Biology subjects

Jardillier, L.

Publications and source records attributed to Jardillier, L..

7 recordsLinked to original sources

bioRxiv2026

Comparing DNA Extraction Protocols for Freshwater Prokaryotic Communities: Impacts on Yield and Microbial Profiling

DNA extraction from aquatic samples is a critical process that influences the quantity and purity of the DNA obtained. This can have profound effects on the accuracy of the community depiction. In this study, DNA extraction workflows of seven commercial kits (Qiagen: DNeasy PowerLyzer PowerSoil, DNeasy PowerSoil Pro, DNeasy PowerSoil, DNeasy PowerMax Soil; Macherey-Nagel: NucleoSpin Soil; Zymo: ZymoBIOMICS DNA; MP Biomedicals: FastDNA SPIN), along with several modifications of manufacturer's protocols focusing on the lysis and elution steps, were tested, accounting for a total of 18 different protocols. For each protocol, DNA yield (quantity, replicability and quality), richness and compositional reproducibility based on 16S rRNA gene sequencing, as well as processing time and cost were assessed. The standard protocols recommended by the manufacturer showed comparable DNA yield results. Shared ASVs between all protocols accounted for >90% of the reads and were mostly abundant ASVs, indicating consistent detection of dominant taxa across all protocols. Adding supplementary lysis and elution steps to the manufacturer's protocols yielded up to ~4x more DNA. However, total read counts and ASV richness were lower as total DNA increased. Manufacturer's protocols therefore showed higher values than their modified versions, although these effects were not significant on community composition. We conclude that the choice of a protocol is the balance between recovering sufficient DNA of good quality versus potential effects on downstream sequencing output (reads and ASVs).

microbiology↗

bioRxiv2025

Higher trophic status leads to more diverse and divergent microeukaryote communities over time in urban lakes from the Greater Paris (France)

Effects of trophic status on lake microeukaryote community dynamics remain underexplored. Spanning oligotrophic to hypereutrophic conditions, peri-urban lakes located in the Greater Paris region (France) offer unique opportunities to compare these dynamics along a eutrophication gradient. Here, community composition was characterized using 18S rRNA gene metabarcoding, and analyzed in the context of environmental parameters and chlorophyll a-derived trophic status throughout an 18-month sampling period. Microeukaryote assemblages were dominated by Cryptophyceae, Spirotrichea, Chrysophyceae, and Chlorophyceae, with mixotrophic and heterotrophic taxa dominating across all lakes. Taxa richness peaked at intermediate trophic levels, consistent with the intermediate disturbance hypothesis. Beta-diversity and network analyses revealed increasing community modularity, reduced connectivity, and enhanced temporal variability with higher trophic status. In lakes reaching the hypereutrophic status, communities diverged progressively over time, suggesting the onset of regime shifts. Conversely, oligo-to mesotrophic lakes maintained more connected and stable assemblages. These findings demonstrate that eutrophication fosters more diverse and increasingly divergent microeukaryote communities, underscoring its role as a central driver of microbial community restructuring in urban freshwater systems.

microbiology↗

bioRxiv2024

A summer in the Greater Paris: trophic status of peri-urban lakes shapes prokaryotic community structure and functional potential

With more than 12 million inhabitants, the Greater Paris offers a "natural laboratory" to explore the effects of eutrophication on freshwater lakes within a relatively restricted area. Here, a four-month time-series was carried out during summertime to monitor planktonic microbial communities of nine lakes located within a [~]70 km radius around Paris (Ile-de-France, France) of comparable morphologies, yet distinct trophic statuses (mesotrophic to hypereutrophic). The contribution of the trophic status and intra-summer variations were investigated on prokaryotic community structures (16S rRNA gene sequencing) and functions (shotgun metagenomics). Sampled lakes harbored highly distinct and diverse prokaryotic communities. Although their gene pool was quite stable and shared among lakes, taxonomical and functional changes were correlated. The trophic status appears as the main driver of both community structure and functional potential. When focusing on function involved in biogeochemical cycles, responses to phosphorus limitation (mostly polyphosphate-related processes) were highlighted between trophic statuses. Hypereutrophic lakes communities displayed the highest contrast and heterogeneity over time, suggesting a regime shift compared to lakes of lower trophic status. This study explores the influence of eutrophication on lakes microbiome ecology, by comparing for the first time the planktonic microbial communities and their functional potential of lakes of distinct trophic status in close vicinity over a summer season.

