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Jens Boenigk - One of the best experts on this subject based on the ideXlab platform.
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Potential toxicity of chrysophytes affiliated with Poterioochromonas and related ‘Spumella-like ’ flagellates
2016Co-Authors: Jens Boenigk, Peter StadlerAbstract:The chrysophyte genera Poterioochromonas and Ochromonas and their heterotrophic analogons, i.e. the ‘Spumella-like ’ flagellates, account for a significant and often dominating fraction of the pelagic nanoplankton. Even though several osmotrophically and autotrophically grown strains of Ochromonas and Poterioochromonas are assumed to produce toxins, the potential toxicity has been investigated neither for its association with bacterivorous nutrition nor within the related exclusively heterotrophic ‘Spumella-like ’ flagellates. We investigated the toxic potential of several flagellate strains using cultures of flagellates, cell extracts and filtrate of flagellate cultures. The effect on potential predators was exemplarily tested for the cladoceran Daphnia magna and the rotifer Platyias sp. All tested heterotrophic and mixotrophic flagellate strains were toxic to zooplankton at abundances exceeding 104 flagellates mL1. For the rotifers, survival on any of the flagellate strains was significantly lower than that in the control treatment (P < 0.001) already after 24 h. We conclude that (i) ‘Spumella-like ’ flagellates can be toxic to zooplankton, (ii) all tested flagellates, i.e. heterotrophic and mixotrophic flagellates, feeding phagotrophi-cally can be toxic to zooplankton and (iii) sublethal effects may be observed at typical field abundances, even though acute toxicity seems to be restricted to flagellate abundances observed only at peak events
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Small but Manifold - Hidden Diversity in "Spumella-like Flagellates".
2016Co-Authors: Lars Grossmann, Christina Bock, Michael Schweikert, Jens BoenigkAbstract:Colourless, nonscaled chrysophytes comprise morphologically similar or even indistinguishable flagellates which are important bacterivors in water and soil crucial for ecosystem functioning. However, phylogenetic analyses indicate a multiple origin of such colourless, nonscaled flagellate lineages. These flagellates are often referred to as "Spumella-like flagellates" in ecological and biogeographic studies. Although this denomination reflects an assumed polyphyly, it obscures the phylogenetic and taxonomic diversity of this important flagellate group and, thus, hinders progress in lineage- and taxon-specific ecological surveys. The smallest representatives of colourless chrysophytes have been addressed in very few taxonomic studies although they are among the dominant flagellates in field communities. To overcome the blurred picture and set the field for further investigation in biogeography and ecology of the organisms in question, we studied a set of strains of specifically small, colourless, nonscaled chrysomonad flagellates by means of electron microscopy and molecular analyses. They were isolated by a filtration-acclimatisation approach focusing on flagellates of around 5 μm. We present the phylogenetic position of eight different lineages on both the ordinal and the generic level. Accordingly, we describe the new genera ApoikioSpumella, ChromulinoSpumella, SegregatoSpumella, CornoSpumella and AcriSpumella Boenigk et Grossmann n. g. and different species within them.
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taxonomic and ecological characterization of stomatocysts of Spumella like flagellates chrysophyceae 1
2010Co-Authors: Barbara M Findenig, Antonis Chatzinotas, Jens BoenigkAbstract:Cyst formation is a characteristic feature of chrysophytes. Cyst morphology is used for species identification, and the distribution of cysts in sediment cores is used to infer past climate conditions. The affiliation of stomatocyst demes with morphospecies, however, remains unclear. Here, we investigated the taxonomic and ecological value of the occurrence of cyst formation and cyst morphology to differentiate chrysophyte flagellates of the Spumella-morphodeme, which are among the numerically dominant eukaryotes in many aquatic and terrestrial habitats. In the investigated 90 strains of Spumella-like flagellates, we observed encystment only in six strains despite the broad range of temperature regimes and chemical factors tested. Spumella-like flagellates that produce cysts are affiliated with different subclusters within the Chrysophyceae and are closely related to strains for which cyst formation is not known. The occurrence of cyst formation is therefore unsuitable as a taxonomic criterion. Cyst morphology allows for differentiating some strains even though distinctly different strains may have similar or even identical-looking cyst demes. Despite considerable changes in cell size of the vegetative cells related to the nutritional status, the size of the cysts was always larger than that of a typical vegetative cell. Cysts were colorless and had no chromatophores, and some granula were visible in the light microscope. None of the investigated strains and none of the so far published cyst descriptions of Spumella spp. entirely seem to match the cyst description of the generic type strain. However, taking methodological bias between light and electron microscopical investigations into account, the cysts 199hm (this paper) and N1846 (Yubuki et al. 2008) seem to correspond to the cyst of the generic type strain. We propose the strain 199hm as epitype for Spumella vulgaris Cienkowsky; we further describe Spumella rivalis Boenigk et Findenig sp. nov., PedoSpumella encystans Boenigk et Findenig gen. et sp. nov., and PoterioSpumella lacustris Boenigk et Findenig gen. et sp. nov.
