Marine Biotechnology最新文献

Bacteria of the phylum Verrucomicrobia is widely distributed in diverse ecological environments. Their limited cultivability has greatly caused the significant knowledge gap surrounding their secondary metabolites and their mediating ecological functions. This study delved into the diversity and novelty of secondary metabolite biosynthetic gene clusters (BGCs) of Verrucomicrobia by employing a gene-first approach to investigate 2323 genomes. A total of 7552 BGCs, which encompassed 3744 terpene, 805 polyketide, 773 non-ribosomal peptide gene clusters, and 1933 BGCs of other biosynthetic origins, were identified. They were further classified into 3887 gene cluster families (GCFs) based on biosynthetic gene similarity clustering, of which only six GCFs contained reference biosynthetic gene clusters in the Minimum Information about a Biosynthetic Gene Cluster (MIBiG), indicating the striking novelty of secondary metabolites in Verrucomicrobia. Notably, 37.8% of these gene clusters were harbored by unclassified species of Verrucomicrobia phyla, members of which were highly abundant in soil environments. Furthermore, our comprehensive analysis also revealed Luteolibacter and Methylacidiphilum as the most prolific genera in terms of BGC abundance and diversity, with the discovery of a conservative and new NRPS-PKS BGC in Luteolibacter. This work not only unveiled the biosynthetic potential and genetic diversity of secondary metabolites of Verrucomicrobia but also provided a fresh insight for the exploration of new bioactive compounds.

5-Aminolevulinic acid (5-ALA) is an endogenous non-protein amino acid and has been used as a new type of growth promoter in aquaculture feed. This study explored the effects of 5-ALA on growth and intestinal health in juvenile shrimp, Litopenaeus vannamei. Shrimps were fed diets containing five different 5-ALA levels (0, 15, 30, 45, and 60 g/t) for 90 days. A concentration of 45 g/t 5-ALA significantly improved growth metrics, including the specific growth rate, protein efficiency, and feed conversion (P < 0.05). The optimal concentration of 5-ALA was 38.3 g/t, as indicated by broken-line regression. Dietary supplementation with 5-ALA increased the crude protein content of whole shrimp, but had no significant effect on the moisture, ash, or crude lipid content (P > 0.05). Suitable supplementation of 5-ALA (45 g/t, 60 g/t) improved the activities of the digestive enzymes alpha-amylase, pepsin, trypsin, and lipase, thus promoting digestion and absorption. Shrimp fed with 45 g/t 5-ALA had increased levels of essential amino acids in the muscles and a higher proportion of polyunsaturated fatty acids in the hepatopancreas. Supplementation with 45 or 60 g/t 5-ALA upregulated the expression of genes related to growth and molting, including chitinase, ecdysone receptor, retinoic X receptor, calcium/calmodulin-dependent protein kinase I, heat shock protein 60, and heat shock protein 70. Moreover, dietary supplementation with 5-ALA affected the abundance of intestinal flora, increased the number of beneficial bacteria, and improved intestinal health. These results indicated that 5-ALA may significantly benefit shrimp health and aquaculture productivity, providing a novel theoretical basis for further research into 5-ALA as a dietary supplement.

Pyropia yezoensis is an important economic macroalga widely cultivated in the East Asia countries of China, Korea, and Japan. The ATP-binding cassette (ABC) transporter gene family is one of the largest transporter families in all forms of life involved in various biological processes. The characteristics of ABC transporter genes in P. yezoensis (PyABC) and their functions in stress resistance, however, remain largely unknown. In this study, PyABCs were identified and characterized their expression patterns under low-temperature stress. A total of 48 PyABCs transporters were identified and divided into eight subfamilies, which are mostly predicted as membrane-binding proteins. The cis-elements of phytohormone and low-temperature response were distinguished in promoter sequences of PyABCs. Transcriptome analysis showed that PyABCs are involved in response to low-temperature stress. Among them, 12 PyABCs were significantly up-regulated after 24 h of exposure to low temperature (2 °C). Further quantitative RT-PCR analysis corroborated the highest expression happened at 24 for detected genes of PyABCC8, PyABCF3, and PyABCI1, extraordinarily for PyABCF3, and followed by decreased expression at 48 h. The expression of PyABCI1 was generally low in all tested strains. Whereas, in a strain of P. yezoensis with lower tolerance to low temperature, the expression was observed higher in PyABCC1, PyABCC8, and remarkably high in PyABCF3. This study provided valuable information on ABC gene families in P. yezoensis and their functional characteristics, especially on low-temperature resistance, and would help to understand the adaptive mechanisms of P. yezoensis to adverse environments.

