Biology subjects

Freyria, N. J.

Publications and source records attributed to Freyria, N. J..

4 recordsLinked to original sources

bioRxiv2026

Long-term patterns of ultra-low sulfur fuel oil bioremediation in Arctic shorelines using in situ mesocosms

New maritime regulations restricting high-sulfur fuels have led to the transition to new low sulfur fuel oils (LFSOs). We do not know how LSFOs will behave in marine environments and how they will respond to available remediation strategies, presenting an environmental risk. The risk will be even higher in the remote high Arctic, especially along the Northwest Passage (NWP), for which an increase in shipping traffic is expected by the end of the century. In this study, we evaluated the long-term (one year) biodegradation potential of the native microbial community of NWP beach sediment using in situ mesocosm experiments with two different types of LSFOs: a marine gas oil (Marine diesel) and an ultra-low sulfur fuel oil (ULSFO). We observed that the lighter Marine diesel was biodegraded better (72.0%) than the heavier ULSFO (32.5%). We described composition of the microbial community of the mesocosms using 16S rRNA gene amplicon sequencing and observed a decrease in microbial diversity for the fuel-treated samples compared to the untreated controls. Despite the decrease in overall diversity, we observed significantly higher abundances of known hydrocarbon degrading microbes (e.g., Oleispira, Altererythrobacter, Gilvibacter, Pseudohongiella) in the fuel mesocosms. Our study showed the potential to implement biodegradation as a remediation strategy under the cold and oligotrophic environmental conditions present throughout the NWP. However, we also observed that microbes on their own cannot degrade the entirety of the removed fuel and other types of remediation will need to be considered to complement the natural biodegradation observed here.

microbiology↗

bioRxiv2025

From Northwest Passage shores to molecular pathways: Comparative transcriptomic responses of a novel Arctic marine fuel-degrading Flavobacterium species

Accelerated sea-ice decline is opening the Arctic to increased shipping, elevating the risk of marine fuel spills in fragile ecosystems where extreme cold and remoteness limit cleanup options. While microbial biodegradation is the primary removal mechanism, the metabolic strategies of abundant polar taxa remain poorly understood, particularly those lacking canonical degradation genes. We characterized the hydrocarbon degradation mechanisms of Flavobacterium sp. strain R2B_3I, a psychrotolerant isolate from high Arctic beach sediments in Resolute Bay, Nunavut, Canada. During three-month incubations with ultra-low sulfur fuel oil at 4 {degrees}C, R2B_3I mounted a systems-level response involving the upregulation of diverse non-canonical oxidoreductases, membrane remodeling systems, cold-shock, and oxidative stress defenses. Crucially, this strain achieved efficient degradation in the complete absence of alkB alkane hydroxylases, challenging the reliance on alkB as a universal biomarker for hydrocarbon biodegradation. Transcriptomic analysis revealed distinct temporal shifts, linking specific gene clusters to the degradation of complex petroleum mixtures under environmentally relevant conditions. These results demonstrate that Flavobacterium, a dominant genus in polar oceans, utilize a "cryptic" metabolic network to process hydrocarbons, effectively bypassing the pathways typically monitored in environmental surveys. By uncovering alternative mechanisms, our study revises current models of microbial oil degradation, highlighting the overlooked potential of non-canonical degraders in determining the fate of marine fuel spills in a warming Arctic.

microbiology↗

bioRxiv2025

Transcriptomic analyses unveil hydrocarbon degradation mechanisms in a novel polar Rhodococcus sp. strain R1B_2T from a high Arctic intertidal zone exposed to ultra-low sulfur fuel oil.

As Arctic shipping increases due to climate change, characterized by rising temperature and decreasing sea-ice coverage, the risk of oil spills through the Northwest Passage in this fragile ecosystem grows, necessitating effective bioremediation strategies. Research on bioremediation using Arctic coastal sediment bacteria has gained attention, particularly Rhodococcus species that play key roles in hydrocarbon degradation (HD) under extreme conditions. This study investigates the HD capabilities of a novel cryophilic Arctic Rhodococcus sp. strain R1B_2T isolated from Canadian high Arctic beach sediment in Resolute Bay, exposed to ultra-low sulfur fuel oil for three months at 5 {degrees}C. Comparative transcriptomics analyses revealed dynamic responses and metabolic plasticity, with upregulation of genes for aliphatic, aromatic, and polycyclic aromatic hydrocarbons, biosurfactant production (rhamnolipid), cold adaptation, and stress responses. The strain possesses several key alkane degradation genes (alkB, almA, CYP153, ladA), with co-expression network analysis highlighting synergistic mechanisms between alkB and CYP153 that target different chain-length alkanes (alkB: [~]C5-C20; CYP153: [~]C5-C12 and >C30) demonstrating complementary degradation strategies. The findings reveal adaptive mechanisms and degradation kinetics of native Arctic bacteria, highlighting the potential of Arctic cryophilic and halotolerant Rhodococcus species for oil spill remediation in polar marine environments. HIGHLIGHTS- Novel cryophilic Arctic Rhodococcus strain R1B_2T demonstrates robust hydrocarbon degradation capabilities at 4{degrees}C - Transcriptomic analysis reveals upregulation of key genes for aliphatic, aromatic, and PAH degradation pathways - Synergistic expression between alkB, almA and CYP153 genes enables efficient degradation of varied hydrocarbon chain lengths - Concurrent upregulation of biosurfactant production linked to hydrocarbon biodegradation, cold adaptation, and stress response mechanisms GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=146 SRC="FIGDIR/small/664532v1_ufig1.gif" ALT="Figure 1"> View larger version (65K): org.highwire.dtl.DTLVardef@16fa663org.highwire.dtl.DTLVardef@114e2a2org.highwire.dtl.DTLVardef@2b244borg.highwire.dtl.DTLVardef@5bb803_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2021

Within-Arctic horizontal gene transfer as a driver of convergent evolution in distantly related microalgae

The Arctic Ocean is being impacted by warming temperatures, increasing freshwater and highly variable ice conditions. The microalgal communities underpinning Arctic marine food webs, once thought to be dominated by diatoms, include a phylogenetically diverse range of small algal species, whose biology remains poorly understood. Here, we present genome sequences of a cryptomonad, a haptophyte, a chrysophyte, and a pelagophyte, isolated from the Arctic water column and ice. Comparing protein family distributions and sequence similarity across a densely-sampled set of algal genomes and transcriptomes, we note striking convergences in the biology of distantly related small Arctic algae, compared to non-Arctic relatives; although this convergence is largely exclusive of Arctic diatoms. Using high-throughput phylogenetic approaches, incorporating environmental sequence data from Tara Oceans, we demonstrate that this convergence was partly explained by horizontal gene transfers (HGT) between Arctic species, in over at least 30 other discrete gene families, and most notably in ice-binding domains (IBD). These Arctic-specific genes have been repeatedly transferred between Arctic algae, and are independent of equivalent HGTs in the Antarctic Southern Ocean. Our data provide insights into the specialized Arctic marine microbiome, and underlines the role of geographically-limited HGT as a driver of environmental adaptation in eukaryotic algae.

evolutionary biology↗