@article{VandenWyngaertRojasJimenezSetoetal.2018, author = {Van den Wyngaert, Silke and Rojas-Jimenez, Keilor and Seto, Kensuke and Kagami, Maiko and Grossart, Hans-Peter}, title = {Diversity and Hidden Host Specificity of Chytrids Infecting Colonial Volvocacean Algae}, series = {Journal of Eukaryotic Microbiology}, volume = {65}, journal = {Journal of Eukaryotic Microbiology}, number = {6}, publisher = {Wiley}, address = {Hoboken}, issn = {1066-5234}, doi = {10.1111/jeu.12632}, pages = {870 -- 881}, year = {2018}, abstract = {Chytrids are zoosporic fungi that play an important, but yet understudied, ecological role in aquatic ecosystems. Many chytrid species have been morphologically described as parasites on phytoplankton. However, the majority of them have rarely been isolated and lack DNA sequence data. In this study we isolated and cultivated three parasitic chytrids, infecting a common volvocacean host species, Yamagishiella unicocca. To identify the chytrids, we characterized morphology and life cycle, and analyzed phylogenetic relationships based on 18S and 28S rDNA genes. Host range and specificity of the chytrids was determined by cross-infection assays with host strains, characterized by rbcL and ITS markers. We were able to confirm the identity of two chytrid strains as Endocoenobium eudorinae Ingold and Dangeardia mamillata Schroder and described the third chytrid strain as Algomyces stechlinensis gen. et sp. nov. The three chytrids were assigned to novel and phylogenetically distant clades within the phylum Chytridiomycota, each exhibiting different host specificities. By integrating morphological and molecular data of both the parasitic chytrids and their respective host species, we unveiled cryptic host-parasite associations. This study highlights that a high prevalence of (pseudo)cryptic diversity requires molecular characterization of both phytoplankton host and parasitic chytrid to accurately identify and compare host range and specificity, and to study phytoplankton-chytrid interactions in general.}, language = {en} } @misc{GrossartRojasJimenez2016, author = {Großart, Hans-Peter and Rojas-Jimenez, Keilor}, title = {Aquatic fungi: targeting the forgotten in microbial ecology}, series = {Current opinion in microbiology}, volume = {31}, journal = {Current opinion in microbiology}, publisher = {Elsevier}, address = {London}, issn = {1369-5274}, doi = {10.1016/j.mib.2016.03.016}, pages = {140 -- 145}, year = {2016}, abstract = {Fungi constitute important and conspicuous components of aquatic microbial communities, but their diversity and functional roles remain poorly characterized. New methods and conceptual frameworks are required to accurately describe their ecological roles, involvement in global cycling processes, and utility for human activities, considering both cultivation independent techniques as well as experiments in laboratory and in natural ecosystems. Here we highlight recent developments and extant knowledge gaps in aquatic mycology, and provide a conceptual model to expose the importance of fungi in aquatic food webs and related biogeochemical processes.}, language = {en} } @article{RojasJimenezGrossartCordesetal.2020, author = {Rojas-Jimenez, Keilor and Grossart, Hans-Peter and Cordes, Erik and Cort{\´e}s, Jorge}, title = {Fungal Communities in Sediments Along a Depth Gradient in the Eastern Tropical Pacific}, series = {Frontiers in Microbiology}, volume = {11}, journal = {Frontiers in Microbiology}, publisher = {Frontiers Media}, address = {Lausanne}, issn = {1664-302X}, doi = {10.3389/fmicb.2020.575207}, pages = {9}, year = {2020}, abstract = {Deep waters represent the largest biome on Earth and the largest ecosystem of Costa Rica. Fungi play a fundamental role in global biogeochemical cycling in marine sediments, yet, they remain little explored. We studied fungal diversity and community composition in several marine sediments from 16 locations sampled along a bathymetric gradient (from a depth of 380 to 3,474 m) in two transects of about 1,500 km length in the Eastern Tropical Pacific (ETP) of Costa Rica. Sequence analysis of the V7-V8 region of the 18S rRNA gene obtained from sediment cores revealed the presence of 787 fungal amplicon sequence variants (ASVs). On average, we detected a richness of 75 fungal ASVs per sample. Ascomycota represented the most abundant phylum with Saccharomycetes constituting the dominant class. Three ASVs accounted for ca. 63\% of all fungal sequences: the yeast Metschnikowia (49.4\%), Rhizophydium (6.9\%), and Cladosporium (6.7\%). We distinguished a cluster composed mainly by yeasts, and a second cluster by filamentous fungi, but we were unable to detect a strong effect of depth and the overlying water temperature, salinity, dissolved oxygen (DO), and pH on the composition of fungal communities. We highlight the need to understand further the ecological role of fungi in deep-sea ecosystems.