Marine Biotechnology最新文献

Microorganisms in the digestive tract regulate the metabolism of host cells as well as stimulate the immune system of the host. If the microbiota is in good balance, it will promote the good health of the host. In this study, using 16S rRNA sequencing, we analyzed the microbiota of three groups of shrimp: a group of normal shrimp (control group), shrimp that were killed by infection with the white spot syndrome virus (WSSV) (susceptible group), and shrimp that survived WSSV infection (resistant group). The results showed that although the alpha diversity of the microbiota was barely affected by the WSSV, the bacterial communities in the three groups had different prevalences. The resistant group harbored significantly more bacteria than both the other groups. Remarkably, the resistant group had the greatest prevalence of the phylum Bacterioidetes, the families Rhodobacteraceae and Flavobacteriaceae, and the genus Nautella, suggesting their potential as biomarkers for shrimp resistance to WSSV infection. In addition, analysis of functional diversity in bacterial communities showed that the abundance of bacterial metagenomes in two groups infected with WSSV was mostly linked to metabolism and cellular processes. The susceptible WSSV group exhibited a significant reduction in amino acid metabolism. This result suggested that metabolism was the principal factor affecting the alteration in the microbiota after WSSV infection. This overview of the gut microbiota of shrimp infected with the WSSV offers crucial insights for aquaculture management and simplifies the use of control strategies in the future.

Sex determination is a fascinating area of research. To date, more than 20 master sex determination (SD) genes have been reported from vertebrate animals. With channel catfish (Ictalurus punctatus), much work has been conducted to determine its master SD gene, ranging from genetic linkage mapping, genome-wide association (GWA) analysis, genome sequencing, comparative genome analysis, epigenomic analysis, transcriptome analysis, and functional studies. Here in this mini review, we provide positional, expression, regulatory, and functional evidence supporting hydin (hydrocephalus-inducing protein or HYDIN axonemal central pair apparatus protein-like) as a master SD gene in channel catfish. Hydin is located within the sex determination region (SDR) within a mapped 8.9-Mb non-recombinational segment on chromosome 4 of channel catfish. It is highly expressed in genetic males, but not in genetic females. The alleles of X and Y are highly differentially methylated with the X chromosome being hypermethylated and the Y chromosome hypomethylated. The hypomethylated Y allele of hydin is expressed while the hypermethylated X allele is not expressed. Such allelic expression fits well with the XY sex determination system of channel catfish. Functional analysis using a methylation blocker, 5-aza-dC, demonstrated that demethylation, especially within the SDR, is accompanied with increased expression of hydin, which led to sex reversal of genetic females into phenotypic males. These evidences support the candidacy of hydin as a master SD gene in channel catfish. Future knockout and analysis of affected genes after hydin knockout should provide insights into how hydin functions as a master SD gene.

Northern Crayfish, Faxonius virilis, displays various strategies that allow them to survive extended periods of oxygen deprivation. However, certain epigenetic adaptations that these crayfish use have not been studied in detail, and the role of specific mechanisms used such as histone modifications remain unknown. Epigenetic studies offer a new perspective on how crayfish can regulate gene expression to redirect energy to essential functions needed for survival. This study investigates the regulation of histone modifications of proteins including acetylation and deacetylation in F. virilis in response to 20-h anoxia exposure. These histone modifications were studied via analysis of writer, reader, and eraser proteins such as lysine acetyltransferases (KATs), bromodomain proteins (BRDs), histone deacetylases (HDAC), and sirtuin proteins (SIRTs). Significant upregulation was seen in one histone protein and one lysine acetyltransferase: H3K14Ac and KAT2A. These proteins are known to be regulated by BRD2; a protein that specifically reads and targets H3K14Ac. In response to anoxia, a larger number of histone deacetylases and sirtuin proteins were upregulated in comparison to lysine acetyltransferases suggesting a focus on suppression of gene expression. The histone deacetylases and sirtuin proteins with significant upregulation were HDAC2, HDAC3, SIRT2, SIRT3, and SIRT6. These proteins have also all been implicated in DNA damage regulation which further suggests that crayfish focus limited energy on ensuring cell survival. This study provides an understanding of how histone acetylation and deacetylation are regulated in crayfish as a component of metabolic rate suppression under anoxia.

Saprolegniasis caused by Saprolegnia parasitica leads to significant economic losses in the aquaculture industry worldwide. Effector proteins secreted by pathogens are key molecules involved in their pathogenicity and long non-coding lncRNAs (lncRNAs) act as regulators in these processes. However, little is known about the lncRNAs and effector proteins in S. parasitica. Here, we first identified 1027 lncRNAs during the developmental stages and infection process of S. parasitica. Compared with mRNAs, these lncRNAs had shorter sequences and exon lengths and lower expression levels. In addition, their sequence conservation among other oomycete species was also low. The S. parasitica lncRNAs were characterized according to developmental stage and infection time point. We also identified effector proteins using a computational pipeline. In total, 131 S. parasitica effector proteins were identified and classified into 34 families. The 47 genes encoding effector genes were neighbors of 39 lncRNAs, and there was a correlation between the transcription level of lncRNAs and their neighboring genes. Gain- and loss-of-function experiments revealed that lncRNA8375.2 promoted the expression of a neighboring effector gene, SpCAP. Our results provide new data on S. parasitica lncRNAs and effector proteins, and provide insights into the lncRNA-effector module involved in S. parasitica.

