Papers by Pieter Visscher
Nature, Aug 1, 1994
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Fems Microbiology Letters, Apr 1, 1992
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Frontiers in Microbiology
The surface of intertidal estuarine sediments is covered with diatom biofilms excreting exopolyme... more The surface of intertidal estuarine sediments is covered with diatom biofilms excreting exopolymeric substances (EPSs) through photosynthesis. These EPSs are highly reactive and increase sediment cohesiveness notably through organo-mineral interactions. In most sedimentary environments, EPSs are partly to fully degraded by heterotrophic bacteria in the uppermost millimeters of the sediment and so they are thought to be virtually absent deeper in the sedimentary column. Here, we present the first evidence of the preservation of EPSs and EPS-mineral aggregates in a 6-m-long sedimentary core obtained from an estuarine point bar in the Gironde Estuary. EPSs were extracted from 18 depth intervals along the core, and their physicochemical properties were characterized by (i) wet chemical assays to measure the concentrations of polysaccharides and proteins, and EPS deprotonation of functional groups, (ii) acid–base titrations, and (iii) Fourier transform infrared spectroscopy. EPS-sediment...
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Goldschmidt2021 abstracts, 2021
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BSGF - Earth Sciences Bulletin, 2021
The Limagne Basin (Massif Central, France) originated during a major, European-scale, extensive e... more The Limagne Basin (Massif Central, France) originated during a major, European-scale, extensive event (European Cenozoic Rift System), which led to the formation of several rift systems in the foreland of the Alps between the Upper Eocene and Pliocene. A fluvio-lacustrine system emplaced in the basin and resulted in a mixed carbonate-siliciclastic sedimentation in which microbial and metazoan buildups occupy an important place. However, microbial deposits are not exclusive to the Cenozoic history of the Limagne Basin; nowadays, in the basin, they still form in association with thermal spring systems. A fieldtrip was carried out in the Limagne Basin as part of the Microbialites: formation, evolution and diagenesis (M-Fed) meeting (October 2019). The objective of this excursion was to assess the diversity of modern and fossil (Chattian to Aquitanian) microbial sediments and structures in three prime locations (the Jussat and Chadrat outcrops and the Grand Gandaillat quarry). A detaile...
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Chemical Geology, 2020
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Shark Bay, Australia, harbours one of the most extensive and diverse systems of living microbial ... more Shark Bay, Australia, harbours one of the most extensive and diverse systems of living microbial mats, that are proposed to be analogs of some of the earliest ecosystems on Earth. These ecosystems have been shown to possess a substantial abundance of uncultivable microorganisms. These enigmatic groups - ‘microbial dark matter’ (MDM) - are hypothesised to play key roles in microbial mats. We reconstructed 115 metagenome-assembled genomes (MAGs) affiliated to MDM, spanning 42 phyla within the bacterial and archaeal domains. We classified bacterial MDM from the PVC group, FCB group, Microgenomates, Parcubacteria, and Peregrinibacteria, as well as a high proportion of archaeal MDM under the TACK, DPANN, Altiarchaeales, and Asgard archaea. The latter includes the first putative Heimdallarchaeota MAG obtained from any microbial mat system. This study reports novel microorganisms (Zixibacterial order GN15) putatively taking part in dissimilatory sulfate reduction in surface hypersaline set...
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29th International Meeting on Organic Geochemistry, 2019
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Global and Planetary Change, 2020
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Frontiers in Microbiology, 2019
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Biogeosciences Discussions, 2016
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Scientific reports, 2015
Microbialites are sedimentary deposits formed by the metabolic interactions of microbes and their... more Microbialites are sedimentary deposits formed by the metabolic interactions of microbes and their environment. These lithifying microbial communities represent one of the oldest ecosystems on Earth, yet the molecular mechanisms underlying the function of these communities are poorly understood. In this study, we used comparative metagenomic and metatranscriptomic analyses to characterize the spatial organization of the thrombolites of Highborne Cay, The Bahamas, an actively forming microbialite system. At midday, there were differences in gene expression throughout the spatial profile of the thrombolitic mat with a high abundance of transcripts encoding genes required for photosynthesis, nitrogen fixation and exopolymeric substance production in the upper three mm of the mat. Transcripts associated with denitrification and sulfate reduction were in low abundance throughout the depth profile, suggesting these metabolisms were less active during midday. Comparative metagenomics of the...
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Chemical Geology, 2021
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Extremophiles, 2014
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Geosciences
The role of culture conditions on the production of exopolymeric substances (EPS) by Synechococcu... more The role of culture conditions on the production of exopolymeric substances (EPS) by Synechococcus strain PCC7942 was investigated. Carbonate mineral precipitation in these EPS was assessed in forced precipitation experiments. Cultures were grown in HEPES-buffered medium and non-buffered medium. The pH of buffered medium remained constant at 7.5, but in non-buffered medium it increased to 9.5 within a day and leveled off at 10.5. The cell yield at harvest was twice as high in non-buffered medium than in buffered medium. High molecular weight (>10 kDa) and low molecular weight (3–10 kDa) fractions of EPS were obtained from both cultures. The cell-specific EPS production in buffered medium was twice as high as in non-buffered medium. EPS from non-buffered cultures contained more negatively charged macromolecules and more proteins than EPS from buffered cultures. The higher protein content at elevated pH may be due to the induction of carbon-concentrating mechanisms, necessary to pe...
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Communications Earth & Environment, 2020
The earliest evidence of life captured in lithified microbial mats (microbialites) predates the o... more The earliest evidence of life captured in lithified microbial mats (microbialites) predates the onset of oxygen production and yet, modern oxygenic mats are often studied as analogs based on their morphological similarity and their sedimentological and biogeochemical context. Despite their structural similarity to fossil microbialites, the presence of oxygen in most modern microbial mats disqualifies them as appropriate models for understanding early Earth conditions. Here we describe the geochemistry, element cycling and lithification potential of microbial mats that thrive under permanently anoxic conditions in arsenic laden, sulfidic waters feeding Laguna La Brava, a hypersaline lake in the Salar de Atacama of northern Chile. We propose that these anoxygenic, arsenosulfidic, phototrophic mats are a link to the Archean because of their distinctive metabolic adaptations to a reducing environment with extreme conditions of high UV, vast temperature fluctuations, and alkaline water i...
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Papers by Pieter Visscher