycelium shows improve our understanding of polarity himself, working with Prof Norio Takeshita, the interwoven fine hyphae. Carotene stains the mycelium orange. in general. Likewise, simple hyphae are Pictures taken by Rosa Aurelia Fajardo Somera from KIT. What biological features are BIO has discovered that in the filamentous able to differentiate rather complicated conserved between filamentous Before becoming Professor for fungus, Aspergillus nidulans, molecules of structures such as fruiting bodies. fungi and animals such as humans? Microbiology at the University a special protein – TeaR – located at the tip This requires massive changes in gene Basic cell biological processes such of Karlsruhe, Prof Dr Reinhard of the hyphae, mark the zone in which active expression. It can be an example for as mitosis, meiosis, the functioning Fischer studied for his PhD in growth is taking place. Using advanced, other differentiation processes, e.g., of organelles, or the principles of gene Microbiology at the University of super-resolution microscopy techniques to embryogenesis in higher eukaryotes. regulation are highly conserved between Marburg. He has represented the DFG visualise the activities of living cells in real humans and both filamentous and as a panel member since 2012 and time, they showed that the cluster of TeaR yeast-like fungi. sits on the editorial boards for a molecules at the hyphal tip is repeatedly number of well-known scientific dispersed and reassembled with newly- journals, including Molecular arriving TeaRs, maintaining an indicator that Microbiology, mSphere and tells the machinery of the cell where to build mBio. Prof Dr Mertixell Riquelme new tissue. genetic approaches, that injury results in the between symbiotic partners. Arbuscule completed a BS in Biology at the production of highly reactive and damaging formation, however,