microbiology↗

bioRxiv2024

Culture- and genome-based characterization of a tripartite interaction between patescibacterial epibionts, methylotrophic proteobacteria, and a jumbo phage in freshwater ecosystems

Patescibacteria form a very diverse and widely distributed phylum of small bacteria inferred to have an episymbiotic lifestyle. However, the prevalence of this lifestyle within the phylum and their host specificity remain poorly known due to the scarcity of cultured representatives. Here, we describe a complex system consisting of a patescibacterium, its gammaproteobacterial hosts, and their respective phages based on enrichment cultures and metagenomic data from two shallow, geographically close, freshwater ecosystems. The patescibacterium, Strigamonas methylophilicida sp. nov., defines a new genus within the family Absconditicoccaceae. It grows as epibiont on cells of methanotrophic species of the gammaproteobacterial family Methylophilaceae. Strigamonas cells grow tightly attached to the host, sometimes forming stacks that connect two host cells. Despite a surprisingly large genome (1.9 Mb) compared to many other Patescibacteria, S. methylophilicida lacks many essential biosynthetic pathways, including the complete biosynthesis of phospholipids, amino acids, and nucleic acids, implying a dependence on the host to obtain these molecules. We also identified and assembled the complete genomes of one patescibacterial phage that might represent a new virus family within the class Caudoviricetes, and two Methylophilaceae phages predicted to have head-tailed and filamentous virions, respectively. The patesciphage uses a modified genetic code similar to that of its host and encodes four tRNA genes, including the suppressor tRNA gene for the UGA stop codon, which is reassigned to glycine in many Patescibacteria. Our results confirm a prevalent episymbiotic lifestyle in Absconditicoccaceae and further suggest a clade-specific adaptation of this patescibacterial family for gammaproteobacterial hosts. IMPORTANCEPatescibacteria are ultra-small bacteria with reduced genomes that rely on symbiotic interactions with other prokaryotes, yet their host specificity and associated viral parasites remain poorly characterized due to limited cultured representatives. Here, we describe Strigamonas methylophilicida, a new patescibacterial species of the family Absconditicoccaceae that grows as an epibiont on various methylotrophic Gammaproteobacteria. This expands the host range for this family beyond previously documented photosynthetic partners. Using enrichment cultures and metagenomics, we retrieved complete genomes of novel phages infecting S. methylophilicida and its hosts, including one phage that uses a modified genetic code matching that of the patescibacterium. These findings reveal a previously unrecognized patescibacteria- methylotroph-phage tripartite interaction in freshwater environments, highlight the adaptations of patescibacterial phages, and shed light on the complex ecology and evolution of host-parasite-phage dynamics in understudied bacterial lineages.

microbiology↗

bioRxiv2021

Viral and parasitic cell ratios per free-living microbe across ecosystems

It is generally assumed that viruses outnumber cells on Earth by at least tenfold. Virus-to-microbe ratios (VMR) are largely based on counts of fluorescently labelled virus-like particles. However, these exclude intracellular viruses and potentially include false positives (DNA-containing vesicles, gene-transfer agents, unspecifically stained inert particles). Here, we develop a metagenome-based VMR estimate (mVRM) that accounts for DNA viruses across all stages of their replication cycles (virion, intracellular lytic and lysogenic) by using normalised RPKM (reads per kilobase of gene sequence per million of mapped metagenome reads) counts of the major capsid protein (MCP) genes and cellular universal single-copy genes (USCGs) as proxies for virus and cell counts, respectively. After benchmarking this strategy using mock metagenomes with increasing VMR, we inferred mVMR across different biomes. To properly estimate mVMR in aquatic ecosystems, we generated metagenomes from co-occurring cellular and viral fractions (>50 kDa-200 {micro}m size-range) in freshwater, seawater and solar saltern ponds (10 metagenomes, 2 control metaviromes). Viruses outnumbered cells in freshwater by [~]13 fold and in plankton from marine and saline waters by [~]2-4 fold. However, across an additional set of 121 diverse non-aquatic metagenomes including microbial mats, microbialites, soils, freshwater and marine sediments and metazoan-associated microbiomes, viruses, on average, outnumbered cells by barely two-fold. Although viruses likely are the most diverse biological entities on Earth, their global numbers might be closer to those of cells than previously estimated.