The excessive use of antibiotics in aquaculture favors the natural selection of multidrug-resistant bacteria, and antimicrobial peptides (AMPs) could be a promising alternative to this problem. The most studied AMPs in teleost fish are piscidins, hepcidins, and β-defensins. In this work, we have found a new gene (defb2) encoding a type 2 β-defensin in the genome of gilthead seabream, a species chosen for its economic interest in aquaculture. Its open reading frame (192 bp) encodes a protein (71 amino acids) that undergoes proteolytic cleavage to obtain the functional mature peptide (42 amino acids). The genetic structure in three exons and two introns and the six characteristic cysteines are conserved as the main signature of this protein family. In the evolutionary analysis, synteny shows a preservation of chromosomal localization and the phylogenetic tree constructed exposes the differences between both types of β-defensin as well as the similarities between seabream and European seabass. In relation to its basal expression, β-defensin 2 is mostly expressed in the intestine, thymus, skin, and gonads of the gilthead seabream (Sparus aurata). In head kidney leucoytes (HKLs), the expression was very low and did not change significantly when stimulated with various immunocompetent agents. However, the expression was significantly down-regulated in the liver, head–kidney, and blood 4 h post-injection with the fish pathogen Vibrio harveyi. When infected with nodavirus, the expression was downregulated in brain at 7 days post-infection. These results denote a possible complementarity between the expression patterns of β-defensins and hepcidins. Further studies are needed to analyze gene duplications and expression patterns of β-defensins and describe their mechanism of action in seabream and other teleost fish.

The present study aimed to isolate a bioactive compound from Sri Lankan edible marine brown algae, Chnoospora minima, to manage diabetes. The de-polysaccharide crude methanolic extract was partitioned using hexane, chloroform, and ethyl acetate with increased polarity. The samples were subjected to determine the quantitative phytochemical analysis, antioxidants, and antidiabetic potentials. Further, the potent antidiabetic fraction was selected to isolate an active compound using bioactivity-guided fractionation. From the selected extract, the chloroform fraction exhibited comparatively high TPC (59.01 ± 1.86 mg GAE/g), TFC (5.14 ± 0.43 mg QE/g) and alkaloid content (2.79 ± 0.31 PE/g of extract). Crude methanol extract exhibited a potent DPPH activity (IC₅₀: 0.48 ± 0.01 mg/mL) whereas the ethyl acetate fraction elicited a maximum ABTS activity (IC₅₀: 0.064 ± 0.001 mg/mL) and a ferrous iron–chelating capacity (IC₅₀: 0.019 mg/mL). Similarly, the chloroform fraction exhibited the highest FRAP (20.34 ± 1.72 mg TE/g) and ORAC (19.72 ± 2.92 mg TE/g) capacities. The potent inhibitory activity of α-amylase (IC₅₀:3.17 ± 0.02 µg/mL) and α-glucosidase (IC₅₀: 1.99 ± 0.01 µg/mL) enzymes and glucose diffusion was observed in the chloroform fraction. Similarly, the chloroform extract exhibited a potent BSA-glucose (IC₅₀: 202.43 ± 5.71 µg/mL), BSA-MGO (IC₅₀: 124.30 ± 2.85 µg/mL) antiglycation model and reversing activities (EC_50BSAglucose: 98.99 ± 0.35 µg/mL; EC_50BSA-MGO: 118.89 ± 1.58 µg/mL). Depending on the hypoglycemic activity, fucoxanthin was isolated as the active compound which showed a notable change in the functional group. Molecular docking studies were conducted on the compound, and binding energy was observed to be − 6.56 kcal/mol and − 4.83 kcal/mol for α-amylase and α-glucosidase enzymes, respectively, which confirmed the hypoglycemic effect of the isolated compounds. However, more studies are required to understand the mechanistic insights of these observations.

