@phdthesis{Wurzbacher2012, author = {Wurzbacher, Christian}, title = {Ecological function and biodiversity of aquatic fungi in lentic freshwater systems}, address = {Potsdam}, pages = {131 S.}, year = {2012}, 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} } @misc{WurzbacherFuchsAttermeyeretal.2017, author = {Wurzbacher, Christian and Fuchs, Andrea and Attermeyer, Katrin and Frindte, Katharina and Grossart, Hans-Peter and Hupfer, Michael and Casper, Peter and Monaghan, Michael T.}, title = {Shifts among Eukaryota, Bacteria, and Archaea define the vertical organization of a lake sediment}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1111}, issn = {1866-8372}, doi = {10.25932/publishup-43196}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-431965}, pages = {18}, year = {2017}, abstract = {Background Lake sediments harbor diverse microbial communities that cycle carbon and nutrients while being constantly colonized and potentially buried by organic matter sinking from the water column. The interaction of activity and burial remained largely unexplored in aquatic sediments. We aimed to relate taxonomic composition to sediment biogeochemical parameters, test whether community turnover with depth resulted from taxonomic replacement or from richness effects, and to provide a basic model for the vertical community structure in sediments. Methods We analyzed four replicate sediment cores taken from 30-m depth in oligo-mesotrophic Lake Stechlin in northern Germany. Each 30-cm core spanned ca. 170 years of sediment accumulation according to 137Cs dating and was sectioned into layers 1-4 cm thick. We examined a full suite of biogeochemical parameters and used DNA metabarcoding to examine community composition of microbial Archaea, Bacteria, and Eukaryota. Results Community β-diversity indicated nearly complete turnover within the uppermost 30 cm. We observed a pronounced shift from Eukaryota- and Bacteria-dominated upper layers (<5 cm) to Bacteria-dominated intermediate layers (5-14 cm) and to deep layers (>14 cm) dominated by enigmatic Archaea that typically occur in deep-sea sediments. Taxonomic replacement was the prevalent mechanism in structuring the community composition and was linked to parameters indicative of microbial activity (e.g., CO2 and CH4 concentration, bacterial protein production). Richness loss played a lesser role but was linked to conservative parameters (e.g., C, N, P) indicative of past conditions. Conclusions By including all three domains, we were able to directly link the exponential decay of eukaryotes with the active sediment microbial community. The dominance of Archaea in deeper layers confirms earlier findings from marine systems and establishes freshwater sediments as a potential low-energy environment, similar to deep sea sediments. We propose a general model of sediment structure and function based on microbial characteristics and burial processes. An upper "replacement horizon" is dominated by rapid taxonomic turnover with depth, high microbial activity, and biotic interactions. A lower "depauperate horizon" is characterized by low taxonomic richness, more stable "low-energy" conditions, and a dominance of enigmatic Archaea.}, language = {en} } @article{WurzbacherFuchsAttermeyeretal.2017, author = {Wurzbacher, Christian and Fuchs, Andrea and Attermeyer, Katrin and Frindte, Katharina and Grossart, Hans-Peter and Hupfer, Michael and Casper, Peter and Monaghan, Michael T.}, title = {Shifts among Eukaryota, Bacteria, and Archaea define the vertical organization of a lake sediment}, series = {Microbiome}, volume = {5}, journal = {Microbiome}, publisher = {BioMed Central}, address = {London}, issn = {2049-2618}, doi = {10.1186/s40168-017-0255-9}, pages = {16}, year = {2017}, abstract = {Background: Lake sediments harbor diverse microbial communities that cycle carbon and nutrients while being constantly colonized and potentially buried by organic matter sinking from the water column. The interaction of activity and burial remained largely unexplored in aquatic sediments. We aimed to relate taxonomic composition to sediment biogeochemical parameters, test whether community turnover with depth resulted from taxonomic replacement or from richness effects, and to provide a basic model for the vertical community structure in sediments. Methods: We analyzed four replicate sediment cores taken from 30-m depth in oligo-mesotrophic Lake Stechlin in northern Germany. Each 30-cm core spanned ca. 170 years of sediment accumulation according to Cs-137 dating and was sectioned into layers 1-4 cm thick. We examined a full suite of biogeochemical parameters and used DNA metabarcoding to examine community composition of microbial Archaea, Bacteria, and Eukaryota. Results: Community beta-diversity indicated nearly complete turnover within the uppermost 30 cm. We observed a pronounced shift from Eukaryota- and Bacteria-dominated upper layers (<5 cm) to Bacteria-dominated intermediate layers (5-14 cm) and to deep layers (>14 cm) dominated by enigmatic Archaea that typically occur in deep-sea sediments. Taxonomic replacement was the prevalent mechanism in structuring the community composition and was linked to parameters indicative of microbial activity (e.g., CO2 and CH4 concentration, bacterial protein production). Richness loss played a lesser role but was linked to conservative parameters (e.g., C, N, P) indicative of past conditions. Conclusions: By including all three domains, we were able to directly link the exponential decay of eukaryotes with the active sediment microbial community. The dominance of Archaea in deeper layers confirms earlier findings from marine systems and establishes freshwater sediments as a potential low-energy environment, similar to deep sea sediments. We propose a general model of sediment structure and function based on microbial characteristics and burial processes. An upper "replacement horizon" is dominated by rapid taxonomic turnover with depth, high microbial activity, and biotic interactions. A lower "depauperate horizon" is characterized by low taxonomic richness, more stable "low-energy" conditions, and a dominance of enigmatic Archaea.