250 research outputs found
Seasonal Depth-Related Gradients in Virioplankton: Lytic Activity and Comparison with Protistan Grazing Potential in Lake Pavin (France)
International audienceThis study presents an original depth-related survey of virioplankton lytic activity in relation to prokaryotic production and potential protistan bacterivory in the deep (Zmax092 m) meromictic volcanic Lake Pavin (Massif Central, France). The sampling strategy was designed to be representative of the physico-chemical gradients of the water column of the lake, and of the seasonal variability as well, i.e. 12 different depths sampled in triplicates from April to December 2005. In the space, viral lytic activity estimated from the frequency of visibly infected prokaryotic cells and from burst size over the study period generally decreased with depth. This was viewed as a paradox compared to the abundances of viruses and prokaryotes and to the prokaryotic production which increased with depth. The seasonal variability in viral lytic activity was correlated with prokaryotic variables (abundance and production) in the deepest waters, i.e. from the hypolimnion downwards. Compared to previous studies known from the mixolimnion, we conclude that the deep waters in Lake Pavin represent an exclusive environment for heterotrophic prokaryotes whose seasonal activity offers an optimal and unique resource for thriving viral communities, some of which may be typical, endemic to the ambient dark, cold and stable deep water masses. Overall, the main findings in the present study get well around a previous statement that the ecology of the deepest waters of Lake Pavin is essentially driven by the dark viral loop (dissolved organic matter-prokaryotes- viruses) processes, which can sequester organic matters and nutrients for a long-lived turnover time. This is in agreement with recent demonstrations from marine systems that meso- and bathypelagic waters are optimal environments for viral survival and proliferation
Editorial: Roles and mechanisms of parasitism in aquatic microbial communities
International audienc
Dysbiosis in inflammatory bowel disease: a role for bacteriophages?
International audienceIntestinal bacteria have been implicated in theinitiation and amplification of inflammatory bowel disease (IBD). The dysbiosis theory, reviewed by Tamboli et al (Gut 2004;53:1), is that an imbalance between putative ââharmful'' versus ââprotective'' bacterial species may promote chronic intestinal inflammation
Virus, bactéries et protistes pathogÚnes du phytoplancton, le rÎle insoupçonné des parasites dans le fonctionnement des écosystÚmes aquatiques
International audienceMicroscopiques, les parasites sont la plupart du temps invisibles, mais présents partout. Ils infectent tous les organismes du monde vivant. La derniÚre décennie a révélé une incroyable diversité chez les parasites viraux, bactériens et eucaryotes. Ceux infectant le phytoplancton pourraient avoir une importance capitale dans la dynamique des populations algales et dans le fonctionnement des écosystÚmes aquatiques, mais leur rÎle est encore trÚs largement méconnu à ce jour (Brussaard, 2004). Sur ces questions, la recherche ne fait que commencer
Description of five new species of hysterocinetian ciliates (Ciliophora, Hysterocinetidae), endocommensal in a terrestrial oligochaete of the genus Alma from Cameroon
International audienceStudies on five new species of hysterocinetian ciliates, endocommensal within a terrestrial oligochaete from the genus Alma (Cameroon), reveal the existence of three distinct types of cytoskeletal topography within their adhesive apparatus. In the first topographical type, four superimposed antagonistic strata of skeletal fibres that correspond to the arrangement observed in the genus Ptychostomum, Stein 1860 are found. The second topographical type is characterized by the existence of an unorganized field of fibrillar structures forming a single dense mass in the central part of the sucker. For this, a new genus is created: Ptychostomoides, Nana, Fokam, Ntoungwa et al. n. g. The third type present in the genus Proptychostomoides, Nana, Fokam, Ntoungwa et al. n. g. differs from the latter by the existence of a bare patch within the central region of the adhesive apparatus. This new evidence of morphological diversification within the Hysterocinetidae supports a new approach to the systematics of this group
Distribution of Astomatia Schewiakoff, 1896 and Hysterocinetidae Diesing, 1866 (Ciliophora, Oligohymenophora) along the digestive tract of Alma emini (Oligochaete, Glossoscolecidae) is correlated with physico-chemical parameters
International audienceThe paper demonstrates the influence of physico-chemical parameters on the distribution of endocommensal ciliates through the gut of the earthworm Alma emini. We measured physico-chemical parameters of the intestinal liquid extracted with the vacuum aspiration technique and concomitantly recorded biological parameter (species abundance). Furthermore, correlation analysis between physico-chemical parameters and biological parameter was performed in different compartments. In the foregut, among the eleven species of Astomatia recorded, correlation was significant between Metaracoelophrya intermedia, Coelophrya roquei and Water Content (WC = 46.94 ± 7.77%). In the midgut, among the nine species of Hysterocinetidae recorded, a significant correlation was observed between Metaptychostomum ebebdae, Ptychostomum macrostomum and Electric Conductivity (EC = 84.55 ± 12.94 ΌS/ cm). In the same compartment, a significant correlation was also observed between Ptychostomum macrostomum and Total Dissolved Substance (TDS = 16.20 ± 3.46%). In the hindgut, eight species of Astomatia were found, among which significant correlation was obtained between Coelophrya roquei and Hydrogen potential (pH = 7.35 ± 0.16). In the same compartment, taking into account the eleven species of Hysterocinetidae recorded, a significant correlation was also obtained between Ptychostomum macrostomum and pH; Ptychostomum commune and WC (28.84 ± 3.97%). These results suggest that each part of the digestive tract of A. emini can be considered as a set of natural microhabitats in which certain physico-chemical factors generate ecological niches suitable for one or another group of species
Hygroregulation, a key ability for eusocial insects: Native Western European honeybees as a case study
Sociality has brought many advantages to various hymenoptera species, including their ability
of regulating physical factors in their nest (e.g., temperature). Although less studied,
humidity is known to be important for egg, larval and pupal development, and also for nectar
concentration. Two subspecies of Apis mellifera of the M evolutionary lineage were used as
models to test the ability of a superorganism (i.e. honeybee colony) to regulate the humidity
in its nest (i.e. âhygroregulation hypothesisâ) in four conservation centers: two in France (A.