Biopolymers are a versatile and diverse class of materials that has won high interest due to their potential application in several sectors of the economy, such as cosmetics, medical materials/devices, and food additives. In the last years, the search for these compounds has explored a wider range of marine organisms that have proven to be a great alternative to mammal sources for these applications and benefit from their biological properties, such as low antigenicity, biocompatibility, and biodegradability, among others. Furthermore, to ensure the sustainable exploitation of natural marine resources and address the challenges of 3R’s policies, there is a current necessity to valorize the residues and by-products obtained from food processing to benefit both economic and environmental interests. Many extraction methodologies have received significant attention for the obtention of diverse polysaccharides, proteins, and glycosaminoglycans to accomplish the increasing demands for these products. The present review gives emphasis to the ones that can be obtained from marine biological resources, as agar/agarose, alginate and sulfated polysaccharides from seaweeds, chitin/chitosan from crustaceans from crustaceans, collagen, and some glycosaminoglycans such as chondroitin sulfate and hyaluronic acids from fish. It is offered, in a summarized and easy-to-interpret arrangement, the most well-established extraction and purification methodologies used for obtaining the referred marine biopolymers, their chemical structure, as well as the characterization tools that are required to validate the extracted material and respective features. As supplementary material, a practical guide with the step-by-step isolation protocol, together with the various materials, reagents, and equipment, needed for each extraction is also delivered is also delivered. Finally, some remarks are made on the needs still observed, despite all the past efforts, to improve the current extraction and purification procedures to achieve more efficient and green methodologies with higher yields, less time-consuming, and decreased batch-to-batch variability.

Graphical Abstract

As a prerequisite for the success of embryo development, embryonic genome activation (EGA) is an important biological event in which zygotic gene products in the embryo are activated to replace maternal-derived transcripts. Although EGA has been extensively studied in a large number of vertebrates and invertebrates, there is a lack of information regarding this event in crustacean crab. In this study, the timing of EGA was confirmed by examining a transcriptomic dataset of early embryonic development, including mature oocytes and embryos through six early developmental stages, and signaling pathways associated with EGA were identified in the mud crab, S. paramamosain. The comprehensive transcriptomic data identified a total of 53,915 transcripts from these sequencing samples. Notable transcriptomic change was evident at the 1-cell stage, indicated by a 36% transcript number shift and a reduction in transcript fragment length, compared to those present in the mature oocytes. Concurrently, a substantial increase in the expression of newly transcribed transcripts was observed, with gene counts reaching 3485 at the 1-cell stage, indicative of the onset of EGA. GO functional enrichment revealed key biological processes initiated at the 1-cell stage, such as protein complex formation, protein metabolism, and various biosynthetic processes. KEGG analysis identified several critical signaling pathways activated during EGA, including the "cell cycle," "spliceosome," "RNA degradation", and "RNA polymerase", pathways. Furthermore, transcription factor families, including zinc finger, T-box, Nrf1, and Tub were predominantly enriched at the 1-cell stage, suggesting their pivotal roles in regulating embryonic development through the targeting of specific DNA sequences during the EGA process. This groundbreaking study not only addresses a significant knowledge gap regarding the developmental biology of S. paramamosain, especially for the understanding of the mechanism underlying EGA, but also provides scientific data crucial for the research on the individual synchronization of seed breeding within S. paramamosain aquaculture. Additionally, it serves as a reference basis for the study of early embryonic development in other crustacean species.

