Marine Biotechnology最新文献

This article aims to reveal the optimal peptide segment with antioxidant activity from Dalian Stichopus japonicus, investigate its anti-melanogenesis effect, and elucidate its mechanisms of action both in vitro and in vivo. The best antioxidant alcalase hydrolysates, identified by the previous screening of proteases, was isolated by ultrafiltration; it was found that the components with a molecular weight of ≤ 3 kDa exhibited the best activity. The chemical components were characterized using LC–MS/MS. Through molecular docking, GPIGF was identified as the peptide segment with the best antioxidant and melanogenesis-inhibitory activity. A search in the NCBI database revealed that GPIGF is a newly obtained natural oligopeptide. Further experiments with synthesized GPIGF in vitro showed that it effectively reduces cell apoptosis and damage, and inhibits the expression of melanin-related genes, including tyrosinase (TYR), and associated proteins TRP-1, TRP-2, and MITF. In vivo experiments with the zebrafish model demonstrated that GPIGF significantly inhibits AAPH-induced apoptosis in zebrafish larvae, reduces the production of ROS, and suppresses melanin generation on the skin surface without exhibiting embryotoxicity. This study provides a research foundation for the development of antioxidants from Dalian Stichopus japonicus, which could serve as natural whitening and anti-aging agents, supporting its integrated utilization and development.

DOPA decarboxylase (DDC) plays a crucial role in the physiological functions of animals by participating in the dopaminergic system. However, the functions of DDC in shellfish remain poorly understood. The Pacific oyster (Crassostrea gigas) is an extensively cultivated shellfish. In this study, we characterized a DDC gene, designated CgDDC, from C. gigas. The CgDDC gene encodes a protein that contains a Pyridoxal_deC domain, which features specific binding sites for pyridoxal-5’-phosphate (PLP) and L-DOPA. CgDDC exhibits a significantly higher expression level in the black shell oyster strain than the white strain. In vitro enzymatic reaction assays demonstrated that CgDDC catalyzes the conversion of L-DOPA to dopamine. In vivo experiments revealed that inhibiting CgDDC activity reduced the expression of genes associated with tyrosine metabolism. Furthermore, the knockdown of CgDDC caused a decline in cAMP level and reduced transcription of genes involved in the cAMP-mediated melanogenesis. Additionally, treatment with L-α-DOPA inhibited CgDDC enzyme activity and cAMP-mediated melanogenesis; however, dopamine supplementation countered this inhibition, maintaining gene expression and melanin content at baseline levels. Collectively, our findings suggest that CgDDC is intricately involved in regulating tyrosine metabolism and melanogenesis in C. gigas.

Coral reefs are essential for biodiversity and ecosystem services, yet they face threats like bleaching and reduced resilience due to rising seawater temperatures and land-based pollution. This study examined phosphate accumulation in calcareous sediments and its relationship with coral populations in Sekisei Lagoon, Okinawa Islands, Japan. Sediment samples from 117 sites were analyzed for exchangeable phosphate in seawater (EPS), which could be released from the calcareous sediments. The EPS levels were negatively correlated with coral densities for adults (Pocillopora, Acropora, Galaxea, Favia, Favites, Goniastrea, and Cyphastrea) and juveniles (Pocillopora, Montipora, Acropora, Galaxea, Favia, Favites, and Goniastrea). No significant correlation was found for Porites or Millepora. The EPS levels were positively correlated with coral bleaching and the abundance of Sargassaceae algae. High coastal EPS levels suggest main pollution sources from livestock and shrimp farming. The threshold above which EPS impacts coral bleaching and density was estimated at 0.3–0.7 µg/g, providing insights for coral reef conservation.

High temperature restricts the survival and growth of aquatic organisms. Probiotics have significant potential for mitigating the negative effects of temperature stress on fish. In this study, the American shad (Alosa sapidissima), a temperature-sensitive freshwater fish, was selected as the experimental paradigm to dissect the underlying mechanisms governing the interactions between the host and its microbiome, with a particular focus on the impact exerted by the probiotic Lactococcus lactis within a high-temperature setting. We evaluated the effects of probiotics on the growth and biochemistry of A. sapidissima by measuring relevant parameters and enzyme activities and conducted an integrated microbiome–transcriptome analysis to assess the impacts on the gut microbiota and uncover probiotic-regulated metabolic pathways. The findings of our research indicated that probiotics had beneficial effects on growth; the activities of enzymes such as LPS, T-SOD, and GSH-PX; and the gut microbial composition. Furthermore, the configuration of the intestinal microbiota underwent a transformation, as evidenced by the increased relative prevalence of bacteria with potential beneficial properties, including Bacillus, Lactococcus, and Clostridium. Liver transcriptomic analysis revealed 586 differentially expressed genes (DEGs). The expression of immune-related genes (nfil3-2, il17d, and leap2) and lipid metabolism-related genes (pla2g3 and sc5d) was strongly upregulated. KEGG enrichment analysis revealed that the DEGs were predominantly clustered within metabolic pathways such as circadian rhythm and fatty acid degradation. This study revealed that probiotics enhanced intestinal bacterial diversity and eased stress by regulating the circadian rhythm, immunity, and lipid metabolism under high-temperature conditions. This study provides a reference for the use of probiotics in A. sapidissima at high temperatures.

