Les arrels de certes plantes seleccionen els microorganismes que les colonitzen

Els aiguamolls són ambients de gran biodiversitat, vàlua ambiental i importància hídrica que juguen un paper rellevant en l'ecosistema. La vegetació d'aquests ambients són plantes aquàtiques a les arrels de les quals viuen microorganismes que, per exemple, poden regular el seu desenvolupament i modificar la circulació de nutrients en els sediments del voltant. Un estudi realitzat per investigadors de la UAB i de la Universitat de Girona en col·laboració amb la Estació Biològica de Doñana posa de manifest que les arrels de certes espècies tenen un efecte seleccionador sobre les comunitats de microorganismes.Wetlands are environments of high biodiversity, environmental value and water importance that play a relevant role in the ecosystem. The vegetation in these environments consists of aquatic plants in whose roots microorganisms live which, for example, can regulate their development and modify the circulation of nutrients in the surrounding sediments. A study conducted by researchers of the UAB and the University of Girona in cooperation with the Doñana Biological Station shows that the roots of certain species have a selecting effect on the communities of microorganisms.Los humedales son ambientes de gran biodiversidad, valía ambiental e importancia hídrica que juegan un papel relevante en el ecosistema. La vegetación de estos ambientes son plantas acuáticas en cuyas raíces viven microorganismos que, por ejemplo, pueden regular su desarrollo y modificar la circulación de nutrientes en los sedimentos de los alrededores. Un estudio realizado por investigadores de la UAB y de la Universitat de Girona en colaboración con la Estación Biológica de Doñana pone de manifiesto que las raíces de ciertas especies tienen un efecto seleccionador sobre las comunidades de microorganismos

Les arrels de certes plantes seleccionen els microorganismes que les colonitzen

Els aiguamolls són ambients de gran biodiversitat, vàlua ambiental i importància hídrica que juguen un paper rellevant en l'ecosistema. La vegetació d'aquests ambients són plantes aquàtiques a les arrels de les quals viuen microorganismes que, per exemple, poden regular el seu desenvolupament i modificar la circulació de nutrients en els sediments del voltant. Un estudi realitzat per investigadors de la UAB i de la Universitat de Girona en col·laboració amb la Estació Biològica de Doñana posa de manifest que les arrels de certes espècies tenen un efecte seleccionador sobre les comunitats de microorganismes.Wetlands are environments of high biodiversity, environmental value and water importance that play a relevant role in the ecosystem. The vegetation in these environments consists of aquatic plants in whose roots microorganisms live which, for example, can regulate their development and modify the circulation of nutrients in the surrounding sediments. A study conducted by researchers of the UAB and the University of Girona in cooperation with the Doñana Biological Station shows that the roots of certain species have a selecting effect on the communities of microorganisms.Los humedales son ambientes de gran biodiversidad, valía ambiental e importancia hídrica que juegan un papel relevante en el ecosistema. La vegetación de estos ambientes son plantas acuáticas en cuyas raíces viven microorganismos que, por ejemplo, pueden regular su desarrollo y modificar la circulación de nutrientes en los sedimentos de los alrededores. Un estudio realizado por investigadores de la UAB y de la Universitat de Girona en colaboración con la Estación Biológica de Doñana pone de manifiesto que las raíces de ciertas especies tienen un efecto seleccionador sobre las comunidades de microorganismos

Resolent els misteris de la Terra : els grans dipòsits sedimentaris de ferro tindrien el seu origen en el plàncton dels oceans primitius

