Sarah Watkinson

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• MA PhD
• Emeritus at University of Oxford

All plants are hosts to fungi that are specialised at establishing close contact with their cells and feed on the products of photosynthesis. This mode of fungal nutrition is termed biotrophy. Some biotrophs confer advantages to their hosts and are considered to be mutualistic. Mycorrhizal fungi sustain terrestrial ecosystems through mutualisms wit...

Research on fungal diversity, ecology and evolution increasingly involves molecular methods. Using nucleic acid sequence data, otherwise undetectable fungi present in environmental samples can be identified and assigned phylogenetically. Diagnostic PCR can detect human and crop pathogens present at very low levels. The rapid rate at which new funga...

Fungi require a carbon source, assimilable nitrogen, and other essential elements. As osmotrophs, they acquire nutrients in soluble form and can dissolve natural polymers. Plant material supplies the carbon requirements of most fungi, and species phylogeny is strongly associated with the evolution of an enzyme repertoire suited to saprotrophic, mut...

The Fungi, Third Edition, offers a comprehensive and thoroughly integrated treatment of the biology of the fungi. This modern synthesis highlights the scientific foundations that continue to inform mycologists today, as well as recent breakthroughs and the formidable challenges in current research. The Fungi combines a wide scope with the depth of...

The restoration of microbial communities may be central to the re-establishment of plant–soil interactions and renovation of function in degraded woodland systems. However, there is currently little knowledge of the extent to which the soil microbial communities associated with past vegetation persist in such systems. This study used fungal-specifi...

Serpula lacrymans, the causative agent of dry rot timber decay in buildings, is a Basidiomycete fungus in the Boletales clade. It owes its destructiveness to a uniquely well-developed capacity to colonize by rapid mycelial spread from sites of initial spore infection, coupled with aggressive degradation of wood cellulose. Genomic methods have recen...

Brown rot decay removes cellulose and hemicellulose from wood—residual lignin contributing up to 30% of forest soil carbon—and is derived from an ancestral white rot saprotrophy in which both lignin and cellulose are decomposed. Comparative and functional genomics of the “dry rot” fungus Serpula lacrymans, derived from forest ancestors, demonstrate...

Anthropogenic nitrogen (N) deposition affects many natural processes, including forest litter decomposition. Saprotrophic fungi are the only organisms capable of completely decomposing lignocellulosic (woody) litter in temperate ecosystems, and therefore the responses of fungi to N deposition are critical in understanding the effects of global chan...

Dead wood litter input to mature forest ecosystems represents 30–40% of the total biomass, containing about 1–4 and 0.1–0.8 kg/(ha∙year), of N and P, respectively. However, since wood decomposes relatively slowly, it represents a much larger proportion of the standing crop of plant litter on the forest floor, forming a large reservoir of mineral nu...

Introduction Basidiomycete species are a key component in wood degradation and have a great influence in carbon cycling. Two major mechanisms of wood decay have been characterized, termed white rot and brown rot. White rot species effectively degrade lignin, cellulose and hemicellulose while brown rot species degrade mainly the latter two component...

Growth and organelle morphology in the wood rotting basidiomycete fungus Phanerochaete velutina were examined in Petri dishes, on agar-coated slides, and in submerged cultures, using DIC, fluorescence and four-dimensional (4-D; x,y,z,t) confocal microscopy, with several fluorescent probes. Phanerochaete is ideal for this work because of its fast gr...

Sequestration and release of carbon in the decomposer subsystem of the forest floor are key ecosystem functions of saprotrophic basidiomycetes. Both are the result of fungal metabolic processes commonly regulated by nitrogen availability. Saprotrophic basidiomycetes are the primary wood decomposer organisms in N-limited boreal and temperate forests...

Basidiomycota comprise the most morphologically complex group of macrofungi. They include mushrooms and toadstools, and rust and smut parasites of plants. Basidiomycetes grow as networks of hyphae colonizing nutrient substrates. Reproduction is by airborne spores produced from basidiomes such as mushrooms. Features used in identification show frequ...