}, language = {en} } @misc{FrenkenAlacidBergeretal.2017, author = {Frenken, Thijs and Alacid, Elisabet and Berger, Stella A. and Bourne, Elizabeth Charlotte and Gerphagnon, Melanie and Großart, Hans-Peter and Gsell, Alena S. and Ibelings, Bas W. and Kagami, Maiko and Kupper, Frithjof C. and Letcher, Peter M. and Loyau, Adeline and Miki, Takeshi and Nejstgaard, Jens C. and Rasconi, Serena and Rene, Albert and Rohrlack, Thomas and Rojas-Jimenez, Keilor and Schmeller, Dirk S. and Scholz, Bettina and Seto, Kensuke and Sime-Ngando, Telesphore and Sukenik, Assaf and Van de Waal, Dedmer B. and Van den Wyngaert, Silke and Van Donk, Ellen and Wolinska, Justyna and Wurzbacher, Christian and Agha, Ramsy}, title = {Integrating chytrid fungal parasites into plankton ecology: research gaps and needs}, series = {Environmental microbiology}, volume = {19}, journal = {Environmental microbiology}, publisher = {Wiley}, address = {Hoboken}, issn = {1462-2912}, doi = {10.1111/1462-2920.13827}, pages = {3802 -- 3822}, year = {2017}, abstract = {Chytridiomycota, often referred to as chytrids, can be virulent parasites with the potential to inflict mass mortalities on hosts, causing e.g. changes in phytoplankton size distributions and succession, and the delay or suppression of bloom events. Molecular environmental surveys have revealed an unexpectedly large diversity of chytrids across a wide range of aquatic ecosystems worldwide. As a result, scientific interest towards fungal parasites of phytoplankton has been gaining momentum in the past few years. Yet, we still know little about the ecology of chytrids, their life cycles, phylogeny, host specificity and range. Information on the contribution of chytrids to trophic interactions, as well as co-evolutionary feedbacks of fungal parasitism on host populations is also limited. This paper synthesizes ideas stressing the multifaceted biological relevance of phytoplankton chytridiomycosis, resulting from discussions among an international team of chytrid researchers. It presents our view on the most pressing research needs for promoting the integration of chytrid fungi into aquatic ecology.}, language = {en} } @article{RojasJimenezWurzbacherBourneetal.2017, author = {Rojas-Jimenez, Keilor and Wurzbacher, Christian and Bourne, Elizabeth Charlotte and Chiuchiolo, Amy and Priscu, John C. and Grossart, Hans-Peter}, title = {Early diverging lineages within Cryptomycota and Chytridiomycota dominate the fungal communities in ice-covered lakes of the McMurdo Dry Valleys, Antarctica}, series = {Scientific reports}, volume = {7}, journal = {Scientific reports}, publisher = {Nature Publ. Group}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-017-15598-w}, pages = {11}, year = {2017}, abstract = {Antarctic ice-covered lakes are exceptional sites for studying the ecology of aquatic fungi under conditions of minimal human disturbance. In this study, we explored the diversity and community composition of fungi in five permanently covered lake basins located in the Taylor and Miers Valleys of Antarctica. Based on analysis of the 18S rRNA sequences, we showed that fungal taxa represented between 0.93\% and 60.32\% of the eukaryotic sequences. Cryptomycota and Chytridiomycota dominated the fungal communities in all lakes; however, members of Ascomycota, Basidiomycota, Zygomycota, and Blastocladiomycota were also present. Of the 1313 fungal OTUs identified, the two most abundant, belonging to LKM11 and Chytridiaceae, comprised 74\% of the sequences. Significant differences in the community structure were determined among lakes, water depths, habitat features (i.e., brackish vs. freshwaters), and nucleic acids (DNA vs. RNA), suggesting niche differentiation. Network analysis suggested the existence of strong relationships among specific fungal phylotypes as well as between fungi and other eukaryotes. This study sheds light on the biology and ecology of basal fungi in aquatic systems. To our knowledge, this is the first report showing the predominance of early diverging lineages of fungi in pristine limnetic ecosystems, particularly of the enigmatic phylum Cryptomycota.