The Experts below are selected from a list of 462 Experts worldwide ranked by ideXlab platform
Isabelle Domaizon - One of the best experts on this subject based on the ideXlab platform.
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Community structure and dynamics of small eukaryotes targeted by new oligonucleotide probes: New insight into the lacustrine microbial food web
Applied and Environmental Microbiology, 2009Co-Authors: Jean-françois Mangot, Cécile Lepère, Didier Debroas, Christophe Bouvier, Isabelle DomaizonAbstract:The seasonal dynamics of the small eukaryotic fraction (cell diameter, 0.2 to 5 microm) was investigated in a mesotrophic lake by tyramide signal amplification-fluorescence in situ hybridization targeting seven different phylogenetic groups: Chlorophyceae, Chrysophyceae, Cryptophyceae, Cercozoa, LKM11, Perkinsozoa (two clades), and Fungi. The abundance of small eukaryotes ranged from 1,692 to 10,782 cells ml(-1). The dominant groups were the Chrysophyceae and the Chlorophyceae, which represented 19.6% and 17.9% of small eukaryotes, respectively. The results also confirmed the quantitative importance of putative parasites, Fungi and Perkinsozoa, in the small heterotrophic eukaryotic assemblage. The relative abundances recorded for the Perkinsozoa group reached as much as 31.6% of total targeted eukaryotes during the summer. The dynamics of Perkinsozoa clade 1 coincided with abundance variations in Peridinium and Ceratium spp. (Dinoflagellates), while the dynamics of Perkinsozoa clade 2 was linked to the presence of Dinobryon spp. (Chrysophyceae). Fungi, represented by chytrids, reached maximal abundance in December (569 cells ml(-1)) and were mainly correlated with the dynamics of diatoms, especially Melosira varians. A further new finding of this study is the recurrent presence of Cercozoa (6.2%) and LKM11 (4.5%) cells. This quantitative approach based on newly designed probes offers a promising means of in-depth analysis of microbial food webs in lakes, especially by revealing the phylogenetic composition of the small heterotrophic flagellate assemblage, for which an important fraction of cells are generally unidentified by classical microscopy (on average, 96.8% of the small heterotrophic flagellates were identified by the specific probes we used in this study).
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taxon specific and seasonal variations in flagellates grazing on heterotrophic bacteria in the oligotrophic lake annecy importance of mixotrophy
FEMS Microbiology Ecology, 2003Co-Authors: Isabelle Domaizon, Sylvie Viboud, Dominique FontvieilleAbstract:We investigated the taxonomic composition of flagellate assemblages and taxon-specific bacterial grazing rates of heterotrophic and mixotrophic flagellates in the oligotrophic Lake Annecy (France). The comparison of bacterial grazing rates to bacterial production demonstrated a high transfer efficiency from the bacterial compartment up to flagellates. Per capita grazing rates ranged from 1.2×103 to 5.1×106 bacteria l−1 h−1 for heterotrophic flagellates, and from 4.8×106 to 6.8×107 bacteria l−1 h−1 for mixotrophic flagellates. The main bacterial grazers were Katablepharis within heterotrophic flagellates and Dinobryon within mixotrophic flagellates. Our results show that bacterial ingestion by a given flagellate taxon changed seasonally and could vary up to 30-fold. We also provide evidence that mixotrophic flagellates represent an important link in the flux of materials through planktonic food webs in Lake Annecy, suggesting that the introduction of mixotrophs within functional groups could improve our understanding of carbon flux pathways.
Jordi Catalan - One of the best experts on this subject based on the ideXlab platform.
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some mixotrophic flagellate species selectively graze on archaea
Applied and Environmental Microbiology, 2017Co-Authors: Miguel Ballensegura, Marisol Felip, Jordi CatalanAbstract:Many phototrophic flagellates ingest prokaryotes. This mixotrophic trait becomes a critical aspect of the microbial loop in planktonic food webs because of the typical high abundance of these flagellates. Our knowledge of their selective feeding upon different groups of prokaryotes, particularly under field conditions, is still quite limited. In this study, we investigated the feeding behavior of three species (Rhodomonas sp., Cryptomonas ovata, and Dinobryon cylindricum) via their food vacuole content in field populations of a high mountain lake. We used the catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) protocol with probes specific for the domain Archaea and three groups of Eubacteria: Betaproteobacteria, Actinobacteria, and Cytophaga-Flavobacteria of Bacteroidetes Our results provide field evidence that contrasting selective feeding exists between coexisting mixotrophic flagellates under the same environmental conditions and that some prokaryotic groups may be preferentially impacted by phagotrophic pressure in aquatic microbial food webs. In our study, Archaea were the preferred prey, chiefly in the case of Rhodomonas sp., which rarely fed on any other prokaryotic group. In general, prey selection did not relate to prey size among the grazed groups. However, Actinobacteria, which were clearly avoided, mostly showed a size of <0.5 μm, markedly smaller than cells from the other groups. IMPORTANCE That mixotrophic flagellates are not randomly feeding in the main prokaryotic groups under field conditions is a pioneer finding in species-specific behavior that paves the way for future studies according to this new paradigm. The particular case that Archaea were preferentially affected in the situation studied shows that phagotrophic pressure cannot be disregarded when considering the distribution of this group in freshwater oligotrophic systems.
