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Frank H. Gleason - One of the best experts on this subject based on the ideXlab platform.
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Key Ecological Roles for Zoosporic True Fungi in Aquatic Habitats
Microbiology spectrum, 2017Co-Authors: Frank H. Gleason, Osu Lilje, Bettina Scholz, Thomas G. Jephcott, Floris Van Ogtrop, Linda Henderson, Sandra Kittelmann, Deborah J. MacarthurAbstract:The diversity and abundance of Zoosporic true Fungi have been analyzed recently using fungal sequence libraries and advances in molecular methods, such as high-throughput sequencing. This review focuses on four evolutionary primitive true fungal phyla: the Aphelidea, Chytridiomycota, Neocallimastigomycota, and Rosellida (Cryptomycota), most species of which are not polycentric or mycelial (filamentous), rather they tend to be primarily monocentric (unicellular). Zoosporic Fungi appear to be both abundant and diverse in many aquatic habitats around the world, with abundance often exceeding other fungal phyla in these habitats, and numerous novel genetic sequences identified. Zoosporic Fungi are able to survive extreme conditions, such as high and extremely low pH; however, more work remains to be done. They appear to have important ecological roles as saprobes in decomposition of particulate organic substrates, pollen, plant litter, and dead animals; as parasites of zooplankton and algae; as parasites of vertebrate animals (such as frogs); and as symbionts in the digestive tracts of mammals. Some chytrids cause economically important diseases of plants and animals. They regulate sizes of phytoplankton populations. Further metagenomics surveys of aquatic ecosystems are expected to enlarge our knowledge of the diversity of true Zoosporic Fungi. Coupled with studies on their functional ecology, we are moving closer to unraveling the role of Zoosporic Fungi in carbon cycling and the impact of climate change on Zoosporic fungal populations.
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Quantitative methods for the analysis of Zoosporic Fungi.
Journal of Microbiological Methods, 2012Co-Authors: Agostina Marano, Serena Rasconi, Frank H. Gleason, Felix Bärlocher, Carmen L.a Pires-zottarelli, Osu Lilje, Steve K. Schmidt, Maiko Kagami, Marcelo D. Barrera, Télesphore Sime-ngandoAbstract:Quantitative estimations of Zoosporic Fungi in the environment have historically received little attention, primarily due to methodological challenges and their complex life cycles. Conventional methods for quantitative analysis of Zoosporic Fungi to date have mainly relied on direct observation and baiting techniques, with subsequent fungal identification in the laboratory using morphological characteristics. Although these methods are still fundamentally useful, there has been an increasing preference for quantitative microscopic methods based on staining with fluorescent dyes, as well as the use of hybridization probes. More recently however PCR based methods for profiling and quantification (semi- and absolute) have proven to be rapid and accurate diagnostic tools for assessing Zoosporic fungal assemblages in environmental samples. Further application of next generation sequencing technologies will however not only advance our quantitative understanding of Zoosporic fungal ecology, but also their function through the analysis of their genomes and gene expression as resources and databases expand in the future. Nevertheless, it is still necessary to complement these molecular-based approaches with cultivation-based methods in order to gain a fuller quantitative understanding of the ecological and physiological roles of Zoosporic Fungi.
