Biology subjects

Durieu, B.

Publications and source records attributed to Durieu, B..

7 recordsLinked to original sources

bioRxiv2026

An endolithic Gloeobacter and other novel cyanobacterial diversity in alpine dolomites of Piora Valley

Background: Cyanobacteria are the major phototrophs in many endolithic ecosystems, yet their genomic diversity and metabolic adaptations remain poorly characterized. Here, we investigated cyanobacterial diversity in endolithic dolomite rocks from the Piora Valley in the southern Swiss Alps using genome-resolved metagenomics. Results: We reconstructed 138 medium-quality metagenome-assembled genomes (MAGs) from four neighboring endolithic rock communities, including 15 cyanobacterial MAGs distributed across six order-level lineages. The cyanobacterial communities showed limited taxonomic overlap among rocks, and most recovered MAGs represented potentially novel species. Only one Gloeobacter lineage occurred in all sampled rocks, which we propose as Gloeobacter dolomitensis sp. nov., representing the first Gloeobacter genome recovered from an endolithic environment. Comparative genomic analyses identified a cynS gene encoding cyanase unique to G. dolomitensis among the Gloeobacter. Phylogenetic analyses support its horizontal acquisition from Pseudomonadota. Interestingly, the genome of G. dolomitensis lacks a canonical CynABD cyanate transporter and instead contains a distinct ATP-synthase binding cassette (ABC) transporter adjacent to cynS. Although the available genomic and structural evidence does not establish cyanate transport, its genomic association with cynS suggests a potentially non-canonical mechanism. We further show that horizontal gene transfer was unevenly distributed among cyanobacterial lineages, with Acaryochloridales acting predominantly as donors, Chroococcidiopsidales as recipients, and Gloeobacterales showing a comparatively high frequency of interphylum gene exchange. Conclusions: The Piora Valley dolomite environment represents an underexplored reservoir of cyanobacterial diversity, including basal and previously undescribed lineages. The discovery of G. dolomitensis and its unusual cyanate-associated genomic architecture expands our understanding of Gloeobacterales diversity and highlights the potential importance of horizontal gene acquisition and metabolic innovation in endolithic microbial communities.

evolutionary biology↗

bioRxiv2026

Taxonomic Description of Uncultured Cyanobacteria from Extreme Habitats through Genome-Based Classification

Cyanobacteria form a morphologically and phylogenetically diverse group of oxygenic phototrophic bacteria inhabiting a wide range of environments, including extreme habitats such as hot springs and volcanic steam vents. Many lineages, particularly those from these extreme environments, remain uncultured and are known only from metagenome-assembled genomes (MAGs), limiting their integration into formal taxonomy. Analysis of 46 steam vent associated samples from Hawai i using 16S rRNA amplicon sequencing revealed that cyanobacteria dominate these communities. Gloeobacter kilaueensis dominated pit-like environments with low-light conditions, while Leptolyngbyaceae and other families are more dominant in structured soil and wall communities. We further reconstructed 38 high-quality cyanobacterial MAGs and incorporated them into a phylogenomic analysis comprising 343 cyanobacterial genomes, followed by genome-based comparisons against 9,026 reference genomes. This revealed eight novel species and one novel genus spanning five orders: Chroococcidiopsidales, Leptolyngbyales, Nostocales, Oculatellales, and Oscillatoriales. Following SeqCode guidelines, we provide the first formal taxonomic descriptions of cyanobacterial MAGs and propose guidelines for integrating genome-based and cultivated material. These findings highlight Hawaiian steam vents as hotspots of previously uncharacterized cyanobacterial diversity and underscore the importance of genome-based nomenclature.