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SSU rRNA gene variation resolves population heterogeneity and ecophysiological differentiation within a morphospecies (Stramenopiles, Chrysophyceae)
2009Co-Authors: Karin Pfandl, Antonis Chatzinotas, Patricia Dyal, Jens BoenigkAbstract:The objective of this study was to analyze the extent of ecophysiological and molecular homogeneity, or heterogeneity, of distinct protist populations and to test for correlations between molecular distance and ecophysiological adaptation in a widespread and ubiquitous protistan taxon. We selected heterotrophic nanoflagellates of the Spumella morphotype as a model organism, because these flagellates are widespread and among the dominant bacterivores in many microbial communities. We investigated the molecular microdiversity and the ecophysiological tolerances for a total of 13 strains originating from two freshwater samples. We further investigated the affiliation of different ecotypes with distinct small subunit ribosomal ribonucleic acid (SSU rRNA) genotypes, or molecular operational taxonomic units. These regional population studies were further compared to the molecular and ecophysiological diversity of 28 strains originating from remote sampling sites. None of the investigated populations are homogenous, but are rather heterogeneously composed of different ecotypes and genotypes, possibly corresponding to cryptic species. This population heterogeneity may partly explain the deviations between studies on single strains and populations in both laboratory and field studies. The molecular distance between the strains was correlated with the salinity and temperature adaptation of the respective strains, contradicting the assumption that SSU rRNA variation reflects accumulated neutral mutations. Independent of whether this correlation reflects adaptation above the (biological) species level or variation between asexually reproducing lineages, we demonstrate the unsuitability of the current classification system (species concept) for the investigated organisms, at least with respect to ecological and ecophysiological investigations.
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multigene phylogenies of clonal Spumella like strains a cryptic heterotrophic nanoflagellate isolated from different geographical regions
2008Co-Authors: Thorsten Stoeck, Steffen Jost, Jens BoenigkAbstract:Many nanoflagellate morphospecies comprise an enormous variation of genotypes, probably indicating cryptic species. One of the best-investigated morphospecies with respect to molecular and ecophysiological variation are flagellates of the Spumella morphotype. Here, we have phylogenetically analysed three protein-coding genes (actin, alpha-tubulin, beta-tubulin), internal transcribed spacers (ITS1, ITS2) and the 5.8S rDNA of 17 Spumella-like strains isolated from soil, freshwater and marine samples in order to (i) test the validity of the current Spumella-like phylogenetic classification system based exclusively on small subunit (SSU) rDNA, (ii) elucidate the phylogenetic associations of SSU rDNA-unresolved strains and (iii) evaluate the validity of the assignment of ecophysiological adaptations to previously identified SSU rDNA sequence clades. All single-gene analyses show different patterns of support, are incongruent and identify a number of conflicting nodes. Likewise, a concatenation of all protein genes fails to recover specific SSU rDNA clades. However, a combined analysis of all genes confidently resolved the conflicts of the single genes and the protein-gene concatenations and resulted in a tree topology that is identical to the SSU rDNA analysis, but with enhanced phylogenetic resolution and decisively greater support. We conclude that, depending on the genes concatenated, a ‘supergene’ analysis minimizes artefactual effects of single genes and may be superior in its performance in phylogenetically analysing cryptic species. We confirm the validity of the SSU rDNA Spumella-like phyloclades and support the suggestion that these clades indeed seem to reflect certain ecophysiological adaptations.