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diversity role in decomposition and succession of Zoosporic Fungi and straminipiles on submerged decaying leaves in a woodland stream
Hydrobiologia, 2011Co-Authors: Agostina V Marano, Carmen Lidia Amorim Pireszottarelli, Marcelo Daniel Barrera, Monica Mirta Steciow, Frank H. GleasonAbstract:Leaf litter is a very important primary source of energy in woodland streams. Decomposition of leaf litter is a process mediated by many groups of microorganisms which release extracellular enzymes for the degradation of complex macromolecules. In this process, true Fungi and straminipiles are considered to be among the most active groups, more active than the bacteria, at least during the early stages of the process. Colonization increases the quality of the leaves as a food resource for detritivores. In this way, matter and energy enter detritus-based food chains. Previously, aquatic hyphomycetes were considered to be the major fungal group responsible for leaf litter decomposition. Although Zoosporic Fungi and straminipiles are known to colonize and decompose plant tissues in various environments, there is scant information on their roles in leaf decomposition. This study focuses on the communities of Zoosporic Fungi and straminipiles in a stream which are involved in the decomposition of leaves of two plant species, Ligustrum lucidum and Pouteria salicifolia, in the presence of other groups of Fungi. A characteristic community dominated by Nowakowskiella elegans, Phytophthora sp., and Pythium sp. was found. Changes in the fungal community structure over time (succession) was observed: terrestrial mitosporic Fungi appeared during the early stages, Zoosporic Fungi, straminipiles, and aquatic Hyphomycetes in early-to-intermediate stages, while representatives of the phylum Zygomycota were found at early and latest stages of the decomposition. These observations highlight the importance of Zoosporic Fungi and straminipiles in aquatic ecosystems.
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Hidden diversity among aquatic heterotrophic flagellates: ecological potentials of Zoosporic Fungi
Hydrobiologia, 2011Co-Authors: Télesphore Sime-ngando, Emilie Lefevre, Frank H. GleasonAbstract:Since the emergence of the ‘microbial loop’ concept, heterotrophic flagellates have received particular attention as grazers in aquatic ecosystems. These microbes have historically been regarded incorrectly as a homogeneous group of bacterivorous protists in aquatic systems. More recently, environmental rDNA surveys of small heterotrophic flagellates in the pelagic zone of freshwater ecosystems have provided new insights. (i) The dominant phyla found by molecular studies differed significantly from those known from morphological studies with the light microscope, (ii) the retrieved phylotypes generally belong to well-established eukaryotic clades, but there is a very large diversity within these clades and (iii) a substantial part of the retrieved sequences cannot be assigned to bacterivorous but can be assigned instead to parasitic and saprophytic organisms, such as Zoosporic true Fungi (chytrids), fungus-like organisms (stramenopiles), or virulent alveolate parasites (Perkinsozoa and Amoebophrya sp.). All these microorganisms are able to produce small zoospores to assure dispersal in water during their life-cycles. Based on the existing literature on true Fungi and fungus-like organisms, and on the more recently published eukaryotic rDNA environmental studies and morphological observations, we conclude that previously overlooked microbial diversity and related ecological potentials require intensive investigation (i) for an improved understanding of the roles of heterotrophic flagellates in pelagic ecosystems and (ii) to properly integrate the concept of ‘the microbial loop’ into modern pelagic microbial ecology.
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Can Zoosporic true Fungi grow or survive in extreme or stressful environments?
Extremophiles, 2010Co-Authors: Frank H. Gleason, Steve K. Schmidt, Agostina V MaranoAbstract:Zoosporic true Fungi are thought to be ubiquitous in many ecosystems, especially in cool, moist soils and freshwater habitats which are rich in organic matter. However, some of the habitats where these Fungi are found may periodically experience extreme conditions, such as soils in extremely dry, hot and cold climates, acidic and alkaline soils, polluted rivers, anaerobic soil and water, saline soil and water, periglacial soils, oligotrophic soils, tree canopies and hydrothermal vents. It is clear that many ecotypes of Zoosporic true Fungi have indeed adapted to extreme or stressful environmental conditions. This conclusion is supported by studies in both the field and in the laboratory. Therefore, in our opinion, at least some true Zoosporic Fungi can be considered to be extremophiles.
Télesphore Sime-ngando - One of the best experts on this subject based on the ideXlab platform.
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Quantitative methods for the analysis of Zoosporic Fungi.