La cubeta de Kabuno, al nord del llac Kivu, en ple centre d'Àfrica (República Democràtica del Congo), permet viatjar en el temps i fer una ullada a com eren els oceans primitius i com l'activitat d'uns microorganismes va generar, ara fa milions d'anys, els enormes dipòsits de ferro existents a la Terra. Gairebé un terç del bacterioplàncton d'aquesta cubeta lacustre oxida ferro utilitzant la llum en un tipus de fotosíntesi sense oxigen que es creu que era la predominant a la terra primitiva durant bilions d'anys.La cubeta de Kabuno, al norte del lago Kivu, en pleno centro de África (República Democrática del Congo), permite viajar en el tiempo y echar un vistazo a cómo eran los océanos primitivos y cómo la actividad de unos microorganismos generó, hace millones de años, los enormes depósitos de hierro existentes en la Tierra. Casi un tercio del bacterioplancton de esta cubeta lacustre oxida hierro utilizando la luz en un tipo de fotosíntesis sin oxígeno que se cree que era la predominante en la tierra primitiva durante billones de años.Kabuno bay, located in the north of Lake Kivu, in the heart of Africa (Democratic Republic of the Congo) offers a glimpse into the early oceans, showing how a tiny group of microbes developed the biggest iron deposits on Earth. Nearly one third of the microbes present in this freshwater basin grow by performing a different kind of photosynthesis by iron oxidation. It is believed that this kind of photosynthesis was the predominant on the early Earth over billions of years

Diversity, dynamics and activity of mesophilic Archaea in stratified feshwater lakes. Implications in biogeochemical cycles

Aquesta tesi doctoral va estudiar la diversitat (riquesa i abundància), la distribució i la dinàmica de les comunitats planctòniques d'Archaea presents a diferents llacs estratificats temperats d'aigua dolça per aportar evidencies sobre la seva distribució i la seva possible activitat en aquests ecosistemes en relació als cicles biogeoquímics presents en els mateixos. Es varen estudiar dos estanyols d'origen càrstic (l'Estanyol del Vilar durant cinc anys consecutius (2001-2005) i l'Estanyol de Can Coromina) i un llac d'origen volcànic (Llac Kivu) analitzant, per una banda, la seva comunitat planctònica d'Archaea mitjançant una aproximació molecular i, per una altra, la seva possible activitat en aquests ambients (p.e., la nitrificació i la fixació de carboni). Per contextualitzar els resultats, es va realitzar un anàlisi in silico dels patrons de distribució global dels Archaea mesòfils mitjançant un anàlisi a nivell de llinatge combinant seqüències del gen 16S rRNA amb diferents eines estadístiques i d'ecologia general.The present PhD thesis analysed the diversity (richness and evenness), distribution and dynamics of planktonic Archaea in several temperate stratified freshwater lakes to shed some light on their distribution and potential activity in these ecosystems in relation to prevalent biogeochemical cycles. In this sense, two karstic lagoons (Lake Vilar during five consecutive years (2001-2005) and Coromina lagoon) and a volcanic lake (Lake Kivu) were studied analysing, in the one hand, their archaeal planktonic community throughout a molecular approach and, in the other hand, their potential acitivity in these environments (e.g., nitrification and carbon fixation). In order to contextualize the obtained results, an in silico phylogenetic lineage-based analysis on the global distribution of lacustrine Archaea was conducted using 16S rRNA gene sequences in combination with statistical and general ecology tools

High archaeal richness in the water column of a freshwater sulfurous karstic lake along an interannual study.

12 páginas, 2 tablas, 5 figures.We surveyed the archaeal assemblage in a stratified sulfurous lake (Lake Vilar, Banyoles, Spain) over 5 consecutive years to detect potential seasonal and interannual trends in the free-living planktonic Archaea composition. The combination of different primer pairs and nested PCR steps revealed an unexpectedly rich archaeal community. Overall, 140 samples were analyzed, yielding 169 different 16S rRNA gene sequences spread over 14 Crenarchaeota (109 sequences) and six Euryarchaeota phylogenetic clusters. Most of the Crenarchaeota (98% of the total crenarchaeotal sequences) affiliated within the Miscellaneous Crenarchaeota Group (MCG) and were related to both marine and freshwater phylotypes. Euryarchaeota mainly grouped within the Deep Hydrothermal Vent Euryarchaeota (DHVE) cluster (80% of the euryarchaeotal sequences) and the remaining 20% distributed into three less abundant taxa, most of them composed of soil and sediment clones. The largest fraction of phylotypes from the two archaeal kingdoms (79% of the Crenarchaeota and 54% of the Euryarchaeota) was retrieved from the anoxic hypolimnion, indicating that these cold and sulfide-rich waters constitute an unexplored source of archaeal richness. The taxon rank-frequency distribution showed two abundant taxa (MCG and DHVE) that persisted in the water column through seasons, plus several rare ones that were only detected occasionally. Differences in richness distribution and seasonality were observed, but no clear correlations were obtained when multivariate statistical analyses were carried out.This study was funded through projects VIARC (Ref. REN 2003-08333-GLO) and CRENYC (Ref. CGL2006-12058-BOS) to C.M.B. and E.O.C. from the Spanish Ministerio de Educación y Ciencia (MEC). M.L. is recipient of a PhD student fellowship (BES-2004-5127) from the Spanish MEC.Peer reviewe