Karin Pfandl - One of the best experts on this subject based on the ideXlab platform.
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SSU rRNA gene variation resolves population heterogeneity and ecophysiological differentiation within a morphospecies (Stramenopiles, Chrysophyceae)
2009Co-Authors: Karin Pfandl, Antonis Chatzinotas, Patricia Dyal, Jens BoenigkAbstract:The objective of this study was to analyze the extent of ecophysiological and molecular homogeneity, or heterogeneity, of distinct protist populations and to test for correlations between molecular distance and ecophysiological adaptation in a widespread and ubiquitous protistan taxon. We selected heterotrophic nanoflagellates of the Spumella morphotype as a model organism, because these flagellates are widespread and among the dominant bacterivores in many microbial communities. We investigated the molecular microdiversity and the ecophysiological tolerances for a total of 13 strains originating from two freshwater samples. We further investigated the affiliation of different ecotypes with distinct small subunit ribosomal ribonucleic acid (SSU rRNA) genotypes, or molecular operational taxonomic units. These regional population studies were further compared to the molecular and ecophysiological diversity of 28 strains originating from remote sampling sites. None of the investigated populations are homogenous, but are rather heterogeneously composed of different ecotypes and genotypes, possibly corresponding to cryptic species. This population heterogeneity may partly explain the deviations between studies on single strains and populations in both laboratory and field studies. The molecular distance between the strains was correlated with the salinity and temperature adaptation of the respective strains, contradicting the assumption that SSU rRNA variation reflects accumulated neutral mutations. Independent of whether this correlation reflects adaptation above the (biological) species level or variation between asexually reproducing lineages, we demonstrate the unsuitability of the current classification system (species concept) for the investigated organisms, at least with respect to ecological and ecophysiological investigations.
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Evidence for geographic isolation and signs of endemism within a protistan morphospecies.
2006Co-Authors: Jens Boenigk, Karin Pfandl, Tobias Garstecki, Hauke Harms, Gianfranco Novarino, Antonis ChatzinotasAbstract:The possible existence of endemism among microorganisms resulting from and preserved by geographic isolation is one of the most controversial topics in microbial ecology. We isolated 31 strains of “Spumella-like” flagellates from remote sampling sites from all continents, including Antarctica. These and another 23 isolates from a former study were characterized morphologically and by small-subunit rRNA gene sequence analysis and tested for the maximum temperature tolerance. Only a minority of the Spumella morpho- and phylotypes from the geographically isolated Antarctic continent follow the worldwide trend of a linear correlation between ambient (air) temperature during strain isolation and heat tolerance of the isolates. A high percentage of the Antarctic isolates, but none of the isolates from locations on all other continents, were obligate psychrophilic, although some of the latter were isolated at low ambient temperatures. The drastic deviation of Antarctic representatives of Spumella from the global trend of temperature adaptation of this morphospecies provides strong evidence for geographic transport restriction of a microorganism; i.e., Antarctic protistan communities are less influenced by transport of protists to and from the Antarctic continent than by local adaptation, a subtle form of endemism.
