Search Results (400)

Alexandrium spp. blooms and paralytic shellfish poisoning pose serious economic threats to coastal communities and aquaculture. This study evaluated the removal efficiency of two Alexandrium minutum strains using natural kaolinite clay (KNAC) and kaolinite with polyaluminum chloride (KPAC) at three concentrations (0.1, 0.25, and 0.3 g L⁻¹), two pH levels (7 and 8), and two cell densities (1.0 and 2.0 × 10⁷ cells L⁻¹) in seawater. PAC significantly enhanced removal, achieving up to 100% efficiency within two hours. Zeta potential analysis showed that PAC imparted positive surface charges to the clay, promoting electrostatic interactions with negatively charged algal cells and enhancing flocculation through Van der Waals attractions. In addition, the study conducted a cost estimate analysis and found that treating one hectare at 0.1 g L⁻¹ would cost approximately USD 31.75. The low KPAC application rate also suggests minimal environmental impact on benthic habitats. Full article

Fibrocapsa japonica (Raphidophyceae) is a cosmopolitan species frequently associated with harmful algal blooms (HABs) and fish mortality events, representing a potential threat to aquaculture and coastal ecosystems. This study provides the first comprehensive morphological, phylogenetic, pigmentary, and toxicological characterization of F. japonica strains isolated from Argentina. Light and transmission electron microscopy confirmed key diagnostic features of the species, including anterior flagella and the conspicuous group of mucocyst in the posterior region. Phylogenetic analysis based on the LSU rDNA D1–D2 region revealed monophyletic relationships with strains from geographically distant regions. Pigment analysis by HPLC identified chlorophyll-a (62.3 pg cell⁻¹) and fucoxanthin (38.4 pg cell⁻¹) as the main dominant pigments. Cytotoxicity assays using RTgill-W1 cells exposed for 2 h to culture supernatants and intracellular extracts showed strain-specific effects. The most toxic strain (LPCc049) reduced gill cell viability down to 53% in the supernatant exposure, while LC₅₀ values ranged from 1.6 × 10⁴ to 4.7 × 10⁵ cells mL⁻¹, depending directly on the strain and treatment type. No brevetoxins (PbTx-1, -2, -3, -6, -7, -8, -9, -10, BTX-B1 and BTX-B2) were detected by LC–MS/MS, suggesting that the cytotoxicity may be linked to the production of reactive oxygen species (ROS), polyunsaturated fatty acids (PUFAs), or hemolytic compounds, as previously hypothesized in the literature. These findings offer novel insights into the toxic potential of F. japonica in South America and underscore the need for further research to elucidate the mechanisms underlying its ichthyotoxic effect. Full article

Studies on plant extracts as growth promoters and immunostimulants have shown promising results. However, their effects on fish health and growth remain unclear. This study evaluated the in vitro and in vivo effects of Eucalyptus globulus pyroligneous extract (PE) on Nile tilapia. In vitro, minimal inhibitory and bactericidal concentration (MIC and MBC) and antibiogram analyses showed that PE could eliminate key bacterial strains affecting fish and human health, but only if its volatile components were preserved. In vivo, Oreochromis niloticus juveniles were fed diets containing 0.5% and 1% PE. We assessed fish hematology, phagocytosis, survival against Streptococcus agalactiae, and growth parameters. Fish fed 1% PE had lower erythrocyte and lymphocyte counts but higher neutrophil levels than controls. Their phagocytic capacity was significantly enhanced compared to both the control and 0.5% groups. However, the 0.5% PE group had a higher phagocytic index than both the control and 1% groups. No protection against S. agalactiae or significant effects on growth were observed. In conclusion, distilled E. globulus PE shows potential as an immunostimulant for fish. However, further studies are needed to preserve its volatile compounds and optimize its use in aquaculture. Full article