Transport networks are vital components of multi-cellular organisms, distributing nutrients and removing waste products. Animal cardiovascular and respiratory systems, and plant vasculature, are branching trees whose architecture is thought to determine universal scaling laws in these organisms. In contrast, the transport systems of many multi-cell...

Saprotrophic woodland fungi forage for mineral nutrients and woody resources by extension of a mycelial network across the forest floor. Different species explore at different rates and establish networks with qualitatively differing architecture. However, detailed understanding of fungal foraging behaviour has been hampered by the absence of tools...

alpha-Aminoisobutyric acid (AIB) is a nonmetabolized amino acid analogue of alanine, which at low (muM) concentrations acts as a tracer for amino acid movements. At high concentrations (mM), it competitively inhibits membrane transport and metabolism of protein amino acids and acts as a systemic translocated inhibitor of mycelial extension in fungi...

By preventing amino acid translocation through mycelial networks, the spread of wood decay fungi within building structures can be contained, and sound joinery protected from attack. The amino acid analogue AIB (α-aminoisobutyric acid) competitively excludes utilisable amino acids from the mycelium, and from the nutrient supply network of mycelial...

Fungi are the principal degraders of biomass in most terrestrial ecosystems. In contrast to surface environments, deep-sea environmental gene libraries have suggested that fungi are rare and non-diverse in high-pressure marine environments. Here, we report the diversity of fungi from 11 deep-sea samples from around the world representing depths fro...

Fungi play a central role in the nutrient cycles of boreal and temperate forests. In these biomes, the saprotrophic wood-decay fungi are the only organisms that can completely decompose woody plant litter. In particular, cord-forming basidiomycete fungi form extensive mycelial networks that scavenge scarce mineral nutrients and translocate them ove...

Microorganisms display a range of oscillatory phenomena that operate over different temporal scales. Fourier analysis provides a compact description of such oscillations in terms of their frequency, magnitude and phase. However, in the majority of studies there is no explicit consideration of the spatial organisation of the oscillation. Here we des...

Fungi are of fundamental importance in the terrestrial environment. They have roles as decomposers, plant pathogens, symbionts, and in elemental cycles. Fungi are often dominant, and in soil can comprise the largest pool of biomass (including other microorganisms and invertebrates). They also play a role in maintenance of soil structure due to thei...

Mycelial fungi have a growth form which is unique among multicellular organisms. The data presented here suggest that they have developed a unique solution to internal solute translocation involving a complex, extended vacuole. In all filamentous fungi examined, this extended vacuole forms an interconnected network, dynamically linked by tubules, w...

Experiments were carried out on the conditions favouring strand formation in the mycelium of Serpula lacrimans. The mechanism of strand production proposed by Garrett and Butler (1960) was taken as a working hypothesis. Colonies of the fungus were grown on a liquid medium of a nutrient composition found previously to induce stranding. In one set of...

Introduction The mycelium of woodland fungi can act both as a reservoir and as a distribution system for nutrients, owing to its physiological and developmental adaptations to life at the interface between organic and mineral soil horizons. The mobility of accumulated nitrogen and phosphorus within the mycelial networks of cord-forming wood decay f...

Despite their functional importance, little is known about how and where fungi can be conserved. It is important that we understand the consequences of habitat degradation and fragmentation for fungal assemblages if we are to devise successful conservation strategies. We investigated the effects of fragmentation and disturbance on the diversity and...

Fungi play a key role in ecosystem nutrient cycles by scavenging, concentrating, translocating and redistributing nitrogen. To quantify and predict fungal nitrogen redistribution, and assess the importance of the integrity of fungal networks in soil for ecosystem function, we need better understanding of the structures and processes involved. Until...