Edwardsiella anguillarum and Aeromonas hydrophila are two common bacterial pathogens affecting cultivated eels, and the differences in their virulence remain unclear. In this study, after two groups of American eels (Anguilla rostrata) were administered the LD₅₀ dose of E. anguillarum and A. hydrophila, respectively, the histopathology of the liver, trunk kidney, and spleen, as well as transcriptomic RNA sequencing (RNA-seq) analysis of the spleen, was examined at three time points: pre-infection (Con group) and post-infection at 36 h (Ea_36 group, Ah_36 group) and 60 h (Ea_60 group, Ah_60 group). The results showed that the differences in pathological changes were characterized by severe hepatocyte edema at 36 h post-infection (hpi) and hepatocyte atrophy at 60 hpi in the livers of eels infected by A. hydrophila, in contrast to the severe atrophy of glomeruli in the trunk kidneys and numerous bacterial nodules in the spleens of eels infected by E. anguillarum. The RNA-seq results revealed 906 and 77 typical differentially expressed genes (DEGs) in eels infected with E. anguillarum and A. hydrophila, respectively, compared to the control eels. The DEGs between the infected and control groups were predominantly annotated in GO terms related to binding, catalytic activity, membrane part, cell part, and cellular process, as well as in KEGG pathways associated with human diseases and organismal systems. The GO enrichment analysis showed 83 and 146 differential GO terms, along with 32 and 78 differential KEGG pathways in two comparisons of Ea_36 vs Con versus Ah_36 vs Con and Ea_60 vs Con versus Ah_60 vs Con, respectively. Furthermore, the analysis of differential alternative splicing genes (DASs) showed 1244 and 1341 DASs out of 12,907 and 12,833 AS genes, respectively, in the comparisons of Ea_36 vs Ah_36 and Ea_60 vs Ah_60. These DASs were enriched in two common KEGG pathways: “NOD-like receptor signaling pathway” and “necroptosis” which shared 11 hub DASs. Finally, analysis of protein–protein interactions revealed that 91 of 412 cross DASs between Ea_36 vs Ah_36 and Ea_60 vs Ah_60 potentially play an essential role in the difference in virulence of E. anguillarum and A. hydrophila in American eels, with 12 encoded proteins being particularly notable. Together, this study is the first to report a comparative pathogenicity and RNA-seq analysis of E. anguillarum and A. hydrophila in American eels, shedding new light on our understanding of the differences in virulence as revealed by pathological changes, DEGs, and DASs, contributing to more effective control strategies to prevent outbreaks of bacterial infections.

The issue of heavy metal pollution in aquaculture ponds is becoming increasingly severe, posing a significant threat to the healthy development of the aquaculture industry. Heavy metals such as cadmium and copper accumulate in ponds, not only exerting toxic effects on aquatic organisms and affecting their growth and reproduction but also endangering human health through the food chain. Bioremediation, as a green and environmentally friendly technology, utilizes specific organisms to absorb, transform, and immobilize heavy metals. We examined metal accumulation, traditional metal-related biomarkers, alongside transcriptomic and tissue histological analyses, in the hepatopancreas of Corbicula fluminea following a 14-day exposure to copper (20 µg/L), cadmium (20 µg/L), or combined copper-cadmium treatments (20 µg/L Cu and 20 µg/L Cd). Metal exposure led to notable metal accumulation in the clam’s hepatopancreas. Analysis of traditional biomarkers revealed signs of cellular injury and oxidative stress in clams post-metal exposure. Transcriptomic analysis across the three treatment groups revealed disruptions in immune response, response to metal ion, and energy metabolism, characterized by differential expression levels of key genes such as ABCA3, MYD88, TOLLIP, TBK1, C2, C4, c-Myc, SYK, and SAMHD1. These findings deepen our understanding of the adverse effects of metal exposure on freshwater organisms and evaluate the potential of Corbicula fluminea for removing heavy metals from aquaculture ponds.

The present work investigated the effects of embryonic temperature on the responses of Atlantic salmon (Salmo salar) alevins to a bacterial challenge using Yersinia ruckeri as a model pathogen. Embryos were reared at 4 °C, 6 °C, and 8 °C from fertilization to the eyed-egg stage. Alevins, before the start of feeding, were challenged with the pathogen, and mortality and early immune responses in mucosal organs were assessed. Fish from the 4 °C and 6 °C groups exhibited higher survival probabilities than those from the 8 °C group 72 h post-infection. Mild histopathological changes were observed in the gills and skin across all temperature groups, with bacterial antigen detected in the secondary lamellae of gills and in the skin epithelial and basal layers. Gene expression profiling revealed slightly distinct immune gene expression patterns in low-temperature groups (4 °C and 6 °C) compared to the 8 °C group. Gelsolin (gsn) expression increased in the skin across all temperature groups at 72 h post-infection. Claudin (cldn4) and collagen (col1a) were only upregulated in the skin of the 4 °C group, while heat shock protein 70 (hspa1a) was downregulated in the gills of infected fish at 72 h compared to controls. Toll-like receptor 13 (tlr13) expression increased in infected fish at 24 h compared to controls. In the 6 °C and 8 °C groups, gsn expression also increased at 72 h post-infection. Cldn4 expression increased only in the gills of 8 °C infected fish. This study revealed that low embryonic temperature could influence survival and mucosal immune defences following a bacterial challenge in Atlantic salmon alevins.

