Biology subjects

Perriere, F.

Publications and source records attributed to Perriere, F..

4 recordsLinked to original sources

bioRxiv2025

Long lasting non-cellular reactions in sterile soils recapitulates most of the intermediates of the Krebs cycle

Over the past decade, chemical evidence has emerged that non-enzymatic metabolic pathways, such as the Krebs cycle, may have existed before cellular life on the primitive Earth. However, the question of whether non-cellular reactions analogous to cell respiration metabolism are still "active" in todays biosphere and whether they contribute to CO2 emissions in contemporary ecosystems remains open. In the present study, we investigated the long-term fate (> 6 months) of organic substrates supplied in sterilised soils in which cell life was not detectable. Through a series of analytical studies performed on the water-extractable fraction of soil exometabolites using chromatography, mass spectrometry and isotope labelling, we demonstrate that sterile soil matrix incubated with [13C6]-glucose and [13C6]-citrate can spontaneously generate intermediates of the Krebs cycle, alongside by-products such as acetate and formate. These findings support the hypothesis that extracellular metabolisms (EXOMETs) form a network of non-cellular reactions resembling metabolic pathways involved in aerobic respiration and anaerobic fermentation of cells. This research not only provides insights into the chemical continuity between chemistry and biochemistry but also raises questions about the implications of non-cellular pathways for soil ecosystem functioning and carbon fluxes in the contemporary biosphere.

biochemistry↗

bioRxiv2025

Non-living respiration: another breath in the soil?

The present study challenges the traditional view that respiration of organic carbon to CO2 is exclusively an intracellular process, revealing that organic compound respiration can occur spontaneously in an extracellular context in soils. Using 1H nuclear magnetic resonance spectroscopy to analyse the dynamics of the sterile soil exometabolomes alongside C-CO2 flux analyses and sterile soil fuel cells, we show that soil catalysts facilitate a diverse array of substrate-driven reactions, leading to the complete oxidation of organic compounds to CO2 with O2 consumption. Our results indicate that soil particles are capable of transferring electrons from substrates to the final acceptor, sustaining metabolic processes independently of living cells. Notably, some soil catalysts and induced respiration remain stable for over six years. Our results support the coexistence of cellular and non-cellular metabolic pathways in soil respiration.

ecology↗

bioRxiv2025

Temperature dependent response of microcystin-LR in acclimated Microcystis aeruginosa: highest content expected near the growth optimum

As climate change raises global temperatures and increases the frequency of cyanobacterial blooms, understanding how rising mean temperatures affect cyanotoxin content is crucial. However, no clear consensus exists, and the use of different methodologies, including different units of measurement and experimental conditions could significantly alter the yield of the relationship between temperature and toxins content. In this study, we assessed free microcystin content and cell volume in Microcystis aeruginosa PCC 7806 acclimated to seven temperatures spanning its entire thermal niche. This experimental design firstly highlighted the significant reduction in cell volume with rising temperatures between 17{degrees}C and 29{degrees}C. As a result, when the microcystin concentration was normalized by its cell volume, its temperature response was transformed from a negative correlation to a bell-shaped curve, with higher free MC-LR content measured at an estimated optimum temperature of 26.2{degrees}C, close to the thermal growth optimum of Microcystis aeruginosa. These findings provide new insights into the effects of climate warming on microcystin content. ImportanceMicrocystin-LR is a widespread cyanotoxin, originally known for its liver toxicity. In freshwater environments, cyanotoxins are an increasing concern as harmful cyanobacterial blooms become more frequent with rising global temperatures. Microcystis aeruginosa, a common bloom-forming species found worldwide, is a major producer of microcystin-LR. Understanding how environmental factors such as temperature influence toxin content in this species is essential for predicting bloom toxicity under future climate scenarios. However, current knowledge remains fragmented due to numerous factors that can influence its production and also to different way of measuring toxins and expressing their concentrations (cell or {micro}m3). Confirming that temperature greatly modifies biovolume of M. aeruginosa, this study offers new insights by highlighting the importance of considering cell volume when evaluating toxin content. Integrating changes in cell size helps reconcile earlier conflicting results and contributes to a more accurate understanding of how temperature affects toxin production in cyanobacteria. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=176 HEIGHT=200 SRC="FIGDIR/small/660678v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@7a591org.highwire.dtl.DTLVardef@6eb39org.highwire.dtl.DTLVardef@3d0f19org.highwire.dtl.DTLVardef@aa6be0_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2022

Variable impact of geochemical gradients on the functional potential of bacteria, archaea, and phages from the permanently stratified Lac Pavin

Permanently stratified lakes contain diverse microbial communities that vary with depth, and so serve as useful models for studying the relationships between microbial community structure and geochemistry. Recent work has shown that these lakes can also harbor numerous bacteria and archaea from novel lineages, including those from the Candidate Phyla Radiation (CPR). However, the extent to which geochemical stratification differentially impacts carbon metabolism and overall genetic potential in CPR bacteria compared to other organisms is not well defined. Here, we determine the distribution of microbial lineages along an oxygen gradient in Lac Pavin, a deep, stratified lake in central France, and examine the influence of this gradient on their metabolism. Genome-based analyses revealed an enrichment of distinct C1 and CO2 fixation pathways in the oxic lake interface and anoxic zone/sediments, suggesting that oxygen likely plays a role in structuring metabolic strategies in non-CPR bacteria and archaea. Notably, we find that oxidation of methane and its byproducts is largely spatially separated from methane production, which is mediated by diverse communities of sediment methanogens that vary on the centimeter scale. In contrast, we detected evidence for RuBisCO throughout the water column and sediments, including form II/III and form III-related enzymes encoded by CPR bacteria in the water column and DPANN archaea in the sediments. Overall, CPR bacteria and phages did not show strong signals of gene content differentiation by depth, despite the fact that distinct species groups populate different lake and sediment compartments. Thus, environmental gradients in Lac Pavin probably select for the capacities of CPR bacteria and phages to a lesser extent than other bacteria and archaea, possibly because selection on the former groups is indirect and depends on host characteristics.

microbiology↗