Journal of Microbiological Methods, 2012Co-Authors: Agostina Marano, Serena Rasconi, Frank H. Gleason, Felix Bärlocher, Carmen L.a Pires-zottarelli, Osu Lilje, Steve K. Schmidt, Maiko Kagami, Marcelo D. Barrera, Télesphore Sime-ngandoAbstract:Quantitative estimations of Zoosporic Fungi in the environment have historically received little attention, primarily due to methodological challenges and their complex life cycles. Conventional methods for quantitative analysis of Zoosporic Fungi to date have mainly relied on direct observation and baiting techniques, with subsequent fungal identification in the laboratory using morphological characteristics. Although these methods are still fundamentally useful, there has been an increasing preference for quantitative microscopic methods based on staining with fluorescent dyes, as well as the use of hybridization probes. More recently however PCR based methods for profiling and quantification (semi- and absolute) have proven to be rapid and accurate diagnostic tools for assessing Zoosporic fungal assemblages in environmental samples. Further application of next generation sequencing technologies will however not only advance our quantitative understanding of Zoosporic fungal ecology, but also their function through the analysis of their genomes and gene expression as resources and databases expand in the future. Nevertheless, it is still necessary to complement these molecular-based approaches with cultivation-based methods in order to gain a fuller quantitative understanding of the ecological and physiological roles of Zoosporic Fungi.
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Hidden diversity among aquatic heterotrophic flagellates: ecological potentials of Zoosporic Fungi
Hydrobiologia, 2011Co-Authors: Télesphore Sime-ngando, Emilie Lefevre, Frank H. GleasonAbstract:Since the emergence of the ‘microbial loop’ concept, heterotrophic flagellates have received particular attention as grazers in aquatic ecosystems. These microbes have historically been regarded incorrectly as a homogeneous group of bacterivorous protists in aquatic systems. More recently, environmental rDNA surveys of small heterotrophic flagellates in the pelagic zone of freshwater ecosystems have provided new insights. (i) The dominant phyla found by molecular studies differed significantly from those known from morphological studies with the light microscope, (ii) the retrieved phylotypes generally belong to well-established eukaryotic clades, but there is a very large diversity within these clades and (iii) a substantial part of the retrieved sequences cannot be assigned to bacterivorous but can be assigned instead to parasitic and saprophytic organisms, such as Zoosporic true Fungi (chytrids), fungus-like organisms (stramenopiles), or virulent alveolate parasites (Perkinsozoa and Amoebophrya sp.). All these microorganisms are able to produce small zoospores to assure dispersal in water during their life-cycles. Based on the existing literature on true Fungi and fungus-like organisms, and on the more recently published eukaryotic rDNA environmental studies and morphological observations, we conclude that previously overlooked microbial diversity and related ecological potentials require intensive investigation (i) for an improved understanding of the roles of heterotrophic flagellates in pelagic ecosystems and (ii) to properly integrate the concept of ‘the microbial loop’ into modern pelagic microbial ecology.
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Fluorescence in situ hybridization of uncultured Zoosporic Fungi: Testing with clone-FISH and application to freshwater samples using CARD-FISH
Journal of Microbiological Methods, 2010Co-Authors: Marlene Jobard, Serena Rasconi, Télesphore Sime-ngandoAbstract:Recently, molecular environmental surveys of the eukaryotic microbial community in lakes have revealed a high diversity of sequences belonging to uncultured Zoosporic Fungi commonly known as chytrids. These microorganisms have two different stages in their life cycle and are known as algal parasites (i.e. host-attached infective sporangia) and as food sources for zooplankton (i.e. free-living zooflagellate propagules) in aquatic systems. However, because of their small size and their lack of distinctive morphological features, traditional microscopy does not allow the detection of chytrids, particularly of zoospores which have probably been misidentified as phagotrophic flagellates in previous studies. Hence, quantitative data on chytrids in natural environments is missing. We have adapted a clone-FISH approach known from prokaryotes to optimize the hybridization conditions of a designed oligonucleotidic probe specific to Chytridiales (i.e. the largest group of the true-fungal division of Chytridiomycota), before application to natural samples using the CARD-FISH approach. When these conditions were applied, the CARD-FISH assay demonstrated high specificity and sensitivity, and offers a promising tool for quantitative assessment of natural Zoosporic Fungi, primarily of zoospores which contributed up to 60% of the total abundance of heterotrophic flagellates. Although the field results from the CARD-FISH approach were considered preliminary and mainly as 'proof of concept', findings were consistent with ecological considerations known from pelagic habitats and host versus parasite populations, with recurrent ecological patterns in two contrasting lake ecosystems. We conclude that this approach will contribute to a better understanding of the ecological significance of Zoosporic organisms in microbial food webs of pelagic ecosystems.