The increasing plastic production causes serious problems in the marine environment, and the main source of plastic waste comes from the fishing and aquaculture industries. Although there have been various efforts to develop aquaculture equipment with marine biodegradable plastics, an urgent need is to develop an assay to evaluate their biodegradation in aquaculture environments. This study focused on evaluating the biodegradation of biomass plastic in recirculating aquaculture systems (RAS) that mimic freshwater, brackish water, and saltwater aquacultures. The methods used to assess biomass plastic biodegradability included changes in physical properties, weight loss, biochemical oxygen demand, and microbial community investigation using poly(butylene succinate-co-adipate) (PBSA) as a model. Scanning electron microscopy studies indicated the erosion on the biomass plastic surface from 1 to 2 days in the RAS tank (salinity, 0–0.5%) harboring Nile tilapia (Oreochromis niloticus). 4′,6-Diamidino-2-phenylindole fluorescence microscopy confirmed the presence of the microorganisms on the PBSA surface. The microorganisms in RAS tanks degraded 11.6% of 1 g/L PBSA in 7 days, demonstrating their biodegradation potential. 16S rRNA gene sequencing showed that Pseudomonas plays a major role as an early decomposer in the biodegradation process within 24 h. A multifaceted analytical method that provides sufficient evidence was developed to show that the erosion on the PBSA surface in RAS tanks results from biodegradation. The ability of RAS to control various aquatic environments (pH, salinity, temperature, and bacterial density) makes it suitable for testing the marine biodegradability of biomass plastics for use in aquaculture and fishery industries.

T-box transcription factor 2 (TBX2) plays a critical role in various biological processes, including cell cycle regulation, malignant transformation, and regulating melanogenesis. In our previous study, we identified a Crassostrea gigas TBX2 (CgTBX2) and investigated its regulatory role in melanin production in oysters. Here, the mechanism of CgTBX2 in regulating cell proliferation was investigated. First, we found that CgTBX2 promoted the proliferation of mouse melanoma (B16F10) cells. CgMITF-X3, a 1347 bp transcript isoform of MITF from C. gigas, was then cloned and it was also found to promote cell proliferation. Co-transfection of CgTBX2 and CgMITF-X3 into B16F10 cells had a synergistic effect on cell proliferation, suggesting that CgMITF-X3 enhanced the function of CgTBX2 in promoting cell proliferation. CgMITF-X3 promoted the transcriptional activation of CgTBX2 by directly binding to the TCTCACGCGG sequence in the CgTBX2 promoter region. In addition, CgTBX2 and CgMITF-X3 proteins were co-located in the nucleus, indicating that these two proteins may perform a certain function collectively in the nucleus. Taken together, our findings revealed that CgTBX2 is directly activated by CgMITF-X3 at the transcriptional level, and both CgTBX2 and CgMITF-X3 facilitate cell proliferation.

The ploidy detection is crucial for the oyster industry. The objective of this study was to develop a method that verifies ploidy of the triploid Pacific oyster Crassostrea gigas by analyzing the diversity of triploid through microsatellite multiplex PCRs using fluorescent universal primers. We developed four information-rich multiplex PCR panels, comprising a total of 12 genomic microsatellites located in the genome of the C. gigas, distributed across seven chromosomes with an average of 14 alleles per locus. Each panel used M13(-21) primers labeled with specific fluorochrome dyes, and the forward primers for each locus were appended with M13(-21) sequences. We validated the approach to infer ploidy using flow cytometry as a reference, finding > 95% agreement between these methods, and demonstrated its potential utility to infer aneuploidy. Genotyping of 496 triploid samples from eight populations yielded 10 or more alleles per locus in 99.63% of samples in a single capillary electrophoresis. The correct assignment of triploidy depends on the number of markers with three unique allele fragments (MNM). Using semi-strict criteria of three unique alleles at one or more loci, the detection accuracy rate was 95.26% for triploids. Using the strict criteria of three unique alleles at two or more loci, the detection accuracy rate was 98.34%. Populations with reduced genetic diversity due to selective breeding were better suited for the semistrict criterion, maximizing triploid detection. And cultured populations were more suitable for evaluation using the strict criteria, which effectively reduced false-positive diploid assignment and increased triploid detection accuracy. The markers developed in this study were highly polymorphic and effective for assessing genetic diversity and distinguishing populations, providing a reliable tool for triploid detection and analysis in oyster breeding.

