Biology subjects

Izabel-Shen, D.

Publications and source records attributed to Izabel-Shen, D..

4 recordsLinked to original sources

bioRxiv2026

Benchmarking the quantitative performance of metabarcoding and shotgun sequencing using mock communities of marine nematodes

High-throughput sequencing has transformed biodiversity assessment and ecological monitoring, yet its quantitative reliability remains unclear. Here, we assembled two experiments of nematode mock communities: one based on extracted DNA and one on individual specimens. Although DNA extraction was required in both experiments to assess the quantitative performance of the sequencing approaches, we essentially evaluated whether this performance was influenced by differences in the start material used to constructed the mock communities. Each community was analyzed using 18S and 28S metabarcoding and shotgun sequencing to evaluate their ability to resolve quantitative information. Across datasets, the number of observed taxa increased with sequencing depth despite controlled input, indicating that higher read numbers primarily revealed intragenomic variation in nematodes than true diversity. Community composition was more accurately recovered by 18S metabarcoding and shotgun sequencing than by 28S. Both sequencing approaches reflected DNA input reasonably well; however, shotgun sequencing provided more consistent abundance estimates relative to individual counts, particularly for nematodes with relatively large-bodied size. In contrast, all methods showed limited ability to accurately quantify taxa with low DNA input or small body size. Comparisons between mock community types showed strong correspondence between read abundance and DNA input, but weaker relationships with individual counts. Overall, both metabarcoding and shotgun sequencing effectively detected community-level patterns and within-taxon abundance, but shotgun sequencing was more reliable for cross-taxon quantitative comparisons. Our findings demonstrate how input material, primer choice, and sequencing approach influence the accuracy of nematode abundance estimates, and provide guidance for improving quantitative applications in nematode-based bioindication and, more broadly environmental DNA biomonitoring.

ecology↗

bioRxiv2022

Genome size variation between pelagic and benthic communities across prokaryotic taxonomy and environmental gradients in the Baltic Sea

While theories and models have appeared to explain genome size as a result of evolutionary processes, little work has shown that genome sizes carry ecological signatures. Our work delves into the ecological implications of microbial genome size variation in benthic and pelagic habitats across environmental gradients of the brackish Baltic Sea. While depth is significantly associated with genome size in benthic and pelagic brackish metagenomes, salinity is only correlated to genome size in benthic metagenomes. Overall, we confirm that prokaryotic genome sizes in Baltic sediments (3.47 Mbp) are significantly bigger than in the water column (2.96 Mbp). While benthic genomes have a higher number of functions than pelagic genomes, the smallest genomes coded for a higher number of module steps per Mbp for most of the functions irrespective of their environment. Some examples of this functions are amino acid metabolism and central carbohydrate metabolism. However, we observed that nitrogen metabolism was almost absent in pelagic genomes and was mostly present in benthic genomes. Finally, we also show that Bacteria inhabiting Baltic sediments and water column not only differ in taxonomy, but also in their metabolic potential, such as the Wood-Ljungdahl pathway or the presence of different hydrogenases. Our work shows how microbial genome size is linked to abiotic factors in the environment, metabolic potential and taxonomic identity of Bacteria and Archaea within aquatic ecosystems.

microbiology↗

bioRxiv2021

Recurrent micropollutant exposure leads to divergent degradation abilities and community succession in a freshwater microbiome

The increasing-volume release of micropollutants into natural surface waters has raised great concern due to their environmental accumulation. Persisting micropollutants can impact multiple generations of organisms, but their microbially-mediated degradation and their influence on community assembly remain understudied. Here, freshwater microbes were treated with several common micropollutants, alone or in combination, and then transferred every 5 days to fresh medium containing the same micropollutants to mimic the repeated exposure of microbes. Metabarcoding of 16S rRNA gene makers was chosen to study the succession of bacterial assemblages following micropollutant exposure. The removal rates of micropollutants were then measured to assess degradation capacity of the associated communities. The degradation of micropollutants did not accelerate over time but altered the microbial community composition. Community assembly was dominated by stochastic processes during early exposure, via random community changes and emergence of seedbanks, and deterministic processes later in the exposure, via advanced community succession. Early exposure stages were characterized by the presence of sensitive microorganisms such as Actinobacteria and Planctomycetes, which were then replaced by more tolerant bacteria such as Bacteroidetes and Gammaproteobacteria. Our findings have important implication for ecological feedback between microbe-micropollutants under anthropogenic climate change scenarios.

ecology↗

bioRxiv2021

Abundance-occupancy relationships along taxonomic ranks reveal a consistency of niche differentiation in marine bacterioplankton with distinct lifestyles

Abundance-occupancy relationships (AORs) are an important determinant of biotic community dynamics and habitat suitability. However, little is known about their role in complex bacterial communities, either within a phylogenetic framework or as a function of niche breadth. Based on data obtained in a field study in the St. Lawrence Estuary, we used 16S rRNA gene sequencing to examine the vertical patterns, strength, and character of AORs for particle-attached and free-living bacterial assemblages. Free-living communities were phylogenetically more diverse than particle-attached communities. The dominant taxa were consistent in terms of their presence/absence but population abundances differed in surface water vs. the cold intermediate layer. Significant, positive AORs characterized all of the surveyed communities across all taxonomic ranks of bacteria, thus demonstrating an ecologically conserved trend for both free-living and particle-attached bacteria. The strength of the AORs was low at the species level but higher at the genus and phylum levels. These results demonstrate that an assessment of the distributions and population densities of finely resolved taxa does not necessarily improve determinations of apparent niche differences in marine bacterioplankton communities at regional scales compared with the information inferred from a broad taxonomic classification. Subject Categorymicrobial population and community ecology

ecology↗