W S Borneman - One of the best experts on this subject based on the ideXlab platform.
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biology fiber degradation and enzymology of anaerobic Zoosporic Fungi
Critical Reviews in Microbiology, 1993Co-Authors: D A Wubah, D E Akin, W S BornemanAbstract:AbstractAnaerobic zoospore-producing Fungi that inhabit the gastrointestinal tract of herbivores, especially ruminants, have recently been discovered. These Fungi have been isolated from the rumen, hind gut, and the feces of ruminants. Thirteen species, belonging to five genera, of these Fungi have been assigned to the class Chytridiomycetes. These species arc classified according to the number of flagella on the zoospores and the types of thalli that develop from the zoospores. Their life cycle consists of a zoospore that encysts and develops into a vegetative thallus with zoosporangia, which at times become resting sporangia. These Fungi produce a wide range of active hydrolytic enzymes, notably cellulases and xylanases, that provide them with the potential to degrade the major structural polysaccharides in plant cell walls. Their cellulases are among the most active reported to date and solubilize both amorphous and highly ordered cellulose. Their esterases are active against both feruloyl and p-coumar...
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biology fiber degradation and enzymology of anaerobic Zoosporic Fungi
Critical Reviews in Microbiology, 1993Co-Authors: D A Wubah, D E Akin, W S BornemanAbstract:Anaerobic zoospore-producing Fungi that inhabit the gastrointestinal tract of herbivores, especially ruminants, have recently been discovered. These Fungi have been isolated from the rumen, hind gut, and the feces of ruminants. Thirteen species, belonging to five genera, of these Fungi have been assigned to the class Chytridiomycetes. These species are classified according to the number of flagella on the zoospores and the types of thalli that develop from the zoospores. Their life cycle consists of a zoospore that encysts and develops into a vegetative thallus with zoosporangia, which at times become resting sporangia. These Fungi produce a wide range of active hydrolytic enzymes, notably cellulases and xylanases, that provide them with the potential to degrade the major structural polysaccharides in plant cell walls. Their cellulases are among the most active reported to date and solubilize both amorphous and highly ordered cellulose. Their esterases are active against both feruloyl and p-coumaroyl arabinoxylans, which provides an advantage in degrading poorly biodegradable cell walls. They degrade lignin-containing cell walls, but do not metabolize the lignin moiety. Rhizoids of vegetative thalli penetrate cell walls, and they are better able than bacteria or protozoa to attack recalcitrant tissues and weaken the textural strength of plant material.
Maiko Kagami - One of the best experts on this subject based on the ideXlab platform.
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temporal variation in community structure of Zoosporic Fungi in lake biwa japan
Aquatic Microbial Ecology, 2021Co-Authors: Peixue Song, Maiko Kagami, Shoko Tanabe, Naoshige Goto, Kensuke Seto, Syuhei BanAbstract:Zoosporic Fungi play an important role in aquatic environments, but their diversity, especially that of parasitic Fungi of phytoplankton, has still not been fully revealed. We conducted monthly analyses of the community structure of Zoosporic Fungi at a pelagic site in Lake Biwa, Japan, from May to December 2016. Metabarcoding analysis, targeted to a large subunit region of ribosomal DNA in the nano-size fraction of particles (2-20 µm), was carried out on the samples. We also counted large phytoplankton and chytrid sporangia attached to the hosts. We detected 3 Zoosporic fungal phyla (Blastocladiomycota, Chytridiomycota and Cryptomycota) within 107 operational taxonomic units (OTUs), in which Chytridiomycota was the most diverse and abundant phylum. Few fungal OTUs overlapped between months, and specific communities were detected in each month. These results showed that diverse Zoosporic Fungi with high temporal variability inhabited the lake. Five large phytoplankton species were found to be infected by chytrids: Staurastrum dorsidentiferum, S. rotula, Closterium aciculare, Asterionella formosa and Aulacoseira granulata. Some chytrids were detected by metabarcoding analysis: Zygophlyctis asterionellae infecting A. formosa, Staurastromyces oculus infecting S. dorsidentiferum and Pendulichytrium sphaericum infecting A. granulata. One OTU detected in association with infected C. aciculare by microscopic counting might have been an obligate parasitic chytrid of C. aciculare. The results indicated that a combination of metabarcoding and microscopic analysis revealed more information on Zoosporic Fungi, including those that are parasitic.
