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Auteur (up) Auguet, J.C.; Montanie, H.; Hartmann, H.J.; Lebaron, P.; Casamayor, E.O.; Catala, P.; Delmas, D.
Titre Potential effect of freshwater virus on the structure and activity of bacterial communities in the Marennes-Oleron Bay (France) Type Article scientifique
Année 2009 Publication Revue Abrégée Microb Ecol
Volume 57 Numéro 2 Pages 295-306
Mots-Clés 16S/genetics Seasons Seawater/microbiology/virology Viruses/*growth & development *Water Microbiology; Bacteria/genetics/*growth & development/*virology Biodiversity Colony Count; Bacterial/genetics France Fresh Water/virology Polymorphism; Microbial DNA Fingerprinting DNA; Ribosomal; Single-Stranded Conformational Population Dynamics RNA
Résumé Batch culture experiments using viral enrichment were conducted to test the response of a coastal bacterial community to autochthonous (i.e., co-existing) or allochthonous riverine viruses. The effects of viral infections on bacterial dynamics and activity were assessed by epifluorescence microscopy and thymidine incorporation, respectively, whereas the effect of viral infection on bacterial community composition was examined by polymerase chain reaction-single strand conformation polymorphism 16S ribosomal RNA fingerprinting. The percentages of high nucleic acid-containing cells, evaluated by flow cytometry, were significantly correlated (r2=0.91, n=12, p<0.0001) to bacterial production, making this value a good predictor of active cell dynamics along the study. While confinement and temperature were the two principal experimental factors affecting bacterial community composition and dynamics, respectively, additions of freshwater viruses had significant effects on coastal bacterial communities. Thus, foreign viruses significantly reduced net bacterial population increase as compared to the enrichment treated with inactivated virus. Moreover, freshwater viruses recurrently and specifically affected bacterial community composition, as compared to addition of autochthonous viruses. In most cases, the combined treatment viruses and freshwater dissolved organic matter helped to maintain or even enhance species richness in coastal bacterial communities in agreement to the 'killing the winner' hypothesis. Thus, riverine virus input could potentially influence bacterial community composition of the coastal bay albeit with modest modification of bulk bacterial growth.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1301
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Auteur (up) Auguet, J.C.; Montanie, H.; Lebaron, P.
Titre Structure of virioplankton in the Charente Estuary (France): transmission electron microscopy versus pulsed field gel electrophoresis Type Article scientifique
Année 2006 Publication Revue Abrégée Microb Ecol
Volume 51 Numéro 2 Pages 197-208
Mots-Clés Capsid/chemistry *Electrophoresis; Electron Plankton Rivers/*virology Seasons Seawater/*microbiology/*virology Viruses/genetics/*isolation & purification/ultrastructure *Water Microbiology; Gel; Pulsed-Field Environmental Monitoring/methods France Genome; Viral/genetics *Microscopy
Résumé Changes in the composition of viral communities were investigated along a salinity gradient and at different times by means of transmission electron microscopy (TEM) and pulsed field gel electrophoresis (PFGE). Samples were collected in fresh (Charente River), estuarine (Charente Estuary), and coastal (Pertuis d'Antioche, French Atlantic coast) waters. Both methods revealed similar patterns in viral community structure with a dominance of small viral particles (capsid and genome size). Viruses with a head size below 65 nm made up 71 +/- 5% of total virus-like particles, and virus-like genomes (VLG) below 100 kb accounted for 89 +/- 9% of total VLG. Despite this apparent stability of virioplankton composition over spatial scale (salinity gradient), the occurrence of large viruses (capsid and genome size) in estuarine and seawater samples indicated the presence of viral populations specific to a geographical location. Temporal changes in the structure (capsid and genome size) of viral communities were more pronounced than those reported at the spatial scale. From January to May 2003, seasonal changes in viral abundance and bacterial production occurred concomitantly with an increase in viral genomic diversity (richness), suggesting that virioplankton composition was strongly linked to changes in microbial activity and/or in the structure of the host communities. Although PFGE and TEM yielded complementary results in the description of virioplankton structures, it seems that the use of PFGE alone should be enough for the monitoring of community changes.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1297
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Auteur (up) Boukef, I.; Bejaoui, B.; Hassan, M.B.; Mraouna, R.; Got, P.; Harzallah, A.; Elbour, M.
Titre Spatial distribution and decay rates of coliforms in the sediments and water column of the bizerte lagoon Type Article scientifique
Année 2012 Publication Revue Abrégée Vie Milieu
Volume 62 Numéro 1 Pages 29-36
Mots-Clés bizerte lagoon; coastal waters; contamination; environmental-conditions; escherichia coli decay; estuarine; fecal indicator bacteria; pathogenic bacteria; pollution; recreational waters; seasonal survey; seawater; sunlight; sunlight inactivation; total coliform
Résumé In order to assess the impact of bacterial input loads in Bizerte lagoon (Northern Tunisia), a seasonal survey was done for total coliform bacteria covering the whole lagoon area, to reproduce and prevent dispersion of input loads of terrestrial discharges in the lagoon. Effect of solar radiation on Escherichia coli strains was investigated using seawater microcosms comparatively exposed to sunlight and dark conditions. The results revealed (i) high charges of coliforms in the sediment rather than in the water column, (ii) total coliforms increased periodically with season in both compartments, (iii) anthropogenic discharges influence coastal areas of the lagoon, and (iv) solar radiation has an effect on decay rate of E. coli maintained in microcosm experiments.