genomics↗

bioRxiv2025

A FAIR Amplicon Sequencing Workflow for Long-term Environmental Monitoring

Antarctica represents one of the last pristine environments on Earth, providing a unique opportunity to to study the effects of climate change and anthropogenic activities. Ice-free areas, such as the inland nunataks of the Sor Rondane Mountains (SRM), host unique terrestrial and lacustrine ecosystems, of which the simplified food webs rely almost exclusively on microbial primary production. Because of their small size, low productivity and hence low biomass, these microbial communities are fragile. Seven SRM sites were selected to be part of the Antarctic Specially Protected Area (ASPA) 179. The MonASPA project has established an environmental monitoring program to evaluate the effectiveness of the management plan approved by the Antarctic Treaty System for these areas. A key component of MonASPA is the long-term monitoring of microbial biodiversity using 16S rRNA amplicon sequencing. To ensure consistent operation over decades, we developed the Reproducible Amplicon Sequencing Pipeline for Antarctic Monitoring (RASPAM), which is built on Apptainer containers and Nextflow workflows. RASPAM implements Amplicon Sequence Variants (ASVs) and Zero-radius Operational Taxonomic Units (ZOTUs) to provide high-resolution taxonomic affiliation. It incorporates, in addition to the SILVA database, a taxonomically curated 16S rRNA database for cyanobacteria and enables comparisons against NCBI databases to facilitate the identification of rare prokaryotic strains in environmental samples. RASPAM is Findable, Accessible, Interoperable, and Reproducible (FAIR) and represents a robust tool for long-term monitoring of microbial communities in Antarctic and other extreme environments.

bioinformatics↗

bioRxiv2023

Ecophysiological and genomic approaches to cyanobacterial hardening for soil restoration

Cyanobacteria inhabit extreme environments, including drylands, providing multiple benefits to the ecosystem. Soil degradation in warm drylands is increasing due to land-use intensification. Restoration methods adapted to the strong stress in drylands are being developed, i.e. cyanobacterial inoculation to recover biocrusts. For success, it is crucial to optimize the survival of inoculated cyanobacterial in field. One strategy is to harden them to be re-adapted to stressful conditions after laboratory culturing. Here, we analyzed the genome and ecophysiological response to osmotic, desiccation and UVR stresses of an Antarctic cyanobacterium, Stenomitos frigidus ULC029, closely related to other cyanobacteria from warm and cold dryland soils. Chlorophyll a concentrations show that preculturing ULC029 under moderate osmotic stress improved its survival during an assay of desiccation plus rehydration under UVR. Besides, its sequential exposition to these stress factors increased the production of exopolysaccharides, carotenoids and scytonemin. Desiccation, but not osmotic stress, increased the concentrations of the osmoprotectants, trehalose and sucrose. However, osmotic stress might induce the production of other osmoprotectants, for which the complete pathways were found in the ULC029 genome. In total, 140 genes known to be involved in stress resistance were annotated and could potentially help ULC029 under stress. Here, we confirm that the sequential application of moderate osmotic stress and dehydration, could improve cyanobacterial hardening for soil restoration, by inducing several resistance mechanisms. We provide a high-quality genome of ULC029 and a description of the main resistance mechanisms found (i.e. production of exopolysaccharides, osmoprotectants, chlorophyll and carotenoids; DNA repair; oxidative stress protection).

microbiology↗

bioRxiv2023

Novel diversity of polar Cyanobacteria revealed by genome-resolved metagenomics

Benthic microbial mats dominated by Cyanobacteria are important features of polar lakes. Although culture-independent studies have provided important insights into their diversity, only a handful of genomes of polar Cyanobacteria have been sequenced to date. Here, we applied a genome-resolved metagenomics approach to data obtained from Arctic, sub-Antarctic, and Antarctic microbial mats. We recovered 22 unique metagenome-assembled genomes (MAGs) of Cyanobacteria, most of which are only distantly related to genomes that have been sequenced so far. These include i) lineages that are common in polar microbial mats such as the filamentous taxa Pseudanabaena, Leptolyngbya, Microcoleus/Tychonema, and Phormidium; ii) the less common taxa Crinalium and Chamaesiphon; iii) an enigmatic Chroococcales lineage only distantly related to Microcystis; and iv) an early branching lineage in the order Gloeobacterales that is almost exclusively restricted to the cold biosphere, for which we propose the name Candidatus Sivonenia alaskensis. Our results show that genome-resolved metagenomics is a powerful tool for expanding our understanding of the diversity of Cyanobacteria, especially in understudied remote and extreme environments. Data summaryThe sequencing data generated in this study have been submitted to the European Nucleotide Archive (ENA) under the BioProject PRJEB59431. Individual accession numbers for raw reads and genomic bins are listed in Table S1 and Table S3, respectively. Genomic bins can also be downloaded from doi.org/10.6084/m9.figshare.22003967. The commands used throughout this study are available in github.com/igorspp/polar-cyanobacteria-MAGs. Impact statementCyanobacteria are photosynthetic microorganisms that play important roles in polar lacustrine ecosystems. Many Cyanobacteria are difficult to grow in the laboratory, particularly in isolation from other organisms, which makes it challenging to sequence their genomes. As such, considerably fewer genomes of Cyanobacteria have been sequenced so far compared to other bacteria. In this study, we used a metagenomics approach to recover novel genomes of Cyanobacteria from Arctic and Antarctic microbial mats without the need to isolate the organisms. The community DNA was extracted and sequenced, and the genomes of individual populations were separated using bioinformatics tools. We recovered 22 different genomes of Cyanobacteria, many of which have not been sequenced before. We describe in more detail an interesting lineage of ancestral Cyanobacteria in the order Gloeobacterales, for which we propose the name Candidatus Sivonenia alaskensis. Our study shows that genome-resolved metagenomics is a valuable approach for obtaining novel genomes of Cyanobacteria, which are needed to improve our understanding of life in the polar regions and the planet at large.

