Télesphore Sime-Ngando

Publications (130) View all

• Article: [Revision of of the subfamily of Metaracoelophryinae de Puytorac 1972 (Oligohymenophora: Hoplytophryida: Hoplytophryidae), astome ciliates of the digestive tract of Oligochaeta worms of Africa: description of five new species].

  Z Fokam, P Ngassam, P A Nana, G Bricheux, P Bouchard, T Sime Ngando
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  ABSTRACT: Five new species belonging to the astome ciliates, living in the digestive tract of Oligochaeta worms belonging to the genus Alma from Cameroon, have been described. The techniques used are: vital staining, staining of the nucleus with Diamidino Phenyl Indol (DAPI), scanning electron microscopy and silver staining method (Fernandez Galiano, 1976, 1994). This work confirms the presence of the genus Paracoelophrya and Dicoelophrya in the digestive track of the oligochaete Alma from Gabon and Cameroon; it helps to understand the general taxonomy of this Metaracoelophryinae subfamily. Moreover, the homogeneity of this group is confirmed and the phylogenetic relationship inside the Hoplitophryida order need more studies to be solved.
  Parasite (Paris, France) 02/2012; 19(1):41-52. · 1.00 Impact Factor
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  Available from: Télesphore Sime-Ngando

  Article: High lytic infection rates but low abundances of prokaryote viruses in a humic lake (Vassivière, Massif Central, France).

  A S Pradeep Ram, S Rasconi, M Jobard, S Palesse, J Colombet, T Sime-Ngando
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  ABSTRACT: We explored the abundance and infection rates of viruses on a time series scale in the euphotic zone of the humic mesotrophic Lake Vassivière (Massif Central, France) and compared them to nonhumic lakes of contrasting trophy (i.e., the oligomesotrophic Lake Pavin and the eutrophic Lake Aydat) located in the same geographical region and sampled during the same period. In Lake Vassivière, the abundances of virus-like particles (range, 1.7 × 10(10) to 2.6 × 10(10) liter(-1)) were significantly (P < 0.001) lower than in Lakes Pavin and Aydat. The percentage of virus-infected prokaryotic cells (mean, 18.0%) was significantly higher (P < 0.001) in Vassivière than in Pavin (mean, 11.5%) and Aydat (mean, 9.7%). In Vassivière, the abundance of prokaryotes was a good predictor (r = 0.78, P < 0.001) of the number of virus-like particles, while the potential grazing rate from heterotrophic nanoflagellates was positively correlated to the viral infection rate (r = 0.75, P < 0.001; n = 20), indicating the prevalence of cycling interactions among viruses, prokaryotes, and grazers, which is in agreement with past experiments. The absence of correlation between chlorophyll a concentrations (Chl) and viral parameters suggested that the resources for the lytic activity of viruses in Vassivière were mainly under allochthonous control, through host activity. Indeed, compilation of data obtained from several nonhumic lakes in the French Massif Central revealed that Chl was positively correlated to the abundance of virus-like particles at concentrations above 0.5 μg Chl liter(-1) and negatively at concentrations below 0.5 μg Chl liter(-1), suggesting that phytoplankton-derived resources could force prokaryotic growth to attain a certain threshold level when the host availability is sufficient to boost the proliferation of viruses. Therefore, based on the high level of lytic infection rates in Lake Vassivière, we conclude that viruses are key agents for prokaryotic mortality and could influence the food web dynamics in humic lakes, which may ultimately depend on the internal cycling of resources and, perhaps, mainly on the allochthonous inputs and the associated humic substances.
  Applied and environmental microbiology 07/2011; 77(16):5610-8. · 3.69 Impact Factor
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  Available from: John R Dolan

  Article: Microbial food webs and metabolic state across oligotrophic waters of the Mediterranean Sea during summer