Miguel Ballensegura - One of the best experts on this subject based on the ideXlab platform.
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some mixotrophic flagellate species selectively graze on archaea
Applied and Environmental Microbiology, 2017Co-Authors: Miguel Ballensegura, Marisol Felip, Jordi CatalanAbstract:Many phototrophic flagellates ingest prokaryotes. This mixotrophic trait becomes a critical aspect of the microbial loop in planktonic food webs because of the typical high abundance of these flagellates. Our knowledge of their selective feeding upon different groups of prokaryotes, particularly under field conditions, is still quite limited. In this study, we investigated the feeding behavior of three species (Rhodomonas sp., Cryptomonas ovata, and Dinobryon cylindricum) via their food vacuole content in field populations of a high mountain lake. We used the catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) protocol with probes specific for the domain Archaea and three groups of Eubacteria: Betaproteobacteria, Actinobacteria, and Cytophaga-Flavobacteria of Bacteroidetes Our results provide field evidence that contrasting selective feeding exists between coexisting mixotrophic flagellates under the same environmental conditions and that some prokaryotic groups may be preferentially impacted by phagotrophic pressure in aquatic microbial food webs. In our study, Archaea were the preferred prey, chiefly in the case of Rhodomonas sp., which rarely fed on any other prokaryotic group. In general, prey selection did not relate to prey size among the grazed groups. However, Actinobacteria, which were clearly avoided, mostly showed a size of <0.5 μm, markedly smaller than cells from the other groups. IMPORTANCE That mixotrophic flagellates are not randomly feeding in the main prokaryotic groups under field conditions is a pioneer finding in species-specific behavior that paves the way for future studies according to this new paradigm. The particular case that Archaea were preferentially affected in the situation studied shows that phagotrophic pressure cannot be disregarded when considering the distribution of this group in freshwater oligotrophic systems.
Zulkifly Shahrizim - One of the best experts on this subject based on the ideXlab platform.
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Current status of algae biodiversity and succession in North Lake of Hutan Simpan Ayer Hitam, Puchong
Department of Biology Faculty of Science Universiti Putra Malaysia, 2016Co-Authors: Abdullah S., Ismail N. S., Zulkifly ShahrizimAbstract:This study presents data on the diversity and succession of algae in North Lake, Hutan Simpan Air Hitam (HSAH) as well as its relationship with chemical and physical factors. Algae samples were collected weekly from three different sites in North Lake started from October 2015 until January 2016 (15 weeks). Physico-chemical parameters such as pH, temperature, light, dissolved oxygen (DO), total dissolved solid (TDS) and nutrients statuses were measured simultaneously. A total of 18 species were recorded comprising Bacillariophyta (3 species), Charophyta (4 species), Chlorophyta (4 species), Cyanobacteria (2 species), Dinophyta (4 species), and Ochrophyta (1 species). The highest total density of algal cells were phyla Dinophyta (24%) followed by Charophyta (22%), Bacillariophyta (19%), Ochrophyta (18%), Cyanophyta (10%) and Chlorophyta (7%). Dinobryon sertularia was the most frequent species found throughout the 15 weeks of sampling and became dominant in week 3, 4, 6, 10 and 13; whereas Staurastrum sp. achieved the highest algal counts in week 1 and 2. Gonyaulax apiculata was dominant during week 5, 8, 14 and 15. The Shannon-Weaver diversity Index, H’ classified North Lake as being moderately polluted, whereas the pH values indicates that the lake was quite acidic by having pH lower than 7 and ranged between 4.28 and 5.57. The occurrence of some phytoplankton groups may be influenced by pH, as has been found in acidic natural lakes and also in extremely acidic lakes around the world. In addition, other physico-chemical factors may also give impact on algae structure and community
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Algal communities analysis as an assessment of the trophic status of Ayer Hitam Forest Reserve