Chemoautotrophy and anoxygenic photosynthesis within the water column of a large meromictic tropical lake (Lake Kivu, East Africa)

We quantified chemoautotrophic and anoxygenic photosynthetic microbial production in the water column of Lake Kivu, a permanently stratified tropical lake situated amidst volcanic activity, and aimed to identify the microorganisms involved in these processes through the analysis of their phospholipid fatty acid (PLFA) content and stable isotope (13C) labelling of PLFA in a set of incubation experiments. Data demonstrate the existence of a biogeochemically active chemoautotrophic bacterial community in the redoxcline of Lake Kivu (50–70 m). PLFA data indicate that the bacterial communities are structured vertically in the water column, with a large dissimilarity between the oxic and anoxic waters. Maximum volumetric dark CO2 fixation rates measured in Lake Kivu were in the same range as values reported from H2S-rich marine redoxclines, such as the Black and Baltic Seas, and the Cariaco Basin. Similarly, maximal chemoautotrophic activities in Lake Kivu were observed in sulfidic waters, just below the oxycline. Anoxygenic photosynthetic production was never observed in the main basin of Lake Kivu. However, anoxygenic phototrophs largely dominated CO2 fixation in the illuminated redoxcline of Kabuno Bay, a shallower ferruginous sub-basin. Overall, this study supports the idea that chemoautotrophs and/or anoxygenic photoautotrophs might play an important role in the flow of carbon and energy in permanently stratified tropical ecosystems. In Lake Kivu, these processes significantly contribute to organic matter biosynthesis and exert an indirect control on oxygenic photoautotrophs by shortcircuiting the vertical transport of nutrients to the illuminated and oxygenated surface waters.AFRIVA

Microcosm experiments of oil degradation by microbial mats. II. The changes in microbial species

11 pages, 2 tables, 4 figures.The influence of microbial mats on the degradation of two crude oils (Casablanca and Maya) and the effect of oil pollution on the mat structure were assessed using model ecosystems, prepared under laboratory conditions subject to tidal movements, from pristine Ebro Delta microbial-mat ecosystems. Both selected oils are examples of those currently used for commercial purposes. Casablanca crude oil is aliphatic with a low viscosity; Maya represents a sulphur-rich heavy crude oil that is predominantly aromatic. In the unpolluted microcosms, Microcoleus chthonoplastes-, Phormidium- and Oscillatoria-like were the dominant filamentous cyanobacterial morphotypes, whilst Synechoccocus-, Synechocystis- and Gloeocapsa-like were the most abundant unicellular cyanobacteria. After oil contamination, no significant changes of chlorophyll a and protein concentrations were observed, though cyanobacterial diversity shifts were monitored. Among filamentous cyanobacteria, M. chthonoplastes-like morphotype was the most resistant for both oils, unlike the other cyanobacteria, which tolerated Casablanca but not Maya. Unicellular cyanobacteria seemed to be resistant to pollution with both essayed oils, with the exception of the morphotype resembling Gloeocapsa, which was sensitive to both oils. The crude-oil addition also had a significant effect on certain components of the heterotrophic microbial community. Casablanca oil induced an increase in anaerobic heterotrophic bacteria, whereas the opposite effect was observed in those heterotrophs when polluted with Maya oil. The overall results, microbiological and crude-oil transformation analysis, indicate that the indigenous community has a considerable potential to degrade oil components by means of the metabolic cooperation of phototrophic and heterotrophic populationWe would like to thank the Salines de la Trinitat and Parc Natural del Delta de l’Ebre (Generalitat de Catalunya) for permission to access the sampling site, and REPSOL-YPF for providing samples of Casablanca and Maya crude oils. We also thank members of the Servei de Microscòpia at the Autonomous University of Barcelona (UAB) for support with CLSM. We are grateful to Lidia Hernandez and Carol Egea for technical assistance with the microcosms and sample processing. This research was funded by the European Union MATBIOPOL project EVK3-CT-1999-00010.Peer reviewe