}, language = {en} } @article{PerkinsGanzertRojasJimenezetal.2019, author = {Perkins, Anita K. and Ganzert, Lars and Rojas-Jimenez, Keilor and Fonvielle, Jeremy Andre and Hose, Grant C. and Grossart, Hans-Peter}, title = {Highly diverse fungal communities in carbon-rich aquifers of two contrasting lakes in Northeast Germany}, series = {Fungal ecology}, volume = {41}, journal = {Fungal ecology}, publisher = {Elsevier}, address = {Oxford}, issn = {1754-5048}, doi = {10.1016/j.funeco.2019.04.004}, pages = {116 -- 125}, year = {2019}, abstract = {Fungi are an important component of microbial communities and are well known for their ability to decompose refractory, highly polymeric organic matter. In soils and aquatic systems, fungi play an important role in carbon processing, however, their diversity, community structure and function as well as ecological role, particularly in groundwater, are poorly studied. The aim of this study was to examine the fungal community composition, diversity and function in groundwater from 16 boreholes located in the vicinity of two lakes in NE Germany that are characterized by contrasting trophic status. The analysis of 28S rRNA gene sequences amplified from the groundwater revealed high fungal diversity arid clear differences in community structure between the aquifers. Most sequences were assigned to Ascomycota and Basidiomycota, but members of Chytridiomycota, Cryptomycota, Zygomycota, Blastocladiomycota, Glomeromycota and Neocallimastigomycota were also detected. In addition, 27 species of fungi were successfully isolated from the groundwater samples and tested for their ability to decompose complex organic polymers - the predominant carbon source in the groundwater. Most isolates showed positive activities for at least one of the tested polymer types, with three strains, belonging to the genera Gibberella, Isaria and Cadophora, able to decompose all tested substrates. Our results highlight the high diversity of fungi in groundwater, and point to their important ecological role in breaking down highly polymeric organic matter in these isolated microbial habitats. (C) 2019 Elsevier Ltd and British Mycological Society. All rights reserved.}, language = {en} } @article{PerkinsRoseGrossartetal.2021, author = {Perkins, Anita and Rose, Andrew and Grossart, Hans-Peter and Rojas-Jimenez, Keilor Osvaldo and Barroso Prescott, Selva Kiri and Oakes, Joanne M.}, title = {Oxic and Anoxic Organic Polymer Degradation Potential of Endophytic Fungi From the Marine Macroalga, Ecklonia radiata}, series = {Frontiers in Microbiology}, volume = {12}, journal = {Frontiers in Microbiology}, publisher = {Frontiers in microbiology}, address = {Lausanne, Schweiz}, issn = {1664-302X}, doi = {10.3389/fmicb.2021.726138}, pages = {1 -- 13}, year = {2021}, abstract = {Cellulose and chitin are the most abundant polymeric, organic carbon source globally. Thus, microbes degrading these polymers significantly influence global carbon cycling and greenhouse gas production. Fungi are recognized as important for cellulose decomposition in terrestrial environments, but are far less studied in marine environments, where bacterial organic matter degradation pathways tend to receive more attention. In this study, we investigated the potential of fungi to degrade kelp detritus, which is a major source of cellulose in marine systems. Given that kelp detritus can be transported considerable distances in the marine environment, we were specifically interested in the capability of endophytic fungi, which are transported with detritus, to ultimately contribute to kelp detritus degradation. We isolated 10 species and two strains of endophytic fungi from the kelp Ecklonia radiata. We then used a dye decolorization assay to assess their ability to degrade organic polymers (lignin, cellulose, and hemicellulose) under both oxic and anoxic conditions and compared their degradation ability with common terrestrial fungi. Under oxic conditions, there was evidence that Ascomycota isolates produced cellulose-degrading extracellular enzymes (associated with manganese peroxidase and sulfur-containing lignin peroxidase), while Mucoromycota isolates appeared to produce both lignin and cellulose-degrading extracellular enzymes, and all Basidiomycota isolates produced lignin-degrading enzymes (associated with laccase and lignin peroxidase). Under anoxic conditions, only three kelp endophytes degraded cellulose. We concluded that kelp fungal endophytes can contribute to cellulose degradation in both oxic and anoxic environments. Thus, endophytic kelp fungi may play a significant role in marine carbon cycling via polymeric organic matter degradation.