Cord‐forming woodland basidiomycete fungi form extensive, interconnected mycelial networks that scavenge nitrogen (N) efficiently. We have developed techniques to study N dynamics in such complex mycelial systems in vivo . Uptake and distribution of the nonmetabolised, ¹⁴ C‐labelled amino‐acid analogue, α‐aminoisobutyrate ( ¹⁴ C‐AIB) was continuous...

Nitrogen translocation by woodland fungi is ecologically important, however, techniques to study long‐distance amino‐acid transport in mycelia currently have limited spatial and temporal resolution. We report a new continuous, noninvasive imaging technique for β‐emitters that operates with submillimetre spatial resolution and a practical sampling i...

This chapter emphasizes fungal genetics and evolution. Three concepts for population genetics are individual, population, and species. The sexual process in fungi involves three key steps: cell fusion, nuclear fusion and meiosis. The five basic types of life cycle in fungi are haploid, haploid-dikaryotic, haploid–diploid, diploid, and asexual proce...

This chapter emphasizes the composition, structure, growth and form of fungal cells. The hyphae of a single species can differ considerably in diameter, depending on environmental conditions, their position in a colony, and the age of the colony. The hyphae of fungi are divided into compartments by crosswall. The hyphal compartments may contain one...

This chapter provides an excellent account of fungal diversity. Genera can be grouped into families, families into orders, orders into classes, and classes into phyla. Fungi studied by mycologists include organisms from three kingdoms, Chromista, Protozoa, and Fungi. Protozoa include cellular slime moulds and plasmodial slime moulds. Chromistas are...

This chapter provides an overview of fungi, which is similar to the cultivated mushroom, Agaricus bisporus, grown commercially on a very large scale and also survives in nature. The role of edible fruit bodies is the production of large numbers of spores that are borne on the gills below the cap, and the stalk raises fruit body above the ground to...

This chapter summarizes on the production of spores, called sporulation, dormacy, and disposal. Sexual sporulation is sometimes referred to as “sexual reproduction” and asexual sporulation as “asexual reproduction.” Spores have two major roles in the life of the fungus—dispersal to a new site or survival until favourable conditions return. Sporulat...

This chapter deals with Saprotrophs, a group of fungi that is responsible for recycling the components of dead plants; the decomposition of animals remains and microorganisms (including fungi and bacteria) is accomplished mainly by bacteria. The nutrients taken up by fungi can be used directly in metabolism, or stored. Fungi need nitrogen to synthe...

This chapter provides an overview of symbiotic relationships, including parasitic, in which only one species benefits, and mutualistic, where both partners benefit. A parasite that causes perceptible damage to its host is termed a pathogen. The fungi that live as airborne symbionts of aerial plant surfaces depend on the effectiveness of their mecha...

This chapter opens with a discussion of fungi and their biotechnological applications in enzymes, alcoholic beverage, mushroom, single cell protein, yeast biomass, fermented products, agrochemicals, citric acid, vitamins, antibiotics, and pharmaceutical drugs industries. Fermentation technology is concerned with large-scale culture of microorganism...

Serpula lacrymans is a basidiomycete cord-forming wood decay fungus which reallocates nitrogen within an extensive perennial mycelial system in response to spatial discontinuities in external nutrient supply. Intracellular stored protein is mobilised by conversion to amino acids at nutrient-poor sites within a mycelium or when a whole mycelium is s...

Proteolytic enzyme activities of the wood-decaying basidiomycetes Serpula lacrymans and Coriolus versicolor, have been characterized using azocasein as substrate and by electrophoretic analysis with gelatin-containing polyacrylamide gels (gelatin-SDS-PAGE). In S. lacrymans, intracellular and extracellular azocaseinase activity was optimal at pH 5-6...

Two tests were carried out on the use of 2-aminoisobutyric acid (AIB) in limiting the spread of the dry rot fungus Serpula lacrymans in buildings when it is applied at one point in the mycelium. To reproduce as far as possible the conditions under which S. lacrymans grows in buildings, the experimental chamber for both tests was a cellar. In the fi...