Vibrio parahaemolyticus (V. parahaemolyticus) is a preeminent seafood-borne pathogen, imposing significant economic burdens on global aquaculture. The escalating prevalence of multidrug-resistant strains has accentuated the critical urgency for developing sustainable biocontrol strategies. In this study, a bacteriophage designated vB_VPAP_XY75 (XY75) was isolated and biologically characterized to establish an effective control against V. parahaemolyticus. XY75 exhibited remarkable specificity toward V. parahaemolyticus, effectively lysing 46.2% of the target strains while showing no lytic activity against non-target bacterial species. Morphological characterization confirmed its taxonomic assignment to the Myoviridae family, featuring an icosahedral head (40 ± 2 nm) and contractile tail (60 ± 2 nm). XY75 demonstrated strong environmental tolerance, remaining stable at pH 4–11 and temperatures as high as 50 °C. At an optimal multiplicity of infection (MOI = 0.01), XY75 achieved a peak titer of 8.1 × 10¹⁰ PFU/mL, a 5 min latent period, and burst size of 118 PFU/cell. Critically, XY75 reduced V. parahaemolyticus in salmon by more than 5.98 log CFU/g (99.9%) within 6 h at 4 °C, demonstrating exceptional cold tolerance and lytic activity. Genomic analysis confirmed that no virulence or antibiotic resistance genes were present. These results establish XY75 as a safe and efficacious biocontrol candidate for seafood preservation, with particular utility under refrigerated storage conditions. Full article

Quorum quenching (QQ) is of interest for potential application as a sustainable strategy for bacterial disease control via communication interruption. The QQ enzyme can be used as a good alternative antagonist to combat antibiotic abuse and bacterial resistance. Here, genomic DNA sequencing was performed on N-acyl homoserine lactonase from the deep-sea strain Bacillus velezensis DH82 with Cluster of Orthologous Groups of proteins (COGs) annotation. The homologous sequences with β-lactamase domain-containing protein were predicted to be potential QQ enzymes and were cloned and expressed to study their quorum quenching properties by comparing them with the reported enzyme AiiA_3DHB. The experimental results of enzyme activity analysis and steady-state kinetics, as well as enzyme structure and substrate docking simulations and predictions, all consistently demonstrated that YtnP_DH82 presented superior enzyme structural stability and higher degradation efficiency of N-acyl homoserine lactones than AiiA_DH82 under the effects of pH, and temperature, and performed better on short -chain and 3-O-substituted AHSLs. The findings revealed the structural and biochemical characterization of YtnP_DH82 from the deep sea, which provide the capacity for further application in sustainable aquaculture as an alternative to antibiotics. Full article

The yellowtail kingfish (Seriola aureovittata), a commercially important marine species, encounters significant survival challenges under low-temperature conditions during winter aquaculture. To elucidate its molecular adaptation mechanisms, this study employed RNA-Seq to analyze transcriptional responses in juvenile muscle tissues under acute cold stress (10 °C) at 0, 6, 12, and 24 h. Differential gene expression analysis revealed time-dependent patterns, with 269, 863, and 984 differentially expressed genes (DEGs) identified at 6, 12, and 24 h, respectively. Key pathways were identified, including lipid metabolism, carbohydrate metabolism, and stress response. Sestrin3 upregulation implicated AMPK-mediated energy homeostasis in cold adaptation. These findings provide novel insights into the molecular strategies underlying cold adaptation in yellowtail kingfish, offering potential targets for breeding cold-resistant strains and improving aquaculture resilience. Full article

Aeromonas spp. are opportunistic pathogens that are widely distributed in water sources, with several species being associated with fish and human diseases. We have previously identified an Aeromonas AB005 isolate from diseased Acipencer baerii. This isolate was identified as A. hydrophila based on the 16S rRNA and gyrB gene sequences. However, this novel strain does not produce indole and tested negative for ornithine decarboxylase and d-xylose fermentation—differences that set it apart from typical A. hydrophila strains. In the present study, this strain was subjected to whole-genome sequencing and compared with the genomes of the type strain (Aeromonas hydrophila ATCC 7966^T) and other Aeromonas spp. Comprehensive genome analysis suggests that AB005 represents a distinct species within the genus. The draft genome of the AB005 strain comprises 4,780,815 base pairs with a GC content of 61.2% and contains 6104 predicted protein-coding sequences along with numerous genes implicated in antibiotic resistance. The core/pan-genome analysis reveals extensive genetic diversity, indicative of a dynamic genomic structure. These findings collectively underscore the taxonomic distinction of the AB005 strain as a novel species and highlight its potential pathogenic implications in aquaculture and public health settings. Full article