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evaluation of daphnid grazing on microscopic Zoosporic Fungi by using comparative threshold cycle quantitative pcr
Applied and Environmental Microbiology, 2016Co-Authors: Michelle A Maier, Kimiko Uchii, Tawnya D Peterson, Maiko KagamiAbstract:ABSTRACT Lethal parasitism of large phytoplankton by chytrids (microscopic Zoosporic Fungi) may play an important role in organic matter and nutrient cycling in aquatic environments by shunting carbon away from hosts and into much smaller zoospores, which are more readily consumed by zooplankton. This pathway provides a mechanism to more efficiently retain carbon within food webs and reduce export losses. However, challenges in accurate identification and quantification of chytrids have prevented a robust assessment of the relative importance of parasitism for carbon and energy flows within aquatic systems. The use of molecular techniques has greatly advanced our ability to detect small, nondescript microorganisms in aquatic environments in recent years, including chytrids. We used quantitative PCR (qPCR) to quantify the consumption of zoospores by Daphnia in laboratory experiments using a culture-based comparative threshold cycle ( C T ) method. We successfully quantified the reduction of zoospores in water samples during Daphnia grazing and confirmed the presence of chytrid DNA inside the daphnid gut. We demonstrate that comparative C T qPCR is a robust and effective method to quantify zoospores and evaluate zoospore grazing by zooplankton and will aid in better understanding how chytrids contribute to organic matter cycling and trophic energy transfer within food webs. IMPORTANCE The study of aquatic Fungi is often complicated by the fact that they possess complex life cycles that include a variety of morphological forms. Studies that rely on morphological characteristics to quantify the abundances of all stages of the fungal life cycle face the challenge of correctly identifying and enumerating the nondescript zoospores. These zoospores, however, provide an important trophic link between large colonial phytoplankton and zooplankton: that is, once the carbon is liberated from phytoplankton into the parasitic zoospores, the latter are consumed by zooplankton and carbon is retained in the aquatic food web rather than exported from the system. This study provides a tool to quantify zoospores and evaluate the consumption of zoospores by zooplankton in order to further our understanding of their role in food web dynamics.
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discovery of dark matter Fungi in aquatic ecosystems demands a reappraisal of the phylogeny and ecology of Zoosporic Fungi
Fungal Ecology, 2016Co-Authors: Christian Wurzbacher, Hanspeter Grossart, Timothy Y James, Maiko KagamiAbstract:Our knowledge of Zoosporic fungal phylogeny, physiology, and ecological functions, in particular their role in aquatic food web dynamics and biogeochemistry, is limited. The recent discovery of numerous dark matter Fungi (DMF), i.e., uncultured and poorly known taxa belonging to early diverging branches of the fungal tree (namely the Rozellomycota and Chytridiomycota) calls for reconsideration of the phylogeny and ecology of Zoosporic Fungi. In this opinion paper, we summarize the exploration of new, recently discovered lineages of DMF and their implications for the ecology, evolution, and biogeography of the rapidly growing fungal tree. We also discuss possible ecological roles of Zoosporic Fungi in relation to recent methodological developments including single cell genomics and cultivation efforts. Finally, we suggest linking explorative with experimental research to gain deeper insights into the physiology and ecological functioning of Zoosporic Fungi DMF in aquatic habitats.
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Quantitative methods for the analysis of Zoosporic Fungi.