m. mellifera) and two in Portugal (A. m. iberiensis). We investigated the ability of both subspecies
to regulate the humidity in hives daily, but also during the seasons for one complete
year. Our data and statistical analysis demonstrated the capacity of the bees to regulate
humidity in their hive, regardless of the day, season or subspecies. Furthermore, the study
showed that humidity in beehives is stable even during winter, when brood is absent, and
when temperature is known to be less stable in the beehives. These results suggest that
humidity is important for honeybees at every life stage, maybe because of the âimprintâ of the
evolutionary history of this hymenopteran lineage.This work was supported in part by the
research project BEEHOPE funded by the European
call for projects 2013-2014 BiodivERsA / FACCEJPI
from research agencies of France (ANR-14-
EBID-0001), Spain (PCIN-2014-090) and Portugal
(BiodivERsA /0002/2014). I. Eouzan is financed by
a doctoral grant from the Ministry of National Education, Higher Education and Research (France).info:eu-repo/semantics/publishedVersio
BEEHOPE: um projeto de conservação das subespécies nativas de abelha da Europa Ocidental (linhagem M) à escala Europeia
O projeto BEEHOPE, com o tĂtulo original âHoneybee conservation centres in western Europe - an innovative strategy using sustainable beekeeping to reduce honeybee declineâ, foi um dos 10 aprovados na ĂĄrea da biodiversidade do 5Âș concurso transnacional (2013-2014) BiodivErsA/FACCE-JPI (http://www.biodiversa.org/766), subordinado ao tema âPromover sinergias e reduzir o compromisso entre o abastecimento de alimentos, biodiversidade e serviços dos ecossistemasâ. A diversidade nativa das populaçÔes de abelha melĂfera (Apis mellifera) da linhagem da Europa ocidental (M) tem vindo a ser crescentemente ameaçada pela introdução massiva de colĂłnias da linhagem da Europa oriental (C, onde se incluem as subespĂ©cies A. m. ligustica, A. m. carnica, A. m. macedĂłnica etc.), e tambĂ©m por outros fatores biĂłticos (Varroa e vĂrus associados, Nosema etc.) e abiĂłticos (pesticidas, perda e fragmentação de habitat, alteraçÔes climĂĄticas etc.). Ă neste contexto que surge o projeto BEEHOPE, o qual tem por objetivo Ășltimo contribuir para a conservação da diversidade genĂ©tica das populaçÔes de abelha melĂfera da linhagem M.info:eu-repo/semantics/publishedVersio
Assessing the Diversity and Specificity of Two Freshwater Viral Communities through Metagenomics
Transitions between saline and fresh waters have been shown to be infrequent for microorganisms. Based on host-specific interactions, the presence of specific clades among hosts suggests the existence of freshwater-specific viral clades. Yet, little is known about the composition and diversity of the temperate freshwater viral communities, and even if freshwater lakes and marine waters harbor distinct clades for particular viral sub-families, this distinction remains to be demonstrated on a community scale
The Molecular Diversity of Freshwater Picoeukaryotes Reveals High Occurrence of Putative Parasitoids in the Plankton
Eukaryotic microorganisms have been undersampled in biodiversity studies in freshwater environments. We present an original 18S rDNA survey of freshwater picoeukaryotes sampled during spring/summer 2005, complementing an earlier study conducted in autumn 2004 in Lake Pavin (France). These studies were designed to detect the small unidentified heterotrophic flagellates (HF, 0.6â5 ”m) which are considered the main bacterivores in aquatic systems. Alveolates, Fungi and Stramenopiles represented 65% of the total diversity and differed from the dominant groups known from microscopic studies. Fungi and Telonemia taxa were restricted to the oxic zone which displayed two fold more operational taxonomic units (OTUs) than the oxycline. Temporal forcing also appeared as a driving force in the diversification within targeted organisms. Several sequences were not similar to those in databases and were considered as new or unsampled taxa, some of which may be typical of freshwater environments. Two taxa known from marine systems, the genera Telonema and Amoebophrya, were retrieved for the first time in our freshwater study. The analysis of potential trophic strategies displayed among the targeted HF highlighted the dominance of parasites and saprotrophs, and provided indications that these organisms have probably been wrongfully regarded as bacterivores in previous studies. A theoretical exercise based on a new âparasite/saprotroph-dominated HF hypothesisâ demonstrates that the inclusion of parasites and saprotrophs may increase the functional role of the microbial loop as a link for carbon flows in pelagic ecosystems. New interesting perspectives in aquatic microbial ecology are thus opened
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