Proteus vulgaris is an emerging multidrug-resistant (MDR) foodborne pathogen that poses a significant threat to food safety and public health, particularly in aquaculture systems where antibiotic use may drive resistance development. Despite its increasing clinical importance, the genomic mechanisms underlying antimicrobial resistance (AMR) and virulence transmission in foodborne Proteus vulgaris remain poorly understood, representing a critical knowledge gap in One Health frameworks. To investigate its AMR and virulence transmission mechanisms, we analyzed strain P3M from Penaeus vannamei intestines through genomic island (GI) prediction and comparative genomics. Our study provides the first comprehensive characterization of mobile genetic elements in aquaculture-derived Proteus vulgaris, identifying two virulence-associated GIs (GI12/GI15 containing 25/6 virulence genes) and three AMR-linked GIs (GI7/GI13/GI16 carrying 1/1/5 antibiotic resistance genes (ARGs)), along with a potentially mobile ARG cluster flanked by IS elements (tnpA-tnpB), suggesting horizontal gene transfer capability. These findings elucidate previously undocumented genomic mechanisms of AMR and virulence dissemination in Proteus vulgaris, establishing critical insights for developing One Health strategies to combat antimicrobial resistance and virulence in foodborne pathogens. Full article

The “milky disease” in Chinese mitten crabs (Eriocheir sinensis), caused by Metschnikowia bicuspidata, poses significant threats to aquaculture, though its pathogenic mechanisms remain poorly understood. This study employs transcriptomic sequencing to analyze gene expression changes in Metschnikowia bicuspidata under hemocyte challenge, iron overload (1 mmol/mL), and combined stress, with functional validation through Common in Fungal Extracellular Membrane (CFEMgene) overexpression strains. Key findings reveal that (1) hemocyte challenge activated base excision repair (−log₁₀[P] = 7.58) and ribosome biogenesis pathways, indicating fungal adaptation through DNA repair and enhanced protein synthesis to counter host immune attacks (e.g., ROS-mediated damage). (2) Iron overload induced glutathione metabolism and pentose phosphate pathway enrichment, demonstrating mitigation of ferroptosis through NADPH/GSH antioxidant systems and autophagy/proteasome coordination. (3) Under combined stress, ribosome biogenesis (−log₁₀[P] = 1.3) and non-homologous end-joining pathways coordinated DNA repair with stress protein synthesis, complemented by vacuolar V-ATPase-mediated iron compartmentalization. (4) CFEM genes showed significant upregulation under hemocyte stress, with overexpression strains exhibiting enhanced biofilm formation (35% increased MTT cytotoxicity) and infectivity (40% higher infection rate), confirming CFEM domains mediate pathogenesis through iron homeostasis and virulence factor production. This work elucidates how M. bicuspidata employs metabolic reprogramming, oxidative stress responses, and CFEM-mediated iron regulation to establish infection, providing critical insights for developing targeted control strategies against milky disease. Full article

The research on the effect of feed with probiotic additives on the growth and functional state of young steelhead salmon (Salmo gairdneri) is presented in this study. For the first time, target strains selected not only by antagonism to pathogens but also by their ability to produce lytic enzymes or secondary metabolites with antioxidant activity were used to create probiotic preparations for aquaculture. This study presents findings showing that groups of fish fed probiotic feeds showed an improved growth performance and higher survival rate compared to the control. It was noted that the weights of fish in the first variant and the second variant of the experiment were higher by 8.8% and 6.8%, respectively. This research showed that juvenile steelhead salmon reared with probiotic-supplemented feeds had an improved ability to survive in high salinity and sublethal temperatures. This indicates that probiotics may play a significant role in enhancing the adaptive system of fish. Full article