}, language = {en} } @article{KettnerRojasJimenezOberbeckmannetal.2017, author = {Kettner, Marie Therese and Rojas-Jimenez, Keilor and Oberbeckmann, Sonja and Labrenz, Matthias and Großart, Hans-Peter}, title = {Microplastics alter composition of fungal communities in aquatic ecosystems}, series = {Environmental microbiology}, volume = {19}, journal = {Environmental microbiology}, publisher = {Wiley}, address = {Hoboken}, issn = {1462-2912}, doi = {10.1111/1462-2920.13891}, pages = {4447 -- 4459}, year = {2017}, abstract = {Despite increasing concerns about microplastic (MP) pollution in aquatic ecosystems, there is insufficient knowledge on how MP affect fungal communities. In this study, we explored the diversity and community composition of fungi attached to polyethylene (PE) and polystyrene (PS) particles incubated in different aquatic systems in north-east Germany: the Baltic Sea, the River Warnow and a wastewater treatment plant. Based on next generation 18S rRNA gene sequencing, 347 different operational taxonomic units assigned to 81 fungal taxa were identified on PE and PS. The MP-associated communities were distinct from fungal communities in the surrounding water and on the natural substrate wood. They also differed significantly among sampling locations, pointing towards a substrate and location specific fungal colonization. Members of Chytridiomycota, Cryptomycota and Ascomycota dominated the fungal assemblages, suggesting that both parasitic and saprophytic fungi thrive in MP biofilms. Thus, considering the worldwide increasing accumulation of plastic particles as well as the substantial vector potential of MP, especially these fungal taxa might benefit from MP pollution in the aquatic environment with yet unknown impacts on their worldwide distribution, as well as biodiversity and food web dynamics at large.}, language = {en} } @misc{RojasJimenezRieckWurzbacheretal.2019, author = {Rojas-Jimenez, Keilor and Rieck, Angelika and Wurzbacher, Christian and J{\"u}rgens, Klaus and Labrenz, Matthias and Grossart, Hans-Peter}, title = {A Salinity Threshold Separating Fungal Communities in the Baltic Sea}, series = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, number = {739}, issn = {1866-8372}, doi = {10.25932/publishup-43493}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-434937}, pages = {9}, year = {2019}, abstract = {Salinity is a significant factor for structuring microbial communities, but little is known for aquatic fungi, particularly in the pelagic zone of brackish ecosystems. In this study, we explored the diversity and composition of fungal communities following a progressive salinity decline (from 34 to 3 PSU) along three transects of ca. 2000 km in the Baltic Sea, the world's largest estuary. Based on 18S rRNA gene sequence analysis, we detected clear changes in fungal community composition along the salinity gradient and found significant differences in composition of fungal communities established above and below a critical value of 8 PSU. At salinities below this threshold, fungal communities resembled those from freshwater environments, with a greater abundance of Chytridiomycota, particularly of the orders Rhizophydiales, Lobulomycetales, and Gromochytriales. At salinities above 8 PSU, communities were more similar to those from marine environments and, depending on the season, were dominated by a strain of the LKM11 group (Cryptomycota) or by members of Ascomycota and Basidiomycota. Our results highlight salinity as an important environmental driver also for pelagic fungi, and thus should be taken into account to better understand fungal diversity and ecological function in the aquatic realm.}, language = {en} } @article{AriasAndresKluemperRojasJimenezetal.2018, author = {Arias-Andres, Maria and Kluemper, Uli and Rojas-Jimenez, Keilor and Grossart, Hans-Peter}, title = {Microplastic pollution increases gene exchange in aquatic ecosystems}, series = {Environmental pollution}, volume = {237}, journal = {Environmental pollution}, publisher = {Elsevier}, address = {Oxford}, issn = {0269-7491}, doi = {10.1016/j.envpol.2018.02.058}, pages = {253 -- 261}, year = {2018}, abstract = {Pollution by microplastics in aquatic ecosystems is accumulating at an unprecedented scale, emerging as a new surface for biofilm formation and gene exchange. In this study, we determined the permissiveness of aquatic bacteria towards a model antibiotic resistance plasmid, comparing communities that form biofilms on microplastics vs. those that are free-living. We used an exogenous and red-fluorescent E. coli donor strain to introduce the green-fluorescent broad-host-range plasmid pKJKS which encodes for trimethoprim resistance. We demonstrate an increased frequency of plasmid transfer in bacteria associated with microplastics compared to bacteria that are free-living or in natural aggregates. Moreover, comparison of communities grown on polycarbonate filters showed that increased gene exchange occurs in a broad range of phylogenetically-diverse bacteria. Our results indicate horizontal gene transfer in this habitat could distinctly affect the ecology of aquatic microbial communities on a global scale. The spread of antibiotic resistance through microplastics could also have profound consequences for the evolution of aquatic bacteria and poses a neglected hazard for human health.}, language = {en} }