Journal of Microbiological Methods, 2012Co-Authors: Agostina Marano, Serena Rasconi, Frank H. Gleason, Felix Bärlocher, Carmen L.a Pires-zottarelli, Osu Lilje, Steve K. Schmidt, Maiko Kagami, Marcelo D. Barrera, Télesphore Sime-ngandoAbstract:Quantitative estimations of Zoosporic Fungi in the environment have historically received little attention, primarily due to methodological challenges and their complex life cycles. Conventional methods for quantitative analysis of Zoosporic Fungi to date have mainly relied on direct observation and baiting techniques, with subsequent fungal identification in the laboratory using morphological characteristics. Although these methods are still fundamentally useful, there has been an increasing preference for quantitative microscopic methods based on staining with fluorescent dyes, as well as the use of hybridization probes. More recently however PCR based methods for profiling and quantification (semi- and absolute) have proven to be rapid and accurate diagnostic tools for assessing Zoosporic fungal assemblages in environmental samples. Further application of next generation sequencing technologies will however not only advance our quantitative understanding of Zoosporic fungal ecology, but also their function through the analysis of their genomes and gene expression as resources and databases expand in the future. Nevertheless, it is still necessary to complement these molecular-based approaches with cultivation-based methods in order to gain a fuller quantitative understanding of the ecological and physiological roles of Zoosporic Fungi.
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development of a real time pcr assay for quantitative assessment of uncultured freshwater Zoosporic Fungi
Journal of Microbiological Methods, 2010Co-Authors: Emilie Lefevre, Marlene Jobard, Maiko Kagami, Jeanstephane Venisse, Alexandre Bec, Christian Amblard, Telesphore SimengandoAbstract:Recently, molecular environmental surveys of the eukaryotic microbial community in lakes have revealed a high diversity of sequences belonging to uncultured Zoosporic Fungi. Although they are known as saprobes and algal parasites in freshwater systems, Zoosporic Fungi have been neglected in microbial food web studies. Recently, it has been suggested that Zoosporic Fungi, via the consumption of their zoospores by zooplankters, could transfer energy from large inedible algae and particulate organic material to higher trophic levels. However, because of their small size and their lack of distinctive morphological features, traditional microscopy does not allow the detection of fungal zoospores in the field. Hence, quantitative data on fungal zoospores in natural environments is missing. We have developed a quantitative PCR (qPCR) assay for the quantification of fungal zoospores in lakes. Specific primers were designed and qPCR conditions were optimized using a range of target and non-target plasmids obtained from previous freshwater environmental 18S rDNA surveys. When optimal DNA extraction protocol and qPCR conditions were applied, the qPCR assay developed in this study demonstrated high specificity and sensitivity, with as low as 100 18S rDNA copies per reaction detected. Although the present work focuses on the design and optimization of a new qPCR assay, its application to natural samples indicated that qPCR offers a promising tool for quantitative assessment of fungal zoospores in natural environments. We conclude that this will contribute to a better understanding of the ecological significance of Zoosporic Fungi in microbial food webs of pelagic ecosystems.
Emilie Lefevre - One of the best experts on this subject based on the ideXlab platform.
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temporal variation of the small eukaryotic community in two freshwater lakes emphasis on Zoosporic Fungi
Aquatic Microbial Ecology, 2012Co-Authors: Emilie Lefevre, Peter M. Letcher, Martha J PowellAbstract:Applications of molecular approaches to the study of microbial eukaryotic communities in fresh- water lakes are transforming our understanding of these ecosystems. One of the most unexpected discov- eries is that Zoosporic Fungi significantly dominate the planktonic fungal diversity. Although Zoosporic Fungi are now recognized as an important component of aquatic microbial food webs, our knowledge of their community structure and temporal variability remains poor. The objectives of our study were (1) to compare and describe the contribution of Zoosporic Fungi to the eukaryotic diversity in 2 lakes differing in their trophic status during the mixing and the stratified seasons and (2) to phylogenetically identify the recovered Zoosporic fungal sequences. The small eukaryotes (0.6 to 8 µm) of the euphotic zone of the oligotrophic Lake Tusca - loosa and meso-eutrophic Lake Lurleen (Alabama, USA) were collected over 1 yr. Analyses of the 28S rDNA clone libraries showed that Zoosporic Fungi dom- inated the small planktonic fungal community and were more diverse in the meso-eutrophic lake and dur- ing the thermal stratification. Although the overall structure of the eukaryotic community was similar between the 2 lakes, at lower taxonomic levels, com- munity composition differed. Analyses of the retrieved fungal sequences revealed that Zoosporic Fungi mostly affiliated with Rhizophydiales and Chytri diales or formed environmental clades. Although the phyto- planktonic community was also monitored, Zoosporic fungal parasites were rarely observed on algae. These results provide new insights into the diversity and seasonality of the Zoosporic fungal community in lake ecosystems.