Maintenance of previously uncultured freshwater archaea from anoxic waters under laboratory conditions

6 páginas, 2 figuras, 2 tablas.Culture conditions for the maintenance of previously uncultured members of the Archaea thriving in anoxic water layers of stratified freshwater lakes are described. The proposed enrichment conditions, based on the use of defined medium composition and the maintenance of anoxia, have been proven effective for the maintenance of the archaeal community with virtually no changes over time for periods up to 6 months as revealed by a PCR-DGGE analysis. Phylotypes belonging to groups poorly represented in culture collections such as the DeepSea Hydrothermal Vent Euryarchaeota (DHVE) and the Miscellaneous Crenarchaeotic Group (MCG) were maintained and selectively enriched when compared to the correspondent indigenous planktonic archaeal community.This work was supported by coordinated projects REN2003-08333 and CRENYC CGL2006-12058 from the Spanish Ministerio de Educación y Ciencia (MEC) to CMB and EOC.Peer reviewe

Contribution of deep dark fixation processes to overall CO2 incorporation and large vertical changes of microbial populations in stratified karstic lakes.

15 páginas, 7 figuras, 2 tablas.We carried out a detailed study in five stratified lakes in the karstic regions of NE Spain along a redox gradient combining vertical profiles of inorganic carbon dioxide fixation and analysis of microbial (bacteria and archaea) community composition determined by 16S rRNA gene fingerprinting (DGGE), microscopic counts, and pigment analysis. High rates of non-photosynthetic (i.e., ‘‘dark’’) inorganic carbon incorporation were detected mostly at deeper layers after short-term in situ incubations at noon. Significant contribution of dark CO2 incorporation was observed at the whole lake level for the single time sampling, ranging between 4 and 19% of total carbon fixation measured, and up to 31% in the case of a meromictic basin. Good agreement was found between vertical patterns in redox conditions and the different microbial diversity descriptors (DGGE band sequencing, microscopic analysis, and pigment data), showing large vertical changes in microbial community composition covering a wide range of phylogenetic diversity. Cyanobacteria, Alpha and Beta-Proteobacteria, Actinobacteria, Flavobacteria and Flectobacillaceae were the most frequently recovered groups in the DGGE from oxygenated water masses. In anoxic waters, we found Beta-Proteobacteria mostly of the Rhodoferax group, Gamma-Proteobacteria (Chromatiaceae), Delta-Proteobacteria related to different sulfate reducing bacteria, Chlorobiaceae, and anaerobic Bacteroidetes spread among the Bacteroidales, Flavobacteriales and Saprospiraceae. However, as a whole, we did not find any significant correlation between dark fixation rates and either nutrient distribution and microbial community composition in the study lakes. All of this suggests that (1) different physiologies and ecologies are simultaneously contributing to the process (2) more sensitive methods are needed and more specific compounds measured and (3) some of the non-specialist microbial populations detected may carry out carbon dioxide assimilation in the dark under in situ conditions.This research was supported by projects VIARC REN2003-08333 and CRENYC CGL2006-12058 to EOC and CBM, from the Spanish Ministerio de Ciencia e Innovacio´n (MICINN), and CONSOLIDER-INGENIO 2010 project GRACCIE CSD2007-00067 from MICINN.Peer reviewe