microbiology↗

bioRxiv2022

The GEN-ERA toolbox: unified and reproducible workflows for research in microbial genomics .

BackgroundMicrobial culture collections play a key role in taxonomy by studying the diversity of their accessions and providing well characterized strains to the scientific community for fundamental and applied research. These microbial resource centers thus need to implement new standards in species delineation, including whole-genome sequencing and phylogenomics. In this context, the genomic needs of the Belgian Coordinated Collections of Microorganisms (BCCM) were studied, resulting in the GEN-ERA toolbox. The latter is a unified cluster of bioinformatic workflows dedicated to both bacteria and small eukaryotes (i.e. yeasts). FindingsThis public toolbox allows researchers without a specific training in bioinformatics to perform robust phylogenetic analyses. Hence, it facilitates all steps from genome downloading and quality assessment, including genomic contamination estimation, to tree reconstruction. It also offers workflows for average nucleotide identity comparisons and metabolic modeling. Technical detailsNextflow workflows are launched by a single command and are available on the GEN-ERA GitHub repository (https://github.com/Lcornet/GENERA). All the workflows are based on Singularity containers to increase reproducibility. TestingThe toolbox was developed for a diversity of microorganisms, including bacteria and fungi. It was further tested on an empirical dataset of 18 (meta)genomes of early-branching Cyanobacteria, providing the most up-to-date phylogenomic analysis of the Gloeobacterales order, the first group to diverge in the evolutionary tree of Cyanobacteria. ConclusionThe GEN-ERA toolbox can be used to infer completely reproducible comparative genomic and metabolic analyses on prokaryotes and small eukaryotes. Although designed for routine bioinformatics of culture collections, it can also be useful for other applications, as shown by our case study on Gloeobacterales.

bioinformatics↗

bioRxiv2018

Consensus assessment of the contamination level of publicly available cyanobacterial genomes

BACKGROUNDPublicly available genomes are crucial for phylogenetic and metagenomic studies, in which contaminating sequences can be the cause of major problems. This issue is expected to be especially important for Cyanobacteria because axenic strains are notoriously difficult to obtain and keep in culture. Yet, despite their great scientific interest, no data are currently available concerning the quality of publicly available cyanobacterial genomes.\n\nRESULTSAs reliably detecting contaminants is a complex task, we designed a pipeline combining six methods in a consensus strategy to assess the contamination level of 440 genome assemblies of Cyanobacteria. Two methods are based on published reference databases of ribosomal genes (SSU rRNA 16S and ribosomal proteins), one is indirectly based on a reference database of marker genes (CheckM), and three are based on complete genome analysis. Among those genome-wide methods, Kraken and DIAMOND blastx share the same reference database that we derived from Ensembl Bacteria, whereas CONCOCT does not require any reference database, instead relying on differences in DNA tetramer frequencies. Given that all the six methods appear to have their own strengths and limitations, we used the consensus of their rankings to infer that >5% of cyanobacterial genome assemblies are highly contaminated by foreign DNA (i.e., contaminants were detected by 5 or 6 methods).\n\nCONCLUSIONSOur results will help researchers to check the quality of publicly available genomic data before use in their own analyses. Moreover, we argue that journals should make mandatory the submission of raw read data along with genome assemblies in order to facilitate the detection of contaminants in sequence databases.

genomics↗