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Hidden diversity among aquatic heterotrophic flagellates: ecological potentials of Zoosporic Fungi
Hydrobiologia, 2011Co-Authors: Télesphore Sime-ngando, Emilie Lefevre, Frank H. GleasonAbstract:Since the emergence of the ‘microbial loop’ concept, heterotrophic flagellates have received particular attention as grazers in aquatic ecosystems. These microbes have historically been regarded incorrectly as a homogeneous group of bacterivorous protists in aquatic systems. More recently, environmental rDNA surveys of small heterotrophic flagellates in the pelagic zone of freshwater ecosystems have provided new insights. (i) The dominant phyla found by molecular studies differed significantly from those known from morphological studies with the light microscope, (ii) the retrieved phylotypes generally belong to well-established eukaryotic clades, but there is a very large diversity within these clades and (iii) a substantial part of the retrieved sequences cannot be assigned to bacterivorous but can be assigned instead to parasitic and saprophytic organisms, such as Zoosporic true Fungi (chytrids), fungus-like organisms (stramenopiles), or virulent alveolate parasites (Perkinsozoa and Amoebophrya sp.). All these microorganisms are able to produce small zoospores to assure dispersal in water during their life-cycles. Based on the existing literature on true Fungi and fungus-like organisms, and on the more recently published eukaryotic rDNA environmental studies and morphological observations, we conclude that previously overlooked microbial diversity and related ecological potentials require intensive investigation (i) for an improved understanding of the roles of heterotrophic flagellates in pelagic ecosystems and (ii) to properly integrate the concept of ‘the microbial loop’ into modern pelagic microbial ecology.
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development of a real time pcr assay for quantitative assessment of uncultured freshwater Zoosporic Fungi
Journal of Microbiological Methods, 2010Co-Authors: Emilie Lefevre, Marlene Jobard, Maiko Kagami, Jeanstephane Venisse, Alexandre Bec, Christian Amblard, Telesphore SimengandoAbstract:Recently, molecular environmental surveys of the eukaryotic microbial community in lakes have revealed a high diversity of sequences belonging to uncultured Zoosporic Fungi. Although they are known as saprobes and algal parasites in freshwater systems, Zoosporic Fungi have been neglected in microbial food web studies. Recently, it has been suggested that Zoosporic Fungi, via the consumption of their zoospores by zooplankters, could transfer energy from large inedible algae and particulate organic material to higher trophic levels. However, because of their small size and their lack of distinctive morphological features, traditional microscopy does not allow the detection of fungal zoospores in the field. Hence, quantitative data on fungal zoospores in natural environments is missing. We have developed a quantitative PCR (qPCR) assay for the quantification of fungal zoospores in lakes. Specific primers were designed and qPCR conditions were optimized using a range of target and non-target plasmids obtained from previous freshwater environmental 18S rDNA surveys. When optimal DNA extraction protocol and qPCR conditions were applied, the qPCR assay developed in this study demonstrated high specificity and sensitivity, with as low as 100 18S rDNA copies per reaction detected. Although the present work focuses on the design and optimization of a new qPCR assay, its application to natural samples indicated that qPCR offers a promising tool for quantitative assessment of fungal zoospores in natural environments. We conclude that this will contribute to a better understanding of the ecological significance of Zoosporic Fungi in microbial food webs of pelagic ecosystems.
