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Poster De Conférence Année : 2014

Spatial and temporal variation of microbial diversity in river biofilms

Résumé

Proliferations of benthic cyanobacteria in shallow rivers can be hazardous to the human and animal health due to the ability of some species to produce neurotoxins such as anatoxins. In the last ten years, they have been involved in the death of numerous dogs all around the world but despite that, few studies have been performed on the development of biofilms dominated by cyanobacteria in rivers and on the environmental conditions promoting their proliferation. Within biofilms, cyanobacteria coexist with a large diversity of microorganisms such as diatoms, green algae and other bacteria. To get further insight on biofilm installation and development particularly concerning the environmental conditions leading to the dominance of cyanobacteria in these complex communities, we have monitored cyanobacterial biofilms during one summer in different sampling sites along a French river. Four sampling sites along the Loue river were studied at four different dates during the bloom period (June to September). The relative abundances of cyanobacteria, diatoms and green algae was estimated by microscopic counts and the biomasses of all the primary producers by the measurements of chlorophyll-a concentrations. The genetic structure of bacterial communities was assessed using a 454 pyrosequencing approach targeting a fragment of the 16S rRNA gene. Then, the evolution of the bacterial communities was analyzed in relation to the environmental conditions (such as flow, temperature, pH, stone size) and to the biofilm biomass. First, we found that biofilms in the Loue river were mainly dominated by an association of diatoms and cyanobacteria. Second, it appeared that the bacterial communities associated to these autotrophic organisms were highly diversified with a predominance of proteobacteria, in particular alphaproteobacteria. Surprisingly, it appeared also that among these alphaproteobacteria, most of the reads were related to the Rhodobacter genus, which are also photosynthetic microorganisms that may contribute significantly to primary production. Finally, it seems that the relative importance of cyanobacteria and Rhodobacter are determined by environmental factors such as water temperature or flow velocity. If the primary producers of benthic biofilms of the Loue river are dominated for their eukaryotic part by diatoms, it appears that for the prokaryote part, depending on the environmental conditions, cyanobacteria and Rhodobacter can be the dominant microorganisms. We are performing analyses on our data set in the goal to determine if preferential associations between species can be highlighted. Moreover, further studies in other rivers will precise the environmental conditions that lead to the dominance of cyanobacteria in biofilms and the production of toxins by these microorganisms.
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Dates et versions

hal-04080951 , version 1 (25-04-2023)

Identifiants

  • HAL Id : hal-04080951 , version 1

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Anouk Zancarini, Isidora Echenique-Subiabre, Didier Debroas, Catherine Quiblier, Jean-François Humbert. Spatial and temporal variation of microbial diversity in river biofilms. ISME15, Aug 2014, Seoul, South Korea. ⟨hal-04080951⟩
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