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Scanning proton microprobe analysis was used to investigate the spatial distribution of elements at the cellular level in leaf cells of Sphagnum squarrosum Crome. Light micrographs of the areas scanned enabled cell types to be identified and the cellular locations characterised. The scans revealed that iron was bound at high concentrations in extra...

Recent developments in technology have enabled the scanning proton microprobe to scan at submicron spatial resolution on a routine basis. The use of the powerful combination of techniques PIXE (proton induced X-ray emission), nuclear (or Rutherford) backscattering (RBS), and secondary electron detection operating at this resolution will open up new...

The amino acid analogue α-aminoisobutyric acid (AIB) decreased linear extension growth in fifteen out of sixteen wood decay and wood spoilage fungi. In Serpula lacrimans inhibition of extension growth by AIB was accompanied by an increase in the frequency with which the hyphae of the fungus initiated branches. AIB was shown to have a preservative e...

Proteinase activity was detected in culture filtrates of eight wood-decaying basidiomycete fungi and compared in terms of ability to clear skimmed milk agar. All the fungi were proteolytic, but to differing extents. Five were compared using azocasein hydrolysis as a measure of proteolytic activity at the centres and margins of agar-grown colonies a...

Mycelium grown on medium containing either 7·5 or 0·075 mm ammonium sulphate as sole nitrogen source was separated into soluble and insoluble fractions and the amino acid compositions of extracts and hydrolysed residues were determined. Mycelial strands grown from wood were also analysed. Glutamic acid, and possibly glutamine and pyroglutamate, wer...

Mycelium of Serpula lacrimans accumulated 14C-labelled α-aminoisobutyric acid (AIB) against a concentration gradient but did not metabolise it, or incorporate it into protein. Uptake of glutamic acid was inhibited in the presence of AIB to an extent proportional to the logarithm of its concentration. Translocation of AIB occurred in the mycelium ov...

Initial stages of mycelial strand development of Serpula lacrimans in culture were compared with the structure of mature strands from infected timber. The mature strands differed from the three- to six-week-old ones in consisting preponderantly of a matrix of extrahyphal material and dead cell walls, surrounding channels of 10–25 μm diam. Also pres...

S ummary The effect of sodium nitrate level on three parameters of growth of Serpula lacrimans was investigated and compared with nitrogen levels normal in wood. The results showed that mycelial extension from a wood food base over non‐nutrient substrata is probably not limited by nitrogen availability, but that the rate of increase in mycelial bio...

The morphogenetic effect of glutamate on coremium primordium development in Penicillium claviforme could be explained by the effect that changes in external glutamate concentration had upon its accumulation and incorporation. Serine, which supported equal increases in dry weight and protein content, did not show so close a dependence of uptake rate...

Amino acids added to the growth medium stimulated development of coremium primordia in mycelium of Penicillium claviforme. Casein hydrolysate, l-asparagine, l-serine, l-glutamine, l-proline, l-hydroxyproline, l-glutamate and glycine accelerated development and also increased the final number of primordia per unit area of mycelium. A nearly linear r...

Coremia of Penicillium claviforme develop in three stages; primordium formation, elongation, and sporulation. Primordium formation was induced by external nutrients, while starvation initiated the differentiation of primordia into coremia with sporeheads. There is strong evidence that external nutrients are not taken up during this differentiation....

With sucrose and aspartate as carbon and nitrogen sources respectively, stranding was greatest on media with high sucrose and low aspartate concentrations, but the greatest mycelial growth occurred when both were high. With nitrate or ammonium as sole nitrogen sources more strands were produced than on aspartate and there was also more autolysis. T...

Microorganisms display a range of oscillatory phenomena that operate over different temporal scales. Fourier analysis provides a compact description of such oscillations in terms of their frequency, magnitude and phase. However, in the majority of studies there is no explicit consideration of the spatial organisation of the oscillation. Here we des...