2015Co-Authors: Ghazali, Fatheen Nadira, Duraivelu Thirubuvanesvari, Sukardi, Nur Syafiza, Zulkifly ShahrizimAbstract:Studies of algal biodiversity in relation to nutrient status of water bodies in Malaysia are lacking. In Ayer Hitam Forest Reserve (AHFR), succession of the freshwater algae and physico-chemical parameters were studied in 16 weeks starting from November 2014 until February 2015. Identification and enumeration of algae cells were done using Neubauer chamber (hemocytometer), whereas physico-chemical parameters including pH, water temperature, light intenstiy, dissolved oxygen, total dissolved solid were determined in situ. Parameters such as ammonia, nitrate, phosphate and silica were measured in the laboratory. Pearson Correlation Analysis principal component analysis (PCA) and canonical component analysis (CCA) were used to establish correlation with the physico-chemical parameters such as light intensity, temperature, pH, total dissolved solid, dissolved oxygen and nutrients status including the concentration of ammonia, nitrate, phosphate and silica. Dominating algae species found were Dinobryon sertularia, Gymnodinium palustre, Gonyaulax apiculata and Navicula sp. . Gonyaulax apiculata and Dinobryon sertularia were found to have correlation with total dissolved solid, nitrate, phosphate and light intensity. Shannon-weaver and evenness indices were used to measure the species diversity at the lake and indicated that the lake was low in nutrients (oligotrophic lake). The species richness and diversity was quite stable and the water in the lake was indicated as moderately polluted. Due to the acidic condition of the lake, only selected algae species tolerated, survived and dominated the lake
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Biodiversity and succession of freshwater algae in Hutan Simpan Ayer Hitam Forest Reserve, Puchong Selangor
Department of Biology Faculty of Science Universiti Putra Malaysia, 2014Co-Authors: Zulkifly Shahrizim, Uyob, Intan Farhanna, Sahar NoraishahAbstract:The succession and dominant of freshwater algae were studied in the north lake of Ayer Hitam Forest Reserve. Sampling was performed for thirteen weeks, from the end of the November 2013 to the end of the February 2014. Water sampling for biological analysis was done during the thirteen weeks. The structural community was determined by population density, class of algae and diversity indices. The community of freshwater algae consisted of 15 species from 5 different phyla which are Ochrophyta, Dinophyta, Charophyta, Cyanophyta and Chlorophyta. The Dinophyta had the highest total density in the thirteen weeks and two species from three species of Dinophyta were the most conspicuous species in the succession which are Gonyaulax apiculata and Gymnodinium palustre. The dominance of Dinophyta was during week 2, 3, 6, 7, 10 and 11. Dinobryon sertularia from phylum Ochrophyta had the highest density and being dominant during week 1, 4 and 5. For the Cyanophyta, Anabaena subcylindrica had the highest density as compared to the other species of Cyanophyta. Anabaena subcylindrica was being dominant during week 8, 9 and 13. For diatom Navicula sp. (Ochrophyta), the highest density was obtained during week 12. The Shannon-Weaver index had the highest during week 12 and the lowest during week 4. The highest Evenness index occurred during week 3 and the lowest during week 4. The pattern of succession and dominant of freshwater algae in a north lake of AHFR was associated with the physico-chemical parameter especially nutrient status, pH, temperature and light intensity
Jean-françois Mangot - One of the best experts on this subject based on the ideXlab platform.
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Community structure and dynamics of small eukaryotes targeted by new oligonucleotide probes: New insight into the lacustrine microbial food web
Applied and Environmental Microbiology, 2009Co-Authors: Jean-françois Mangot, Cécile Lepère, Didier Debroas, Christophe Bouvier, Isabelle DomaizonAbstract:The seasonal dynamics of the small eukaryotic fraction (cell diameter, 0.2 to 5 microm) was investigated in a mesotrophic lake by tyramide signal amplification-fluorescence in situ hybridization targeting seven different phylogenetic groups: Chlorophyceae, Chrysophyceae, Cryptophyceae, Cercozoa, LKM11, Perkinsozoa (two clades), and Fungi. The abundance of small eukaryotes ranged from 1,692 to 10,782 cells ml(-1). The dominant groups were the Chrysophyceae and the Chlorophyceae, which represented 19.6% and 17.9% of small eukaryotes, respectively. The results also confirmed the quantitative importance of putative parasites, Fungi and Perkinsozoa, in the small heterotrophic eukaryotic assemblage. The relative abundances recorded for the Perkinsozoa group reached as much as 31.6% of total targeted eukaryotes during the summer. The dynamics of Perkinsozoa clade 1 coincided with abundance variations in Peridinium and Ceratium spp. (Dinoflagellates), while the dynamics of Perkinsozoa clade 2 was linked to the presence of Dinobryon spp. (Chrysophyceae). Fungi, represented by chytrids, reached maximal abundance in December (569 cells ml(-1)) and were mainly correlated with the dynamics of diatoms, especially Melosira varians. A further new finding of this study is the recurrent presence of Cercozoa (6.2%) and LKM11 (4.5%) cells. This quantitative approach based on newly designed probes offers a promising means of in-depth analysis of microbial food webs in lakes, especially by revealing the phylogenetic composition of the small heterotrophic flagellate assemblage, for which an important fraction of cells are generally unidentified by classical microscopy (on average, 96.8% of the small heterotrophic flagellates were identified by the specific probes we used in this study).