Grass carp in aquaculture exhibited symptoms of bacterial infection leading to mortality. To investigate the cause of the disease and control grass carp infections, samples from diseased grass carp were collected, and a bacterial strain named XH-1 was isolated from the internal organs of the infected fish. Artificial infection experiments were conducted to determine whether the isolated strain XH-1 was the pathogenic bacterium. The biological characteristics of the isolated strain were studied through a 16S rRNA sequence analysis, physiological and biochemical identification, and phylogenetic tree construction. Extracts from 14 traditional Chinese herbs were tested to evaluate their bacteriostatic and bactericidal effects on the isolated strain. The regression infection experiment confirmed that the isolated strain XH-1 was the pathogenic bacterium causing the grass carp disease. Biological characterization studies identified the bacterium as Aeromonas veronii, which is clustered with A. veronii MW116767.1 on the phylogenetic tree. Among the 14 Chinese herbal extracts, Lignum sappa, Pericarpium granna, Artemisia argyi, Scutellaria baicalensis Georgi, Coptis chinensis, and Artemisiacapillaris thunb exhibited significant bacteriostatic effects on XH-1. Lignum sappa showed the highest sensitivity to A. veronii, with the largest inhibition zone diameter, and its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were 7.813 mg/mL and 15.625 mg/mL, respectively. As the concentration of Lignum sappa extract increased, its bacteriostatic and bactericidal effects strengthened. When the concentration exceeded 14 mg/mL, it maintained strong bactericidal activity over 32 h. This study on A. veronii XH-1 provides theoretical insights for the prevention of grass carp aquaculture diseases and the use of traditional Chinese herbs for treatment. Full article

Some Vibrio parahaemolyticus strains cause translucent post-larvae disease (Vp_TPD), leading to significant economic losses in shrimp farming. We aimed to identify whether a mixture of natural antimicrobials, AuraAqua (Aq), can protect white-leg shrimp (Penaeus vannamei) against the lethal effects of Vp_TPD and to understand its biological mode of action. Herein, we demonstrate that Aq, an antimicrobial mixture composed of a blend of organic acids, citrus, and olive extracts, suppressed Vp_TPD virulence at sub-inhibitory concentrations and conferred robust protection to shrimp. The minimum inhibitory and bactericidal concentrations against the Vp_TPD isolate were at 0.05% and 0.2%, respectively. At 0.05–0.1%, Aq reduced bacterial growth and downregulated six major virulence genes (vhvp-1, vhvp-2, vhvp-3, pirA_Vp, pirB_Vp, pirAB_Vp), while leaving metabolic ldh expression unaltered. Parallel in vitro assays revealed diminished adhesion of Vp_TPD to primary shrimp gut and hepatopancreas epithelial cells and a ≈50% reduction in infection-induced extracellular H₂O₂, indicating an antioxidant effect. The treatment also triggered a time-dependent surge in extracellular alkaline phosphatase (ALP) activity, consistent with membrane permeabilization. In vivo, a challenge of post-larvae with 10⁴ CFU/mL Vp_TPD resulted in 91% mortality after 45 h; co-treatment with 0.1% and 0.2% Aq reduced mortality to ≈12% and ≈6%, respectively, while 1% Aq achieved ≈98% survival. The clinical protection test confirmed that 0.1% Aq preserved high survival across four pathogen inocula (10¹–10⁴ CFU/mL). Conclusively, Aq destabilized the pathogen and therefore transcriptionally silenced multiple virulence determinants, translating into significant in-pond protection for controlling Vp_TPD for shrimp aquaculture. Full article