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ISSN 0240-8759 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 846
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Auteur (up) Boukef, I.; El Bour, M.; Al Gallas, N.; El Bahri, O.; Mejri, S.; Mraouna, R.; Ben Aissa, R.; Boudabous, A.; Got, P.; Troussellier, M.
Titre Survival of Escherichia coli Strains in Mediterranean Brackish Water in the Bizerte Lagoon in Northern Tunisia Type Article scientifique
Année 2010 Publication Revue Abrégée Water Environ Res
Volume 82 Numéro 11 Pages 2249-2257
Mots-Clés bizerte lagoon; brackish water; coastal waters; cytotoxicity; enteric bacteria; escherichia coli; fecal-coliforms; marine waters; salmonella-typhimurium; seawater microcosms; sewage; shigella-dysenteriae type-1; sunlight; survival; viability; virulence
Résumé This study investigated survival and virulence of Escherichia coli strains exposed to natural conditions in brackish water. Two E. coli strains (O126:B16 and O55:B5) were incubated in water microcosms in the Bizerte lagoon in Northern Tunisia and exposed for 12 days to natural sunlight in June (231 to 386 W/m(2), 26 +/- 1 degrees C, 30 g/L) and in April (227 to 330 W/m(2), 17 +/- 1 degrees C, 27 g/L) or maintained in darkness for 21 days (17 +/- 1 degrees C, 27 g/L). The results revealed that sunlight was the most significant inactivating factor (decrease of 3 Ulog within 48 hours for the two strains) compared to salinity and temperature (in darkness). Survival time of the strains was prolonged as they were maintained in darkness. Local strain (E. coli O55:B5) showed better survival capacity (T(90) = 52 hours) than E. coli O126:B16 (T(90) = 11 h). For both, modifications were noted only for some metabolic activities of carbohydrates hydrolysis. Cytotoxicity of the two strains, tested on Vero cell, was maintained during the period of survival. Water Environ. Res., 82, 2249 (2010).
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ISSN 1061-4303 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 864
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Auteur (up) Lebrato, M.; Wang, Y.V.; Tseng, L.-C.; Achterberg, E.P.; Chen, X.-G.; Molinero, J.-C.; Bremer, K.; Westernstroeer, U.; Soeding, E.; Dahms, H.-U.; Kueter, M.; Heinath, V.; Joehnck, J.; Konstantinou, K.I.; Yang, Y.J.; Hwang, J.-S.; Garbe-Schoenberg, D.
Titre Earthquake and typhoon trigger unprecedented transient shifts in shallow hydrothermal vents biogeochemistry Type Article scientifique
Année 2019 Publication Revue Abrégée Sci Rep
Volume 9 Numéro Pages 16926
Mots-Clés arc; cleaning procedures; fluids; foraminiferal mg/ca; island; kueishantao; ocean acidification; sea; seawater; taiwan
Résumé Shallow hydrothermal vents are of pivotal relevance for ocean biogeochemical cycles, including seawater dissolved heavy metals and trace elements as well as the carbonate system balance. The Kueishan Tao (KST) stratovolcano off Taiwan is associated with numerous hydrothermal vents emitting warm sulfur-rich fluids at so-called White Vents (WV) and Yellow Vent (YV) that impact the surrounding seawater masses and habitats. The morphological and biogeochemical consequences caused by a M5.8 earthquake and a C5 typhoon (“Nepartak”) hitting KST (12th May, and 2nd-10th July, 2016) were studied within a 10-year time series (2009-2018) combining aerial drone imagery, technical diving, and hydrographic surveys. The catastrophic disturbances triggered landslides that reshaped the shoreline, burying the seabed and, as a consequence, native sulfur accretions that were abundant on the seafloor disappeared. A significant reduction in venting activity and fluid flow was observed at the high-temperatureYV. Dissolved Inorganic Carbon (DIC) maxima in surrounding seawater reached 3000-5000 mu mol kg(-1), and Total Alkalinity (TA) drawdowns were below 1500-1000 mu mol kg(-1) lasting for one year. A strong decrease and, in some cases, depletion of dissolved elements (Cd, Ba, Tl, Pb, Fe, Cu, As) including Mg and Cl in seawater from shallow depths to the open ocean followed the disturbance, with a recovery of Mg and Cl to pre-disturbance concentrations in 2018. The WV and YV benthic megafauna exhibited mixed responses in their skeleton Mg:Ca and Sr:Ca ratios, not always following directions of seawater chemical changes. Over 70% of the organisms increased skeleton Mg:Ca ratio during rising DIC (higher CO2) despite decreasing seawater Mg:Ca ratios showing a high level of resilience. KST benthic organisms have historically co-existed with such events providing them ecological advantages under extreme conditions. The sudden and catastrophic changes observed at the KST site profoundly reshaped biogeochemical processes in shallow and offshore waters for one year, but they remained transient in nature, with a possible recovery of the system within two years.
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ISSN 2045-2322 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2663
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