Darya Slonova

The St. Anna Trough region is a key Eurasian Arctic gateway connecting the northeastern Barents Sea, northern Kara Sea, and central Arctic Ocean. The region is characterized by complex hydrodynamics, with multiple water masses of local and Atlantic origin interacting and undergoing transformation. In this study, we investigated whether seawater microbiome composition correlates with water-mass origin and can be used to help delineate water masses. We collected 115 seawater samples representing major regional water masses - Arctic surface water, meltwater, cold dense water, Barents Sea branch water, the recently discovered Keldysh Current water, and mixed waters - and analyzed them using 16S rRNA gene amplicon sequencing. We found that microbiome composition closely followed water mass structure, which, together with thermohaline properties and depth, explained the majority (61.2%) of microbiome composition variation. Distinct microbial patterns were associated with Atlantic and Arctic water masses, except for the Arctic surface water, which lacked a distinct microbiome and resembled those of meltwater or the Keldysh Current microbiomes. Differential abundance and network analyses revealed characteristic bacterial markers: SAR11 (Clades Ia and IV), Roseibacillus , SV1-3 ( Microbacteriaceae ), SAR86 clade, and AEGEAN-169 marine group in the Keldysh Current; Halieaceae , Planktomarina , NS5 marine group, and Sulfitobacter in meltwater; SUP05 cluster, SAR86, SAR92, and SAR324 clade in cold dense water; Nitrincolaceae and Amylibacter in Barents Sea branch water; Flavobacteriaceae and Chitinophagales in mixed waters. These differences were driven primarily by shifts in relative abundance of widespread Arctic bacterial taxa rather than by differential prevalence of bacterial groups. Our results demonstrate that seawater microbiomes can serve as sensitive biological tracers of water mass origin and transformation in the Eurasian Arctic. Furthermore, the distinct Keldysh Current microbiome supports its recognition as a novel hydrographic feature and indicates its role as a biological corridor transporting Atlantic-associated biota eastward toward the Kara Sea. These findings suggest that “Atlantification” of Eurasian Arctic includes a microbial component, highlighting marine microbiomes as indicators of ongoing ecological changes in the Arctic Ocean.

Objectives: The study aimed to evaluate the antibacterial and wound-healing potential of the engineered lysin GRC-ML07 in a mouse model of full-thickness wounds infected with multidrug-resistant Pseudomonas aeruginosa under immunosuppression. Methods: Male BALB/c mice (22–24 g) were immunocompromised with cyclophosphamide. Three days later, full-thickness excisional wounds were created and infected with P. aeruginosa (10⁷ cells/wound). The lysin GRC-ML07 incapsulated into an alginate gel was applied topically to the wound area twice a day for four days after infection. Wound swabs for microbiological assays and scab tissues for cytokine and cellular profiling were collected on days 4 and 7. Histological samples were taken on days 4, 7, 14, and 21. Results: Lysin GRC-ML07 induced bacterial lysis accompanied by low activation of TLR2, TLR4, or TLR7/8 signaling pathways and pro-inflammatory cytokine production in vitro. Its application in vivo resulted in decreased levels of GM-CSF, IL-1β, IL-6, IL-17A, and TNF-α in the wound, accompanied by a 46% increase in neutrophil counts on day 4 compared to control and placebo (alginate gel) groups. By day 7, lysin treatment reduced bacterial load by 2 log, decreased neutrophil counts in wounds, and led a transition of the wounds to the granulation and epithelialization phase with scab desquamation. Conclusions: It was first shown that engineered lysin GRC-ML07 exhibits not only antibacterial, but pronounced pro-healing effects in immunocompromised mice, promoting resolution of inflammation and transition to the granulation/epithelialization phase.

Extraction of high-quality microbial DNA remains a critical bottleneck in metagenomic research. Environmental samples often produce fragmented DNA and are prone to contaminations that interfere with downstream sequencing, while widely used commercial kits can be prohibitively expensive. Therefore, systematic evaluation of cost-effective alternatives is essential to support large-scale metagenomic studies. In this work, we benchmarked eight commercial DNA extraction kits from Magen, SkyGen, and Sileks against Qiagen reference kits. Four representative sample types were analyzed: freshwater, seafloor sediments, Pacific oyster (Magallana gigas) gut microbiome, and mammalian feces. DNA yield, integrity, purity, PCR inhibitor content, and eukaryotic DNA admixture were assessed. Microbial community composition, alpha diversity, reproducibility, and contamination (“kitome” and “splashome”) were further evaluated using 16S rRNA amplicon sequencing. We revealed that several alternative kits performed comparably or better than the Qiagen reference standard. Magen Soil and Magen Bacterial provided high yields and reproducibility, though the latter produced more fragmented DNA. SkyGen Stool excelled with host-associated samples, while Sileks Soil and Metagenomic kits preserved higher diversity in sediments. Magen Microbiome consistently underperformed. This study identifies multiple cost-effective DNA extraction strategies and provides practical guidance for selecting balanced DNA purification methods for different sample types.

PGLYRP1/Tag-7/PGRP-S is one of mammalian peptidoglycan recognition proteins (PGRPs). Here, we demonstrate that human recombinant PGLYRP1/Tag-7/PGRP-S potentiates the response of murine macrophage-like ANA-1 cells and human macrophages to facultative intracellular pathogen Listeria monocytogenes. PGLYRP1/Tag-7/PGRP-S binds to the surface of L. monocytogenes and other bacterial cells but has no effect on their growth in culture. While PGLYRP1/Tag-7/PGRP-S treatment modestly enhanced phagocytosis of bacteria by ANA-1 cells, the intracellular survival of PGLYRP1/Tag-7/PGRP-S treated L. monocytogenes was strongly inhibited 2 h after internalization. PGLYRP1/Tag-7/PGRP-S treatment of bacteria boosted oxidative burst induction and increased the level of proinflammatory cytokine IL-6 produced by ANA-1, however, these effects happened too late to be responsible for decreased intracellular survival of bacteria. Our results thus suggest that PGLYRP1/Tag-7/PGRP-S acts as a molecular sensor for detection of L. monocytogenes infection of mammalian cells that leads to increased killing through a mechanism(s) that remains to be defined.