Aeromonas salmonicida is an age-old fish pathogen widely distributed in seawater and freshwater environments that causes significant economic losses to the global aquaculture industry. Genetic mutations and the emergence of thermophilic strains are factors in the continuous expansion of A. salmonicida’s host range. Beyond infecting fish, A. salmonicida poses a potential threat to mammalian and human health. This review synthesizes recent global research advances concerning A. salmonicida, encompassing strain characteristics, genomic features, virulence factors, and pathogenic mechanisms, as well as the clinical manifestations in infected fish and mammals, and discusses prevention and treatment methods. Particular emphasis is placed on evaluating the potential prophylactic roles of Chinese herbs and bacteriophages against A. salmonicida infection. Furthermore, the review provides perspectives on future research directions, diagnostics, and disease management, informed by contemporary domestic and international studies on this pathogen. Full article

The shift toward plant-based feeds in aquaculture necessitates a search for probiotics to improve the digestibility of such feeds and fish growth. This study characterizes four Bacillus strains for their probiotic potential in carp (Cyprinus carpio). Strains isolated from river sediments underwent in vitro screening for proteolytic/amylolytic activity, antibiotic sensitivity, and biofilm formation. Whole-genome sequencing was performed and functional annotation identified probiotic-related genes. All strains were identified as Bacillus velezensis and harbored genes providing thermal, osmotic, and oxidative stress resistance, alongside enzymes and bioactive metabolite synthesis pathways. Two non-antagonistic strain pairs were solid-phase cultivated on soybeans and incorporated into carp feed (0.1% w/w) for a 76-day trial, and growth metrics and gene expression were analyzed in juvenile fish. Group 1 (strains MT14 + MT42) exhibited a 40.75% higher biomass increase than the control group while Group 2 (strains MT141 + MT142) exhibited a 56.62% higher biomass growth. No significant gene expression changes occurred in juveniles, though MT141 + MT142 transiently modulated fry expression profiles. Therefore, these Bacillus velezensis strains synergistically enhance growth in carp that are fed plant-rich diets, highlighting their viability as aquaculture probiotics. Full article

Vibrio species are among the primary pathogenic bacteria affecting abalone aquaculture, posing significant threats to farming practices. Current clinical control predominantly relies on antibiotics, which can result in antibiotic residues in both abalone and the surrounding marine environments. Lactobacillus plantarum (LP) has been shown to release bioactive antagonistic substances and exhibits potent inhibitory effects against marine pathogenic bacteria. This study aimed to screen and characterize the probiotic properties of LP strains isolated from rice wine lees to develop a novel biocontrol strategy against Vibriosis in abalone. The methods employed included selective media cultivation, streak plate isolation, and single-colony purification for strain screening, followed by Gram staining, 16S rDNA sequencing, and phylogenetic tree construction using MEGA11 for identification. The resilience, antimicrobial activity, and in vivo antagonistic efficacy of the strains were evaluated through stress tolerance assays, agar diffusion tests, and animal experiments. The results demonstrated the successful isolation and purification of four LP strains (NDMJ-1 to NDMJ-4). Phylogenetic analysis revealed closer genetic relationships between NDMJ-3 and NDMJ-4, while NDMJ-1 and NDMJ-2 were found to be more distantly related. All strains exhibited γ-hemolytic activity, bile salt tolerance (0.3–3.0%), and resistance to both acid (pH 2.5) and alkali (pH 8.5), although they were temperature sensitive (inactivated above 45 °C). The strains showed susceptibility to most of the 20 tested antibiotics, with marked variations in hydrophobicity (1.91–93.15%) and auto-aggregation (13.29–60.63%). In vitro antibacterial assays revealed that cell-free supernatants of the strains significantly inhibited Vibrio parahaemolyticus, V. alginolyticus, and V. natriegens, with NDMJ-4 displaying the strongest inhibitory activity. In vivo experiments confirmed that NDMJ-4 significantly reduced mortality in abalone infected with V. parahaemolyticus. In conclusion, the LP strains isolated from rice wine lees (NDMJ-1 to NDMJ-4) possess robust stress resistance, adhesion capabilities, and broad antibiotic susceptibility. Their metabolites exhibit significant inhibition against abalone-pathogenic Vibrios, particularly NDMJ-4, which demonstrates exceptional potential as a candidate strain for developing eco-friendly biocontrol agents against Vibriosis in abalone aquaculture. Full article