}, language = {en} } @article{WurzbacherRoeselRychlaetal.2014, author = {Wurzbacher, Christian and Roesel, Stefan and Rychla, Anna and Grossart, Hans-Peter}, title = {Importance of saprotrophic freshwater fungi for pollen degradation}, series = {PLoS one}, volume = {9}, journal = {PLoS one}, number = {4}, publisher = {PLoS}, address = {San Fransisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0094643}, pages = {12}, year = {2014}, abstract = {Fungi and bacteria are the major organic matter (OM) decomposers in aquatic ecosystems. While bacteria are regarded as primary mineralizers in the pelagic zone of lakes and oceans, fungi dominate OM decomposition in streams and wetlands. Recent findings indicate that fungal communities are also active in lakes, but little is known about their diversity and interactions with bacteria. Therefore, the decomposer niche overlap of saprotrophic fungi and bacteria was studied on pollen (as a seasonally recurring source of fine particulate OM) by performing microcosm experiments with three different lake types. Special emphasis was placed on analysis of fungal community composition and diversity. We hypothesized that (I) pollen select for small saprotrophic fungi and at the same time for typical particle-associated bacteria; (II) fungal communities form specific free-living and attached sub-communities in each lake type; (III) the ratio between fungi or bacteria on pollen is controlled by the lake's chemistry. Bacteria-to-fungi ratios were determined by quantitative PCR (qPCR), and bacterial and fungal diversity were studied by clone libraries and denaturing gradient gel electrophoresis (DGGE) fingerprints. A protease assay was used to identify functional differences between treatments. For generalization, systematic differences in bacteria-to-fungi ratios were analyzed with a dataset from the nearby Baltic Sea rivers. High abundances of Chytridiomycota as well as occurrences of Cryptomycota and yeast-like fungi confirm the decomposer niche overlap of saprotrophic fungi and bacteria on pollen. As hypothesized, microbial communities consistently differed between the lake types and exhibited functional differences. Bacteria-to-fungi ratios correlated well with parameters such as organic carbon and pH. The importance of dissolved organic carbon and nitrogen for bacteria-to-fungi ratios was supported by the Baltic Sea river dataset. Our findings highlight the fact that carbon-to-nitrogen ratios may also control fungal contributions to OM decomposition in aquatic ecosystems.}, 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} } @misc{GarciaBuckHamiltonetal.2018, author = {Garcia, Sarahi L. and Buck, Moritz and Hamilton, Joshua J. and Wurzbacher, Christian and Grossart, Hans-Peter and McMahon, Katherine D. and Eiler, Alexander}, title = {Model communities hint at promiscuous metabolic linkages between ubiquitous free-living freshwater bacteria}, series = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, number = {714}, doi = {10.25932/publishup-42729}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-427299}, pages = {8}, year = {2018}, abstract = {Genome streamlining is frequently observed in free-living aquatic microorganisms and results in physiological dependencies between microorganisms. However, we know little about the specificity of these microbial associations. In order to examine the specificity and extent of these associations, we established mixed cultures from three different freshwater environments and analyzed the cooccurrence of organisms using a metagenomic time series. Free-living microorganisms with streamlined genomes lacking multiple biosynthetic pathways showed no clear recurring pattern in their interaction partners. Free-living freshwater bacteria form promiscuous cooperative associations. This notion contrasts with the well-documented high specificities of interaction partners in host-associated bacteria. Considering all data together, we suggest that highly abundant free-living bacterial lineages are functionally versatile in their interactions despite their distinct streamlining tendencies at the single-cell level. This metabolic versatility facilitates interactions with a variable set of community members.}, language = {en} } @article{SalkaWurzbacherGarciaetal.2014, author = {Salka, Ivette and Wurzbacher, Christian and Garcia, Sarahi L. and Labrenz, Matthias and Juergens, Klaus and Grossart, Hans-Peter}, title = {Distribution of acI-Actinorhodopsin genes in Baltic Sea salinity gradients indicates adaptation of facultative freshwater photoheterotrophs to brackish waters}, series = {Environmental microbiology}, volume = {16}, journal = {Environmental microbiology}, number = {2}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1462-2912}, pages = {586 -- 597}, year = {2014}, language = {en} } @article{WurzbacherSalkaGrossart2012, author = {Wurzbacher, Christian and Salka, Ivette and Grossart, Hans-Peter}, title = {Environmental actinorhodopsin expression revealed by a new in situ filtration and fixation sampler}, series = {Environmental microbiology reports}, volume = {4}, journal = {Environmental microbiology reports}, number = {5}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1758-2229}, doi = {10.1111/j.1758-2229.2012.00350.x}, pages = {491 -- 497}, year = {2012}, abstract = {Freshwater Actinobacteria are an important and dominant group of bacterioplankton in most temperate freshwater systems. Recently, metagenomic studies discovered rhodopsin-like protein-coding sequences present in Actinobacteria which could be a decisive hint for their success in freshwater ecosystems. We analysed the diversity of actinorhodopsin (ActR) in Lake Stechlin (northern Germany) and assessed the actR expression profile during a diurnal cycle. We obtained 85 positive actR clones which could be subsequently grouped to 17 operational taxonomic units assuming a 90\% sequence similarity. The phylogenetic analysis points to a close relationship of all obtained sequences to the acI lineage of Actinobacteria, forming six independent clusters. For the first time, we followed in situ transcription of actR in Lake Stechlin revealing a rather constitutive circadian gene expression. For analysing in situ expression patterns of functional genes in aquatic ecosystems, such as actR, we invented a new in situ filtration and fixation sampler (IFFS). The IFFS enables the representative investigation of microbial transcriptomes in any aquatic ecosystem at all water depths. The IFFS sampler is simple and inexpensive, and we provide all engineering plans for an easy rebuild. Consequently, our IFFS is suitable to reliably study expression of any known functional gene of any aquatic microorganism.}, language = {en} }