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Endospore-forming bacteria as new proxies to assess impact of eutrophication in Lake Geneva, (Switzerland-France)

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Wunderlin Tina, Corella Juan Pablo, Junier Thomas, Bueche M., Loizeau Jean-Luc, Giradclos Steffanie, Junier Pilar,
Project Metabolic capabilities of spore-forming microorganisms
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Original article (peer-reviewed)

Journal Aquatic Sciences
Title of proceedings Aquatic Sciences
DOI DOI 10.1007/s00027-013-0329-0

Abstract

Measurements of chemical composition and biological parameters of sediment cores are used as proxies for changes in past environmental conditions and more recently the human impact on ecosystem health. In this study, endospore-forming bacteria are proposed as a new biological proxy for such paleoecological reconstructions. A sediment core providing a record for the past 90 years (137Cs and magnetic susceptibility dating) was retrieved from the Rhone delta of Lake Geneva. X-ray fluorescence was analyzed at a 0.2 cm resolution while DNA extracts, elemental geochemistry and grain size were obtained every four cm intervals. The total number of bacteria and endospore-forming bacteria were quantified by qPCR using the 16S rRNA gene and the endosporulation-specific spo0A gene. Furthermore, a spo0A fragment was subjected to amplicon sequencing to define OTUs and the phylogenetic affiliation of the endospore-formers. The results showed that despite the fact that the quantity of extracted DNA decreased with age of the sediment, the abundance of endospore-forming bacteria remained constant. However, the diversity of this group of bacteria changed significantly reflecting the eutrophication of the lake from 1960 to 1990. The shift in the community composition was linked to the dominance of anaerobic Clostridia-like endospore-formers. This trend has reversed in the last ten years of the record, suggesting a recovery after perturbation. This study shows that the abundance and diversity of endospore-forming bacteria can be used as proxies to reconstruct lake history. We hereby successfully introduce a new strategy for paleoecology that could also be applied to ocean sediments and long sediment cores.
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