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high diversity of the Spumella like flagellates an investigation based on the ssu rrna gene sequences of isolates from habitats located in six different geographic regions
2005Co-Authors: Jens Boenigk, Karin Pfandl, Peter Stadler, Antonis ChatzinotasAbstract:Summary We isolated 28 strains of ‘ Spumella -like’ flagellates from different freshwater and soil habitats in Austria, People’s Republic of China, Nepal, New Zealand, Uganda, Kenya, Tanzania and Hawaii by use of a modified filtration‐acclimatization method. ‘ Spumella -like’ flagellates were found in all of the samples and were often among the dominant bacterivorous flagellates in the respective environments. The small subunit ribosomal RNA (SSU rRNA) gene sequence of the isolates was determined and aligned with previously published sequences of members belonging to the Chrysophyceae sensu stricto . Phylogenetic analysis of the 28 new sequences confirmed their position within the Chrysophyceae sensu stricto and positioned them within different clades. Most of the sequences grouped within clade C and formed several subclusters separated from each other by green taxa including flagellates belonging to Ochromonas , Dinobryon , Poterioochromonas and others. All soil isolates clustered together (subcluster C1) with the soil strain Spumella elongata and the undescribed soil strain ‘Spumella danica’. Aquatic isolates were affiliated with at least two branches (C2 and C3). Sequence similarity to the closest related member of the Chrysophyceae ranged between 92% and 99.6%, sequence divergence among the ‘ Spumella -like’ flagellates was as high as 10%. We conclude that (i) the ‘ Spumella -like’ flagellates are a diverse group both in terms of sequence dissimilarity between isolates and in terms of the number of genotypes, (ii) Spumella and Ochromonas are polyphyletic, and (iii) based on the SSU rRNA gene no biogeographical restriction of certain branches could be observed even though different ecotypes may be represented by the same genotype.
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heavy metal toxicity and bioavailability of dissolved nutrients to a bacterivorous flagellate are linked to suspended particle physical properties
2005Co-Authors: Jens Boenigk, Anneliese Wiedlroither, Karin PfandlAbstract:Many dissolved substances attach easily to sediment particles. In the presence of suspended sediments bioavailability of dissolved substances is therefore, usually reduced and clays are even applied to “wash” natural waters upon pollution. In organisms which feed on food organisms in the size range of these suspended sediment particles, however, bioavailability of such substances may even increase. For microorganisms the interaction with dissolved substances and suspended sediment particles so far has hardly been investigated. We specifically tested: (1) the importance of suspended particles as an uptake route for dissolved substances; and (2) the significance of particle surface properties, i.e. surface load and mineralogy. As a model system we used an axenically cultured strain of a widespread and often abundant flagellate (“ Spumella-like” flagellate strain JBM10). We tested the toxicity of cadmium (II) and mercury (II) as well as availability of dissolved organic matter (DOM) in the absence as well as in the presence of different natural clays, i.e. a kaolinite, a montmorillonite, and a mixed clay, and of artificial silicate particles of different surface charge. When applied separately the presence of the heavy metals cadmium and mercury as well as of suspended particles negatively affected the investigated flagellate but nutritive organics supported growth of the investigated flagellate. Toxic stress response comprises behavioral changes including enhanced swimming activity and stress egestion of ingested particles and was generally similar for a variety of different flagellate species. In combination with suspended particles, the respective effect of trace metals and nutritive substances decreased. Regarding the particle quality, cadmium toxicity increased with increasingly negative surface charge, i.e. increasing surface density of silanol groups (Pearson’s product moment, P = 0.005). For mercury particle mineralogy still had a significant effect ( P < 0.001) but surface load seems to play a minor role and for nutritive organics no significant effect of the investigated particle properties was found. We conclude that: (i) flagellates are as sensitive as higher animals to heavy metal pollution; (ii) suspended particles decrease bioavailability of dissolved substances and ingestion of suspended particles probably play a minor role as uptake route for dissolved substances; and (iii) suspended sediment particle properties, i.e. surface charge and mineralogy, are key factors for the interaction between microorganisms and dissolved substances in the presence of suspended sediments. © 2004 Elsevier B.V. All rights reserved.
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unexpected effects of prey dimensions and morphologies on the size selective feeding by two bacterivorous flagellates ochromonas sp and Spumella sp
2004Co-Authors: Karin Pfandl, Thomas Posch, Jens BoenigkAbstract:Abstract Current models on protistan size-selective feeding assume that contact probability is the factor that largely explains observed food preferences. Contact probability is generally expected to be positively correlated with prey size and therefore to explain observed food selection for larger prey items. We critically tested these basic assumptions on size-selective feeding using the interception-feeding chrysomonad nanoflagellates Ochromonas sp. and Spumella sp. Mechanisms of differential feeding were studied during distinct stages of the selection process (i.e. contact probability, capture efficiency, ingestion efficiency, and differential digestion) by means of high-resolution video microscopy. Food selection was investigated using a mixture of microspheres ranging from 0.3–2.2 μm in diam., as well as a mixed bacterial community. In contrast to current model assumptions, the contact probability was highest for microspheres of intermediate size (0.9–1.2 μm), but was not generally positively correl...
