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Irreversible Collective Migration of Cyanobacteria in Eutrophic Conditions

In response to natural or anthropocentric pollutions coupled to global climate changes, microorganisms from aquatic environments can suddenly accumulate on water surface. These dense suspensions, known as blooms, are harmful to ecosystems and signicantly degrade the quality of water resources. In or...

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Autores principales: Dervaux, Julien, Mejean, Annick, Brunet, Philippe
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4370732/
https://www.ncbi.nlm.nih.gov/pubmed/25799424
http://dx.doi.org/10.1371/journal.pone.0120906
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author Dervaux, Julien
Mejean, Annick
Brunet, Philippe
author_facet Dervaux, Julien
Mejean, Annick
Brunet, Philippe
author_sort Dervaux, Julien
collection PubMed
description In response to natural or anthropocentric pollutions coupled to global climate changes, microorganisms from aquatic environments can suddenly accumulate on water surface. These dense suspensions, known as blooms, are harmful to ecosystems and signicantly degrade the quality of water resources. In order to determine the physico-chemical parameters involved in their formation and quantitatively predict their appearance, we successfully reproduced irreversible cyanobacterial blooms in vitro. By combining chemical, biochemical and hydrodynamic evidences, we identify a mechanism, unrelated to the presence of internal gas vesicles, allowing the sudden collective upward migration in test tubes of several cyanobacterial strains (Microcystis aeruginosa PCC 7005, Microcystis aeruginosa PCC 7806 and Synechocystis sp. PCC 6803). The final state consists in a foamy layer of biomass at the air-liquid interface, in which micro-organisms remain alive for weeks, the medium lying below being almost completely depleted of cyanobacteria. These "laboratory blooms" start with the aggregation of cells at high ionic force in cyanobacterial strains that produce anionic extracellular polymeric substances (EPS). Under appropriate conditions of nutrients and light intensity, the high photosynthetic activity within cell clusters leads the dissolved oxygen (DO) to supersaturate and to nucleate into bubbles. Trapped within the EPS, these bubbles grow until their buoyancy pulls the biomass towards the free surface. By investigating a wide range of spatially homogeneous environmental conditions (illumination, salinity, cell and nutrient concentration) we identify species-dependent thresholds and timescales for bloom formation. We conclude on the relevance of such results for cyanobacterial bloom formation in the environment and we propose an ecient method for biomass harvesting in bioreactors.
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spelling pubmed-43707322015-04-04 Irreversible Collective Migration of Cyanobacteria in Eutrophic Conditions Dervaux, Julien Mejean, Annick Brunet, Philippe PLoS One Research Article In response to natural or anthropocentric pollutions coupled to global climate changes, microorganisms from aquatic environments can suddenly accumulate on water surface. These dense suspensions, known as blooms, are harmful to ecosystems and signicantly degrade the quality of water resources. In order to determine the physico-chemical parameters involved in their formation and quantitatively predict their appearance, we successfully reproduced irreversible cyanobacterial blooms in vitro. By combining chemical, biochemical and hydrodynamic evidences, we identify a mechanism, unrelated to the presence of internal gas vesicles, allowing the sudden collective upward migration in test tubes of several cyanobacterial strains (Microcystis aeruginosa PCC 7005, Microcystis aeruginosa PCC 7806 and Synechocystis sp. PCC 6803). The final state consists in a foamy layer of biomass at the air-liquid interface, in which micro-organisms remain alive for weeks, the medium lying below being almost completely depleted of cyanobacteria. These "laboratory blooms" start with the aggregation of cells at high ionic force in cyanobacterial strains that produce anionic extracellular polymeric substances (EPS). Under appropriate conditions of nutrients and light intensity, the high photosynthetic activity within cell clusters leads the dissolved oxygen (DO) to supersaturate and to nucleate into bubbles. Trapped within the EPS, these bubbles grow until their buoyancy pulls the biomass towards the free surface. By investigating a wide range of spatially homogeneous environmental conditions (illumination, salinity, cell and nutrient concentration) we identify species-dependent thresholds and timescales for bloom formation. We conclude on the relevance of such results for cyanobacterial bloom formation in the environment and we propose an ecient method for biomass harvesting in bioreactors. Public Library of Science 2015-03-23 /pmc/articles/PMC4370732/ /pubmed/25799424 http://dx.doi.org/10.1371/journal.pone.0120906 Text en © 2015 Dervaux et al http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Dervaux, Julien
Mejean, Annick
Brunet, Philippe
Irreversible Collective Migration of Cyanobacteria in Eutrophic Conditions
title Irreversible Collective Migration of Cyanobacteria in Eutrophic Conditions
title_full Irreversible Collective Migration of Cyanobacteria in Eutrophic Conditions
title_fullStr Irreversible Collective Migration of Cyanobacteria in Eutrophic Conditions
title_full_unstemmed Irreversible Collective Migration of Cyanobacteria in Eutrophic Conditions
title_short Irreversible Collective Migration of Cyanobacteria in Eutrophic Conditions
title_sort irreversible collective migration of cyanobacteria in eutrophic conditions
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4370732/
https://www.ncbi.nlm.nih.gov/pubmed/25799424
http://dx.doi.org/10.1371/journal.pone.0120906
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