The Gram-negative genus Aeromonas contains diverse bacterial species that are prevalent in aquatic environments. This present study describes three novel Aeromonas strains: A. ichthyocola sp. nov. A-5^T and A. mytilicola subsp. aquatica subsp. nov. A-8^T isolated from rainbow trout (Oncorhynchus mykiss), and A. mytilicola sp. nov. A-7^T isolated from mussels (Mytilus galloprovincialis), respectively. Genomic analyses revealed that strains A-5^T and A-7^T shared the highest 16S rRNA gene sequence similarity with A. rivipollensis P2G1^T (99.7% and 99.8%, respectively), while strain A-8^T exhibited 99.7% identity with A. media RM^T. Together with morphological, physiological, and biochemical data, genome-based analyses provided additional evidence for species differentiation. Digital DNA–DNA hybridization (dDDH; 56.8−65.9%) and average nucleotide identity (ANI; 94.2–95.7%) values fell below the species delineation thresholds, confirming that these isolates represent distinct taxa. Pathogenicity assays using greater wax moth (Galleria mellonella) larvae demonstrated strain-specific virulence profiles. Further genomic analyses identified biosynthetic gene clusters for nonribosomal peptides (NRPs) and ribosomally synthesized and post-translationally modified peptides (RiPPs), which often have roles in secondary metabolite production. Ecological analyses, based on genomic comparisons and metagenomic database searches, revealed the adaptability of the strains to diverse habitats, including freshwater, wastewater, and activated sludge. Based on the genetic and phenotypic data, the novel taxa Aeromonas ichthyocola sp. nov. A-5ᵀ (LMG 33534ᵀ = DSM 117488ᵀ), Aeromonas mytilicola sp. nov. A-7ᵀ (LMG 33536ᵀ = DSM 117490ᵀ), and Aeromonas mytilicola subsp. aquatica subsp. nov. A-8ᵀ (LMG 33537ᵀ = DSM 117493ᵀ) are proposed.

Background/Objectives: Transfusion-Related Immunomodulation (TRIM) is a complex biological phenomenon that develops following allogeneic blood transfusions. Exosomes released from stored red blood cell concentrates (RBC) may be a potential mediator of TRIM. This study aims to analyze the effects of exosomes on T cell proliferation and regulatory T cell (Treg) differentiation. Methods: RBC concentrates obtained from six healthy donors were divided into non-leukoreduced (NR) and leukoreduced (LR) units. Exosomes were isolated from these RBCs by ultracentrifugation. Allogeneic and autologous exosome pools were prepared. Peripheral blood mononuclear cells (PBMCs) were cultured with exosome pools (with 0.2, 1, or 5 μg doses) under allogeneic or autologous conditions. T-cell proliferation and Tregs were assessed by flow cytometry. Results: Total exosomal protein content increased during storage, with significantly higher levels in NR-RBC derived exosomes (NR-Exo) than LR-RBC derived exosomes (LR-Exo). NR-Exos significantly enhanced both CD4⁺ and CD8⁺ T cell proliferation, predominantly in allogeneic cultures. The proliferative effect was observed at different doses. In contrast, exosome treatment did not promote expansion of Treg populations. Instead, autologous cultures demonstrated reduced frequencies of CD8⁺ Tregs and CD39-expressing Tregs, whereas allogeneic cultures showed minimal changes. Moreover, leukoreduction attenuated exosome-mediated T-cell proliferation. Conclusions: RBC-Exos preferentially enhance effector T cell proliferation under allogeneic conditions, particularly when isolated from NR-RBC units. Tregs tended to decrease in both the autologous and leukoreduced groups. These findings suggest that RBC-Exos support both immunosuppressive effects and immune activation. However, the characteristics of the RBC and the transfusion (allogeneic/autologous and leukoreduced/non-leukoreduced) are considered the key factors in observing these effects.