Klaus Jurgens - One of the best experts on this subject based on the ideXlab platform.
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role of bacterial phenotypic traits in selective feeding of the heterotrophic nanoflagellate Spumella sp
2002Co-Authors: Carsten Matz, Jens Boenigk, Hartmut Arndt, Klaus JurgensAbstract:The influence of different bacterial phenotypic traits on the feeding selectivity of a bac- terivorous nanoflagellate was investigated in laboratory experiments. Twelve bacterial isolates from freshwater habitats were characterized in terms of cell size, morphology, capsule formation, surface hydrophobicity and charge, and swimming behavior. Mechanisms of differential flagellate feeding on these isolates were studied in short-term grazing experiments by high-resolution video microscopy using the nanoflagellate Spumella sp. as a model interception-feeding predator. The dif- ferentiation into distinct stages of the feeding process (contact, capture, ingestion) revealed a com- plex selection behavior illustrated by the relatively small proportion of ingested bacteria over cell contacts. We found that bacterial swimming speed increased contact rates but also decreased flagel- late capture efficiency, which had a compensating effect on overall ingestion rates. Bacterial cell size revealed no correlation with flagellate contact rates but an effective inhibition of ingestion rates when exceeding a critical size limit. Correlation analysis presented no bacterial property to account for the residual variability of flagellate ingestion efficiencies. Experiments with specifically coated artificial particles provided evidence for the relative importance of the biochemical surface composi- tion in flagellate food selection compared to physicochemical interaction forces. Only extreme charges beyond -45 mV reduced flagellate ingestion rates. Our results reinforce the idea that bacte- rial cell size strongly affects the feeding success of bacterivorous flagellates, and further implicates size-independent bacterial traits such as swimming speed and biochemical surface composition in this feeding success.
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the influence of preculture conditions and food quality on the ingestion and digestion process of three species of heterotrophic nanoflagellates
2001Co-Authors: Jens Boenigk, Klaus Jurgens, Carsten Matz, Hartmut ArndtAbstract:The influence of prey characteristics such as motility and size as well as of predator characteristics such as satiation and preculturing diet on the feeding process of interception feeding heterotrophic nanoflagellates was investigated. Three species of gram-negative bacteria, one species of gram-positive bacteria, two species of cyanobacteria (Synechococcus) and inert latex particles were fed as prey particles for three species of heterotrophic nanoflagellates (Spumella, Ochromonas, Cafeteria). Ingestion rates depended on the satiation of the flagellates and especially on the filling status of the food vacuoles. In addition, the ingestion rates depended on the characteristics of the food particle and were modified by pre-culturing the flagellates on either Pseudomonas putida or Bacillus subtilis. Digestion was found to be particle-specific. Cyanobacteria were excreted a few minutes after ingestion whereas heterotrophic bacteria were stored and digested in the food vacuoles. The spectrum of ingested particles is not identical to that of digested particles and thus neither the diet of the flagellates nor their impact on bacterial communities can be calculated simply from food vacuole content. "Selective digestion" could be shown to be an important selection mechanism concerning natural food particles. The digestion strategies of Cafeteria on the one hand and Spumella and Ochromonas on the other hand may be an important factor to explain protozoan species composition and succession in the field. In addition to bacterial abundance and grazing pressure by metazooplankton, the bacterial speciescomposition as well as biochemical variations within bacterial species may influence protozoan species composition and abundance.