microbiology↗

bioRxiv2020

Environmental drivers of plankton protist communities along latitudinal and vertical gradients in the oldest and deepest freshwater lake

Identifying which abiotic and biotic factors determine microbial community assembly is crucial to understand ecological processes and predict how communities will respond to environmental change. While global surveys aim at addressing this question in the worlds oceans, equivalent studies in large freshwater systems are virtually lacking. Being the oldest, deepest and most voluminous freshwater lake on Earth, Lake Baikal offers a unique opportunity to test the effect of horizontal versus vertical gradients in community structure. Here, we characterized the structure of planktonic microbial eukaryotic communities (0.2-30 {micro}m cell size) along a North-South latitudinal gradient ([~]600 km) from samples collected in coastal and pelagic waters and from surface to the deepest zones (5-1400 m) using an 18S rRNA gene metabarcoding approach. Our results show complex and diverse protist communities dominated by alveolates (ciliates and dinoflagellates), ochrophytes and holomycotan lineages, with cryptophytes, haptophytes, katablepharids and telonemids in moderate abundance and many low-frequency lineages, including several typical marine members, such as diplonemids, syndinians and radiolarians. Depth had a strong significant effect on protist community stratification. By contrast, the effect of the latitudinal gradient was marginal and no significant difference was observed between coastal and surface open water communities. Co-occurrence network analyses showed that epipelagic communities are much more interconnected than meso- and bathypelagic communities and suggest specific biotic interactions between autotrophic, heterotrophic and parasitic lineages that influence protist community structure. Since climate change is rapidly affecting Siberia and Lake Baikal, our comprehensive protist survey constitutes a useful reference to monitor ongoing community shifts. Originality and Significance StatementLake Baikal is the oldest, deepest and most voluminous freshwater lake on Earth, offering a unique opportunity to test the effects of horizontal versus vertical gradients on microbial community structure. Using a metabarcoding approach, we studied planktonic microbial eukaryotes from Baikal water columns (5 up to 1,400 m depth) across a North-South latitudinal gradient ([~]600 km), including coastal and pelagic areas. Our results show that depth has a strong effect on protist community assemblage, but not latitude (minor effect) or coastal vs. open water sites (no effect). Co-occurrence analyses also point to specific biotic interactions as drivers of community structure. This comprehensive survey constitutes a useful reference for monitoring active climate change effects in this ancient lake.

microbiology↗

bioRxiv2019

Hyperdiverse archaea near life limits at the polyextreme geothermal Dallol area

Microbial life has adapted to various individual extreme conditions; yet, organisms simultaneously adapted to very low pH, high salt and high temperature are unknown. We combined environmental 16S/18S rRNA-gene metabarcoding, cultural approaches, fluorescence-activated cell sorting, scanning electron microscopy and chemical analyses to study samples along such unique polyextreme gradients in the Dallol-Danakil area (Ethiopia). We identify two physicochemical barriers to life in the presence of surface liquid water defined by: i) high chaotropicity-low water activity in Mg2+/Ca2+-dominated brines and ii) hyperacidity-salt combinations (pH~0/ NaCl-dominated salt-saturation) When detected, life was dominated by highly diverse ultrasmall archaea widely distributed across phyla with and without previously known halophilic members. We hypothesize that high cytoplasmic K+-level was an original archaeal adaptation to hyperthermophily, subsequently exapted during multiple transitions to extreme halophily. We detect active silica encrustment/fossilization of cells but also abiotic biomorphs of varied chemistry. Our work helps circumscribing habitability and calls for cautionary interpretations of morphological biosignatures on Earth and beyond.

microbiology↗