Flow velocity is a critical environmental factor influencing the growth, energy metabolism, and physiological health of aquaculture species. This study investigated the physiological and molecular responses of spotted sea bass (Lateolabrax maculatus) under experimental conditions simulating flow velocities typical of land-based recirculating aquaculture systems (RAS) and deep-sea cage systems. High flow velocities (HFV, 0.35–0.65 body lengths per second [BL/s]) enhanced growth performance compared to low flow velocity (LFV, 2.28–2.85 BL/s) conditions. Histological analysis revealed reduced hepatic lipid accumulation under HFV, while LFV promoted lipid storage. Serum analyses showed elevated antioxidant enzyme activity in the LFV group but higher oxidative stress markers in the HFV group. Transcriptomic profiling identified foxo3 as a key regulatory hub orchestrating metabolic and oxidative stress adaptations. Genes associated with oxidative damage repair, lipid catabolism, and glucose metabolism were significantly enriched under hydrodynamic stress. Enrichment of the FoxO signaling pathway highlighted its central role in mediating oxidative stress mitigation and energy mobilization. These findings demonstrate the dual effects of flow velocity, where higher velocities promote growth and metabolic activity at the cost of oxidative stress, and lower velocities conserve energy while maintaining oxidative stability. Tailored flow velocity conditions can optimize fish welfare and productivity across aquaculture systems. Future studies should investigate the systemic effects of hydrodynamic stress using multi-omics approaches to advance sustainable aquaculture practices.

Coastal hypoxia is an increasing environmental concern affecting marine ecosystems globally, particularly impacting benthic organisms such as bivalves. Although previous studies focused on the physiological responses of bivalves to hypoxic stress, the role of resident bacteria in the host response to hypoxia remains poorly understood. This study investigated changes in the resident bacterial communities in the gills and hepatopancreatic tissues of the ark shell (Anadara kagoshimensis) under hypoxic conditions. Specimens were assigned to three treatment groups: untreated control, hypoxia, and hypoxia with chloramphenicol supplementation (5.0 mg/L). After 3 days, specimens exposed to hypoxia exhibited black precipitation in the culture water, whereas antibiotic treatment reduced these effects. Amplicon sequencing revealed distinct bacterial communities between the tissues, with Arcobacteraceae and Alkalispirochaetaceae dominating in the gills and Metamycoplasmataceae being predominant in the hepatopancreas. The hepatopancreas displayed greater bacterial community changes than the gills under hypoxic conditions, including an increase in the abundance of Metamycoplasmataceae. The predicted metabolic functions suggested that these bacteria contribute to iron sulfide precipitation through sulfate reduction and iron respiration. The antibiotic-treated group displayed bacterial communities more similar to those of the control group, confirming the effectiveness of chloramphenicol in suppressing bacterial changes under hypoxia. This study provided new insights into tissue-specific bacterial responses to hypoxia in A. kagoshimensis and highlighted the potential role of Metamycoplasmataceae in the bivalve’s response to hypoxic stress.

Hepcidin is a cysteine-rich antimicrobial peptide that plays an important role in fish immunity. In the current study, we report a novel isoform of hepcidin (Jd-Hep) from Sin croaker, Johnius dussumieri, with an open reading frame (ORF) of 258 nucleotide bases that encodes 85 amino acids containing a signal peptide (24 amino acids), a prodomain (35 amino acids) and a biologically active mature peptide (26 amino acids). Phylogenetic tree analysis showed that J. dussumieri hepcidin belonged to the HAMP2 cluster of hepcidin. The tissue distribution showed that the expression of hepcidin was highest in the liver in wild-caught J. dussumieri. The mature peptide mJd-Hep was recombinantly expressed in a prokaryotic host, E. coli Rosetta-gami™B (DE3) pLysS cells, and the peptide was isolated and purified. The recombinant peptide, rJd-Hep, exhibited notable antibacterial activity against aquatic pathogens such as Aeromonas hydrophila, Vibrio parahaemolyticus, Vibrio harveyi, Vibrio alginolyticus, Vibrio proteolyticus, and Vibrio fluvialis. The mode of action of the peptide was proven to be membrane-based (pore formation and depolarization). The rJd-Hep was found to be non-hemolytic to hRBCs and non-cytotoxic to the mammalian cell line. The peptide showed 85% growth inhibition of cancer cell line, MCF-7. These findings expand our knowledge of the potential application of hepcidin in aquaculture as a therapeutic agent.