  U Christaki, F Van Wambeke, D Lefevre, A Lagaria, L Prieur, M Pujo-Pay, J.-D Grattepanche, J Colombet, S Psarra, J R Dolan, T Sime-Ngando, P Conan, M G Weinbauer, T Moutin
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  ABSTRACT: The abundance and activity of the major members of the heterotrophic microbial community – from viruses to ciliates – were studied along a longitudinal transect across the Mediterranean Sea in the summer of 2008. The Mediter-ranean Sea is characterized by a west to east gradient of deep-ening of DCM (deep chlorophyll maximum) and increasing oligotrophy reflected in gradients of biomass and production. However, within this well documented longitudinal trend, hydrological mesoscale features exist and likely influence microbial dynamics. Here we present data from a W-E tran-sect of 17 stations during the period of summer stratification. Along the transect the production and fate of organic matter was investigated at three selected sites each one located in the centre of an anticyclonic eddy: in the Algero-Provencal Basin (St. A), the Ionian Basin (St. B), and the Levantine Basin (St. C). The 3 geographically distant eddies showed low values of the different heterotrophic compartments of the microbial food web, and except for viruses in site C, all inte-grated (0–150 m) stocks were higher in reference stations lo-Correspondence to: U. Christaki (urania.christaki@univ-littoral.fr) cated in the same basin outside the eddies. During our study the 3 eddies showed equilibrium between GPP (Gross Pri-mary Production) and DCR (Dark Community Respiration). Integrated PPp (Particulate Primary Production) values at A, B and C varied from ∼140 to ∼190 mg C m −2 .
  Biogeosciences 01/2011; 8:1839-1852. · 3.86 Impact Factor
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  Available from: Marie-Elodie Perga

  Article: Food quality of anemophilous plant pollen for zooplankton

  Hélène Masclaux, Alexandre Bec, Maiko Kagami, Marie-Elodie Perga, Telesphore Sime-Ngando, Christian Desvilettes, Gilles Bourdier
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  ABSTRACT: Pollen rain can lead to considerable allochthonous particulate organic carbon input into freshwater systems. However, the importance of allochthonous pollen deposition for zooplankton production has not so far been considered. Here, standardized growth experiments were performed to assess the quality of pollen from three species (Alnus sp., Populus sp., and Cedrus sp.) as a food source for two cladocerans (Daphnia longispina and Simocephalus vetulus). Although lipid analysis revealed high polyunsaturated fatty acid (PUFA) contents in pollen, both cladoceran species exhibited suboptimal development when directly fed on pollen (ranging from 0.2 d 21 to 0.3 d 21). The low food value of pollen was attributed to the presence of a refractory wall reducing its digestibility. In a second set of experiments, cladocerans were fed on a mixture of heterotrophic microorganisms (bacteria, chytrids, and protozoa) that had grown on pollen grains (Cedrus sp.). The introduction of microorganisms as an intermediate trophic level resulted in cladoceran growth rates that were about double those obtained on pollen alone. Hence, our findings suggest that pollen carbon could sustain zooplankton growth indirectly, and highlight the key role of microorganisms, and especially of chytrids, in transferring and upgrading pollen PUFA to higher trophic levels.
  Limnology and oceanography 01/2011; 56:939-946. · 3.42 Impact Factor
• Article: A double staining method using SYTOX-green and Calcofluor White for studying fungal parasites of phytoplankton.

  Mélanie Gerphagnon, Delphine Latour, Jonathan Colombet, Télesphore Sime-Ngando
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  ABSTRACT: We propose a double staining method based on the combination of two fluorochromes, Calcofluor White (CFW, specific chitinous fluorochrome) and SYTOX-green (nucleic acid stain), coupled to epifluorescence microscopy for counting, identifying, and investigating the fecundity of parasitic fungi of phytoplankton and the putative relationships established between the host and their chytrid parasites. The method was applied to freshwater samples collected over two successive years during the terminal period of autumnal cyanobacterial blooms in a eutrophic lake. The study focused on the uncultured host-parasite couple Anabaena macrospora (cyanobacterium) and Rhizosiphon akinetum (Chytridiomycota). Our results showed that up to 36.6% of cyanobacterial akinetes could be parasitized by fungi. Simultaneously, we directly investigated the zoosporic content inside the sporangia, and found that both the host size and intensity of infection conditioned the final size and hence fecundity of the chytrids. We found that relationships linking host size, final parasite size and chytrid fecundity were conserved from year to year, and seemed to be host-chytrid couple specific. We concluded that our double staining method was a valid procedure for improving our knowledge of uncultured freshwater phytoplankton-chytrid couples, and so of the quantitative ecology of chytrids in freshwater ecosystems.
  Applied and environmental microbiology 04/2013; · 3.69 Impact Factor