The spotted sea bass (Lateolabrax maculatus), a eurythermal species, exhibits strong adaptability to temperature variations and presents an ideal model for studying heat stress-responsive mechanisms in fish. This study examined the liver transcriptome of spotted sea bass over a 24-h period following exposure to elevated temperatures, rising from 25 to 32 °C. The results revealed significant alterations in gene expression in response to this thermal stress. Specifically, we identified 1702, 1199, 3128, and 2636 differentially expressed genes at 3, 6, 12, and 24 h post-stress, respectively. Weighted Gene Co-expression Network Analysis (WGCNA) was used to identify specific gene modules responsive to heat stress, containing hub genes such as aco2, eci2, h6pd, suclg1, fgg, fga, fgb, f2, and apoba, which play central roles in the heat stress response. Enrichment analyses via KEGG and GSEA indicated that upregulated differentially expressed genes (DEGs) are predominantly involved in protein processing in the endoplasmic reticulum, while downregulated genes are primarily associated with the AGE-RAGE signaling pathways. Additionally, 272 genes exhibited differential alternative splicing, primarily through exon skipping, underscoring the complexity of transcriptomic adaptations. These findings provide deeper insights into the molecular responses to thermal stress and are crucial for advancing the breeding of heat-resistant strains of spotted sea bass.

The Atlantic coastline of El-Jadida, Morocco, is renowned for its plentiful algae, especially brown seaweed, which is rich in active compounds known for their antifungal properties. This valuable resource offers an exciting opportunity to tackle the numerous challenges posed by invasive fungal infections, allergies, mycotoxin-related food poisoning, and drug-resistant strains. Underscoring the urgent need to explore alternative, sustainable, and environmentally friendly antifungal agents derived from algae. This study aimed to evaluate the antifungal activity of total alkaloids and phenolic-rich fractions derived from seven species of Pheophyceae: Sargassum muticum, Sargassum vulgare, Bifurcaria bifurcata, Cystoseira tamariscifolia, Cystoseira humilis, Laminaria ochroleuca, and Fucus spiralis against four fungi: airborne toxigenic isolates of Aspergillus westerdijkiae and Chaetomium globosum as well as nosocomial opportunistic isolates of Aspergillus nidulans and Scopulariopsis brevicaulis. The study also aimed to identify the most effective alga and its specific active compounds through LC–MS and GC–MS analysis. The invasive Sargassum muticum was chosen as the most potent alga in inhibiting the growth of mycelium. For the first time, the alkaloids palmatine and jatrorrhizine, along with caulerpin, have been identified. The chloroform fraction revealed the prevalence of phenolic compounds including, phenolic acids, flavonoids, and phlorotannins. The lowest minimum inhibitory concentrations (MICs), with a maximum fungal load of 10⁸ colony-forming unit (CFU), recorded ranged from 3.12 to 6.25 μg/mL by the phenolic-rich fraction against airborne toxigenic isolates, and from 100 to 200 μg/mL against nosocomial opportunistic isolates by the total alkaloids. In comparison, the positive control, ketoconazole, showed higher MICs and resistance against A. nidulans. The valorization of Sargassum muticum is proposed as a green strategy to preserve the ecological balance, combat antifungal resistance, and address public health challenges.

Graphical Abstract

Pufferfish of the genus Takifugu possess tetrodotoxin (TTX), known as “pufferfish toxin” and it is believed that pufferfish eggs and newly hatched larvae utilize TTX as a defensive substance against predators. However, the mechanism for the placement of TTX to specific cells on the larval body surface during the developmental process remains unknown. In this study, we clarify the distribution and characteristics of TTX-rich cells. We performed whole-mount immunohistochemistry (IHC) using anti-TTX monoclonal antibody on larvae of two pufferfish species, Takifugu rubripes and Takifugu alboplumbeus, just after hatching. This allowed observation of the TTX location and compared it with those of wheat germ agglutinin (WGA)-positive (periodic acid-Schiff (PAS)-positive) cells for mucous cells and IHC using anti-Na⁺/K⁺-ATPase (NKA) monoclonal antibody for ionocytes. As a result, uniformly scattered localization of TTX-rich cells was commonly observed in the epidermis of the larvae of the two Takifugu species. TTX-rich cells were WGA-negative (PAS-negative) and structurally distinct from NKA-positive cells, suggesting that TTX-rich cells are unreported small cells unique to pufferfish skin, but not mucous cells nor ionocytes.