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digestion of bacterial macromolecules by a mixotrophic flagellate ochromonas sp compared with that by two heterotrophic flagellates Spumella pudica and bodo saltans
2001Co-Authors: Mikhail V Zubkov, Eckart Zollner, Klaus JurgensAbstract:Digestion of bacterial biomass by three species of phagotrophic flagellates was studied using radioactive tracer techniques and short-term feeding experiments. Macromolecules of two different bacterial strains and natural limnic bacterioplankton were pulse-chase-labelled with one of the following precursors 3H-thymidine, 35S-/14C-methionine or 14C-leucine, before bacteria were fed to flagellates and radioactive labels were traced into flagellate macromolecules. The concentrations of prey and predators were monitored by flow cytometry. The aim of the work was to compare efficiencies of bacterial macromolecule accumulation by mixotrophic (Ochromonas) and heterotrophic (Spumella and Bodo) flagellates. We observed that flagellate accumulation efficiency of bacterial macromolecules labelled with thymidine (mean 15–30%, depending on flagellate species) was lower than of bacterial macromolecules labelled with amino acids (mean 26–68%). Heterotrophic flagellate species had similar accumulation efficiencies of bacterial molecules, when either leucine (26–42%) or methionine (31–41%) was used as a tracer. In contrast the mixotrophic flagellate accumulated significantly more residues of labelled methionine (68%) than of labelled leucine (54%). Methionine seems to be accumulated as an intact molecule and possibly Ochromonas preferentially accumulated methionine as an additional source of reduced sulphur. Protozoan accumulation efficiencies did not differ significantly whether the pulse-labelled bacterial prey were from growing or long-term starvation cultures. Our results suggest that labelled amino acids are more appropriate than labelled thymidine for studying transfer of bacterial biomass within food webs.
Antonis Chatzinotas - One of the best experts on this subject based on the ideXlab platform.
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taxonomic and ecological characterization of stomatocysts of Spumella like flagellates chrysophyceae 1
2010Co-Authors: Barbara M Findenig, Antonis Chatzinotas, Jens BoenigkAbstract:Cyst formation is a characteristic feature of chrysophytes. Cyst morphology is used for species identification, and the distribution of cysts in sediment cores is used to infer past climate conditions. The affiliation of stomatocyst demes with morphospecies, however, remains unclear. Here, we investigated the taxonomic and ecological value of the occurrence of cyst formation and cyst morphology to differentiate chrysophyte flagellates of the Spumella-morphodeme, which are among the numerically dominant eukaryotes in many aquatic and terrestrial habitats. In the investigated 90 strains of Spumella-like flagellates, we observed encystment only in six strains despite the broad range of temperature regimes and chemical factors tested. Spumella-like flagellates that produce cysts are affiliated with different subclusters within the Chrysophyceae and are closely related to strains for which cyst formation is not known. The occurrence of cyst formation is therefore unsuitable as a taxonomic criterion. Cyst morphology allows for differentiating some strains even though distinctly different strains may have similar or even identical-looking cyst demes. Despite considerable changes in cell size of the vegetative cells related to the nutritional status, the size of the cysts was always larger than that of a typical vegetative cell. Cysts were colorless and had no chromatophores, and some granula were visible in the light microscope. None of the investigated strains and none of the so far published cyst descriptions of Spumella spp. entirely seem to match the cyst description of the generic type strain. However, taking methodological bias between light and electron microscopical investigations into account, the cysts 199hm (this paper) and N1846 (Yubuki et al. 2008) seem to correspond to the cyst of the generic type strain. We propose the strain 199hm as epitype for Spumella vulgaris Cienkowsky; we further describe Spumella rivalis Boenigk et Findenig sp. nov., PedoSpumella encystans Boenigk et Findenig gen. et sp. nov., and PoterioSpumella lacustris Boenigk et Findenig gen. et sp. nov.