Induced pluripotent stem cells (iPSCs) are a new type of pluripotent cells reprogrammed from somatic cells back into an embryonic-like pluripotent state of stem cells to study development, disease and potential gene therapies. The induction and regulation mechanisms of iPSCs in fish are still unclear. By using the transfection technique, we investigated the crucial function of the OSKMNL factor co-expression for somatic reprogramming in the muscle cell line of large yellow croaker (Larimichthys crocea) (LYCMs) and successfully established a stable iPSCs line (Lc-OSNL-iPSCs). Stable culturing of iPSCs with high alkaline phosphatase activity and a stable karyotype was achieved. The qRT-PCR and immunofluorescence labeling results revealed that Lc-OSNL-iPSCs displayed a high expression level of pluripotent marker genes such as Nanog, Oct4, and Sox2. There were significant differences between Lc-OSNL-iPSCs, Lc-OSKMNL-iPSCs, and LYCMs, and the expression of several genes in maintaining cell pluripotency was up-regulated when the pluripotency signal pathway of stem cells was activated. The technical system for inducing iPSCs of Larimichthys crocea was constructed in this study. This system can serve as a basic model to understand germ cell differentiation mechanism, gender control, genetics, and breeding of large yellow croaker and a platform for studying iPSCs in fish. Interestingly, the acquired iPSCs serves as a useful material for the directional induction of muscle stem cells, thereby establishing the groundwork for obtaining "artificial fish" in the future.

Cyclin-dependent kinases (Cdks) are major molecules related to cell cycle regulation. Polyploidy can be caused by the production of unreduced gametes, which is often related to the abnormal cell cycle of germ cells. Here, we successfully constructed a cdk1 mutation line (cdk1^+/-) in zebrafish, a commonly used model organism. It showed that cdk1 depletion resulted in the generation of both polyploid and aneuploid embryos of WT♀ × cdk1^+/-♂ zebrafish. In addition to normal sperms (1N), the depletion of cdk1 in zebrafish also led to the production of some large-head 2N sperms and higher ploidy sperms. Results of bivalent analysis of testis and ultrastructure analysis of spermatogonia suggested that the production of these large-head sperms was due to spermatogonia chromosome doubling in cdk1^+/- zebrafish. Transcriptome analysis revealed aberrant expressions of some cell cycle and DNA replication-related genes in the early testis of cdk1^+/- zebrafish relative to WT zebrafish. Through STRING correlation analysis, we further proved that cdk1 depletion affected the mitosis process and endoduplication initiation of spermatogonia by regulating expressions of some proteins related to cell cycle (i.e., Espl1 and Pp1) and DNA replication (i.e., Orc1 and Rnaseh2b), thereby leading to the formation of unreduced sperms. This study provides important information on revealing the molecular mechanisms of unreduced gamete formation caused by cdk1 mutation. Meanwhile, it also provides an important reference for the creation of fish polyploid germplasm.

The severity, frequency, and duration of extreme events, in the context of global warming, have placed many marine ecosystems at high risk. Therefore, the application of methods that can mediate the impacts of global warming on marine organisms seems to be an emerging necessity in the near term. In this context, enhancing the thermal resilience of marine organisms may be crucial for their sustainability. It has been shown that the repeated time-limited exposure of an organism to an environmental stimulus modifies its response mode, thus enhancing resilience and allowing adaptation of the physiological and developmental phenotype to environmental stress. In the present study, we investigated the "stress memory" effect caused by heat hardening on Mytilus galloprovincialis cellular pathways to identify the underlying biochemical mechanisms that enhance mussel thermal tolerance. Heat hardening resulted in increased ETS activity and ATP production and increased autophagic performance at all elevated temperatures (24 °C, 26 °C, and 28 °C). Furthermore, at these increased temperatures, apoptosis and inflammation remain at significantly lower levels in pregnant individuals than in nonhardened individuals. Autophagy, as a negative regulator of apoptosis, may lead to decreased damage to surrounding cells, which in turn alleviates inflammatory effects. In conclusion, the exposure of mussels to heat hardening seems to provide a physiological response that enhances heat tolerance and increases cell survival through increased energy production and reduced cell death and inflammatory responses. The latter can be utilized for the management and conservation of aquatic species of economic value or endangered status.