1,720,958 research outputs found
Marine fungal traits: towards a functional understanding of pelagic fungal ecology
No full textFungal life has been detected in practically every ecosystem explored to date, amounting to an estimated 12 Gt C or 2% of the total biomass on Earth. Fungi fulfil a number of functional roles in terrestrial ecosystem processes, through the decomposition of complex organic matter, remineralisation of carbon and other nutrients, and various interactions with other organisms. Marine environments harbour phylogenetically diverse fungal communities, including many taxa also found on land, but comparatively little is known about the functional ecology of marine fungi, particularly in the pelagic open ocean. DNA-based studies have demonstrated spatial and temporal variability in pelagic fungal abundance and community composition, correlating with multiple environmental factors including phytoplankton abundance, temperature, oxygen and nutrient concentrations. However, physiological evidence of pelagic fungal growth responses to changing conditions is currently lacking, precluding the establishment of mechanistic relationships between environmental gradients, pelagic fungal activity, and ecosystem function. This thesis aims to develop a functional understanding of pelagic marine fungal ecology, drawing upon existing functional trait-based approaches from terrestrial fungal and marine plankton ecology. A combination of culture-dependent and independent methods are applied to investigate fungal diversity and activity throughout the water column at the Porcupine Abyssal Plain Sustained Observatory (PAP-SO) – an open ocean site in the North-East Atlantic. Environmentally relevant pelagic fungal isolates are selected based on their in situ activity and cultured under a range of experimental conditions in the laboratory to characterise their physiological and morphological traits. Growth responses to variable conditions are compared between isolates and between taxa, with the aim of identifying general, predictable patterns of pelagic fungal trait variation along environmental gradients. Pelagic fungal isolates demonstrate physiological and morphological plasticity in response to variable temperature, salinity and resource availability. Filamentous isolates vary in colony extension rate and mycelial density, with a temperature-dependent rate-density relationship. Yeast-like isolates vary in growth rate and biomass yield, with a temperature-dependent rate-yield relationship. Salinity and carbon substrate responses are relatively isolate-specific. Unicellular yeast Naganishia diffluens, active throughout the water column at PAP-SO, is able to utilise a broad diversity of nitrogen sources including nitrate, and responds to low nitrogen availability by decreasing in growth rate and cell size. Polymorphic yeast Aureobasidium pullulans only develops filamentous growth at high substrate concentrations, while budding yeast-type cells also show dynamic size and shape responses to substrate availability. This work provides novel insight into the ecophysiology of pelagic marine fungi, highlighting the potential for fungal activity, and therefore ecological and biogeochemical functions, to vary along environmental gradients in the ocean
Cell morphological plasticity in response to substrate availability of a cosmopolitan polymorphic yeast from the open ocean
No full textPolymorphic yeasts can switch between unicellular division and multicellular filamentous growth. Although prevalent in aquatic ecosystems, such as the open ocean, we have a limited understanding of the controlling factors on their morphological variation in an aquatic ecology context. Here we show that substrate concentration regulates cell morphogenesis in a cosmopolitan polymorphic yeast, Aureobasidium pullulans, isolated from the pelagic open ocean and analyzed in liquid batch culture. Filamentous cell development was triggered only under high initial substrate conditions, suggesting that hyphal growth could be more advantageous under eutrophic conditions and may influence pelagic fungal interactions with particulate organic matter. Filamentous growth proportionally declined before the exhaustion of substrate and before budding yeast-type cell division entered stationary phase, possibly modulated by quorum sensing as previously evidenced in other polymorphic yeasts. We also found that budding yeast-type unicells decreased in size and became more elongated in shape in response to substrate depletion, resulting in higher cell surface area to volume ratios, which could affect yeast dispersal and/or provide a nutrient uptake advantage under oligotrophic conditions. Our results demonstrate resource-responsive morphological plasticity in a marine-derived polymorphic yeast, providing mechanistic insight into the ability of fungi to survive fluctuating environmental conditions such as in the open ocean.</p
Physiological and morphological plasticity in response to nitrogen availability of a yeast widely distributed in the open ocean
Get PDFYeasts are prevalent in the open ocean, yet we have limited understanding of their ecophysiological adaptations, including their response to nitrogen availability, which can have a major role in determining the ecological potential of other planktonic microbes. In this study, we characterised the nitrogen uptake capabilities and growth responses of marine-occurring yeasts. Yeast isolates from the North Atlantic Ocean were screened for growth on diverse nitrogen substrates, and across a concentration gradient of three environmentally relevant nitrogen substrates: nitrate, ammonium, and urea. Three strains grew with enriched nitrate while two did not, demonstrating that nitrate utilisation is present but not universal in marine yeasts, consistent with existing knowledge of non-marine yeast strains. Naganishia diffluens MBA_F0213 modified the key functional trait of cell size in response to nitrogen concentration, suggesting yeast cell morphology changes along chemical gradients in the marine environment. Meta-analysis of the reference DNA barcode in public databases revealed that the genus Naganishia has a global ocean distribution, strengthening the environmental applicability of the culture-based observations. This study provides novel quantitative understanding of the ecophysiological and morphological responses of marine-derived yeasts to variable nitrogen availability in vitro, providing insight into the functional ecology of yeasts within pelagic open ocean environment
Dataset for Marine Fungal Traits: Towards a Functional Understanding of Pelagic Fungal Ecology
No full textThis data was collected/created through field sampling and laboratory experiments.
Data and samples were initially collected as part of RRS Discovery Cruise DY103, June-July 2019.
Environmental samples were processed at the Marine Biological Association, Plymouth UK.
Environmental fungal isolates were characterised through laboratory growth experiments.
Date of data collection: 2019-2024
Associated publications:
Diver, P., Ward, B.A. and Cunliffe, M. (2024) Physiological and morphological plasticity in response to nitrogen availability of a yeast widely distributed in the open ocean. FEMS Microbiology Ecology. https://doi.org/10.1093/femsec/fiae053
Diver, P., Ward, B.A. and Cunliffe, M. (2024) Cell morphological plasticity in response to substrate availability of a cosmopolitan polymorphic yeast from the open ocean. Mycologia. https://doi.org/10.1080/00275514.2024.2418784</span
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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