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SSU rRNA gene variation resolves population heterogeneity and ecophysiological differentiation within a morphospecies (Stramenopiles, Chrysophyceae)
2009Co-Authors: Karin Pfandl, Antonis Chatzinotas, Patricia Dyal, Jens BoenigkAbstract:The objective of this study was to analyze the extent of ecophysiological and molecular homogeneity, or heterogeneity, of distinct protist populations and to test for correlations between molecular distance and ecophysiological adaptation in a widespread and ubiquitous protistan taxon. We selected heterotrophic nanoflagellates of the Spumella morphotype as a model organism, because these flagellates are widespread and among the dominant bacterivores in many microbial communities. We investigated the molecular microdiversity and the ecophysiological tolerances for a total of 13 strains originating from two freshwater samples. We further investigated the affiliation of different ecotypes with distinct small subunit ribosomal ribonucleic acid (SSU rRNA) genotypes, or molecular operational taxonomic units. These regional population studies were further compared to the molecular and ecophysiological diversity of 28 strains originating from remote sampling sites. None of the investigated populations are homogenous, but are rather heterogeneously composed of different ecotypes and genotypes, possibly corresponding to cryptic species. This population heterogeneity may partly explain the deviations between studies on single strains and populations in both laboratory and field studies. The molecular distance between the strains was correlated with the salinity and temperature adaptation of the respective strains, contradicting the assumption that SSU rRNA variation reflects accumulated neutral mutations. Independent of whether this correlation reflects adaptation above the (biological) species level or variation between asexually reproducing lineages, we demonstrate the unsuitability of the current classification system (species concept) for the investigated organisms, at least with respect to ecological and ecophysiological investigations.
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Evidence for geographic isolation and signs of endemism within a protistan morphospecies.
2006Co-Authors: Jens Boenigk, Karin Pfandl, Tobias Garstecki, Hauke Harms, Gianfranco Novarino, Antonis ChatzinotasAbstract:The possible existence of endemism among microorganisms resulting from and preserved by geographic isolation is one of the most controversial topics in microbial ecology. We isolated 31 strains of “Spumella-like” flagellates from remote sampling sites from all continents, including Antarctica. These and another 23 isolates from a former study were characterized morphologically and by small-subunit rRNA gene sequence analysis and tested for the maximum temperature tolerance. Only a minority of the Spumella morpho- and phylotypes from the geographically isolated Antarctic continent follow the worldwide trend of a linear correlation between ambient (air) temperature during strain isolation and heat tolerance of the isolates. A high percentage of the Antarctic isolates, but none of the isolates from locations on all other continents, were obligate psychrophilic, although some of the latter were isolated at low ambient temperatures. The drastic deviation of Antarctic representatives of Spumella from the global trend of temperature adaptation of this morphospecies provides strong evidence for geographic transport restriction of a microorganism; i.e., Antarctic protistan communities are less influenced by transport of protists to and from the Antarctic continent than by local adaptation, a subtle form of endemism.
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high diversity of the Spumella like flagellates an investigation based on the ssu rrna gene sequences of isolates from habitats located in six different geographic regions
2005Co-Authors: Jens Boenigk, Karin Pfandl, Peter Stadler, Antonis ChatzinotasAbstract:Summary We isolated 28 strains of ‘ Spumella -like’ flagellates from different freshwater and soil habitats in Austria, People’s Republic of China, Nepal, New Zealand, Uganda, Kenya, Tanzania and Hawaii by use of a modified filtration‐acclimatization method. ‘ Spumella -like’ flagellates were found in all of the samples and were often among the dominant bacterivorous flagellates in the respective environments. The small subunit ribosomal RNA (SSU rRNA) gene sequence of the isolates was determined and aligned with previously published sequences of members belonging to the Chrysophyceae sensu stricto . Phylogenetic analysis of the 28 new sequences confirmed their position within the Chrysophyceae sensu stricto and positioned them within different clades. Most of the sequences grouped within clade C and formed several subclusters separated from each other by green taxa including flagellates belonging to Ochromonas , Dinobryon , Poterioochromonas and others. All soil isolates clustered together (subcluster C1) with the soil strain Spumella elongata and the undescribed soil strain ‘Spumella danica’. Aquatic isolates were affiliated with at least two branches (C2 and C3). Sequence similarity to the closest related member of the Chrysophyceae ranged between 92% and 99.6%, sequence divergence among the ‘ Spumella -like’ flagellates was as high as 10%. We conclude that (i) the ‘ Spumella -like’ flagellates are a diverse group both in terms of sequence dissimilarity between isolates and in terms of the number of genotypes, (ii) Spumella and Ochromonas are polyphyletic, and (iii) based on the SSU rRNA gene no biogeographical restriction of certain branches could be observed even though different ecotypes may be represented by the same genotype.
Hartmut Arndt - One of the best experts on this subject based on the ideXlab platform.
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role of bacterial phenotypic traits in selective feeding of the heterotrophic nanoflagellate Spumella sp
2002Co-Authors: Carsten Matz, Jens Boenigk, Hartmut Arndt, Klaus JurgensAbstract:The influence of different bacterial phenotypic traits on the feeding selectivity of a bac- terivorous nanoflagellate was investigated in laboratory experiments. Twelve bacterial isolates from freshwater habitats were characterized in terms of cell size, morphology, capsule formation, surface hydrophobicity and charge, and swimming behavior. Mechanisms of differential flagellate feeding on these isolates were studied in short-term grazing experiments by high-resolution video microscopy using the nanoflagellate Spumella sp. as a model interception-feeding predator. The dif- ferentiation into distinct stages of the feeding process (contact, capture, ingestion) revealed a com- plex selection behavior illustrated by the relatively small proportion of ingested bacteria over cell contacts. We found that bacterial swimming speed increased contact rates but also decreased flagel- late capture efficiency, which had a compensating effect on overall ingestion rates. Bacterial cell size revealed no correlation with flagellate contact rates but an effective inhibition of ingestion rates when exceeding a critical size limit. Correlation analysis presented no bacterial property to account for the residual variability of flagellate ingestion efficiencies. Experiments with specifically coated artificial particles provided evidence for the relative importance of the biochemical surface composi- tion in flagellate food selection compared to physicochemical interaction forces. Only extreme charges beyond -45 mV reduced flagellate ingestion rates. Our results reinforce the idea that bacte- rial cell size strongly affects the feeding success of bacterivorous flagellates, and further implicates size-independent bacterial traits such as swimming speed and biochemical surface composition in this feeding success.
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the influence of preculture conditions and food quality on the ingestion and digestion process of three species of heterotrophic nanoflagellates
2001Co-Authors: Jens Boenigk, Klaus Jurgens, Carsten Matz, Hartmut ArndtAbstract:The influence of prey characteristics such as motility and size as well as of predator characteristics such as satiation and preculturing diet on the feeding process of interception feeding heterotrophic nanoflagellates was investigated. Three species of gram-negative bacteria, one species of gram-positive bacteria, two species of cyanobacteria (Synechococcus) and inert latex particles were fed as prey particles for three species of heterotrophic nanoflagellates (Spumella, Ochromonas, Cafeteria). Ingestion rates depended on the satiation of the flagellates and especially on the filling status of the food vacuoles. In addition, the ingestion rates depended on the characteristics of the food particle and were modified by pre-culturing the flagellates on either Pseudomonas putida or Bacillus subtilis. Digestion was found to be particle-specific. Cyanobacteria were excreted a few minutes after ingestion whereas heterotrophic bacteria were stored and digested in the food vacuoles. The spectrum of ingested particles is not identical to that of digested particles and thus neither the diet of the flagellates nor their impact on bacterial communities can be calculated simply from food vacuole content. "Selective digestion" could be shown to be an important selection mechanism concerning natural food particles. The digestion strategies of Cafeteria on the one hand and Spumella and Ochromonas on the other hand may be an important factor to explain protozoan species composition and succession in the field. In addition to bacterial abundance and grazing pressure by metazooplankton, the bacterial speciescomposition as well as biochemical variations within bacterial species may influence protozoan species composition and abundance.
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the problematic nature of fluorescently labeled bacteria flb in Spumella feeding experiments an explanation by using video microscopy
2001Co-Authors: Jens Boenigk, Hartmut Arndt, Ernstjosef ClevenAbstract:Video microscopy was applied to observe the feeding by Spumella on fluorescently labeled bacteria (FLB) as well as on unstained bacteria. Ingestion rates were similar for unstained bacteria and for FLB. However, FLB were egested after a vacuole passage time of about three minutes while the vacuole passage time of unstained bacteria exceeded twenty minutes. Significant differences were found between the cumulative number of subsequent observed ingestions of FLB and food vacuole content. The assumption of a similar treatment of FLB and unstained living bacteria is therefore incorrect for Spumella. Thus, ingestion rates calculated from the number of FLB in food vacuoles underestimate real ingestion of this species.