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The growth environment significantly influences the intestinal microbiota of aquatic organisms. We investigated the composition and functional differences in the intestinal microbiota of red claw crayfish (Cherax quadricarinatus) in rice fields (RB) and ponds (PB) by 16S rDNA high-throughput sequencing technology. The results indicate that the Shannon, Simpson, Sobs, Chao1, and ACE indices of PB are all higher than those of RB, demonstrating greater diversity and richness of intestinal microbiota. The dominant phyla in the intestinal microbiota of the Cherax quadricarinatus were Proteobacteria, Tenericutes, and Firmicutes. Tenericutes and Proteobacteria were significantly more abundant in the RB than in the PB, while Planctomycetes and Firmicutes were significantly more abundant in the PB than in the RB. The results of network correlation analysis indicate that Proteobacteria and Firmicutes exhibit strong connectivity with other microbial groups in the gut microbiota of Cherax quadricarinatus, showing significant centrality. They play an important role in the interactions within the gut microbiota community. The dominant bacterial genera in the Cherax quadricarinatus’s gut were Citrobacter, Candidatus_Bacilloplasma, and Clostridium_sensu_stricto_1. The abundance of the genus Clostridium was significantly higher in the PB than in the RB, whereas the abundance of Candidatus_Hepatoplasma and Vibrio was significantly lower in the PB than in the RB. The prediction function of KEGG enrichment showed that the abundance of Amino acid metabolism, Biosynthesis of Other Secondary Metabolites, Transport and Catabolism, Cancers, and Nervous System, Substance Dependence were significantly higher in the PB, while the infectious diseases pathway was enriched in the RB. In summary, our results revealed significant differences in the composition and diversity of intestinal microbiota in the Cherax quadricarinatus between rice paddy and pond farming environments. The intestinal microbiota of the Cherax quadricarinatus grown in pond environments exhibit higher diversity and stability, manifested by an increase in beneficial bacteria abundance and a decrease in opportunistic pathogens. These findings significantly improve understanding of the complex relationship among Cherax quadricarinatus, intestinal microbiota, and the environment.

Skin microbiota play an important role in skin barrier function and are associated with host health. The study of the skin microbiota is beneficial for managing disease with skin microbiota. Bullfrog (Rana catesbeiana) is an important cultured animal. Bacterial diseases like red leg syndrome (RLS) often occur in bullfrog cultured and cause huge economic losses around the world. However, the appearance of RLS is unknown. Here we compare the skin microbiota of RLS bullfrog and healthy bullfrog by 16 S rRNA microbiome profiles. The bacterial community diversity of bullfrog skin was significantly different between RLS and healthy group. Proteobacteria, Bacteroidota, Firmicutes were the most abundant phyla in bullfrog skin. Compared with healthy bullfrogs, RLS bullfrogs had high abundance of Acinetobacter, Chryseobacterium, Elizabethkingia, Flavobacterium and Streptococcus in skin microbiota, but the relative abundance of Cetobacterium, Bacteroides and Shewanella was overrepresented in the RLS bullfrog. The Tax4Fun function prediction showed that the relative abundance of genes associated with Nucleotide metabolism, Translation, Nucleotide metabolism, Translation, Glycan biosynthesis and metabolism exhibited was significantly higher in RLS bullfrogs. The results suggested that the RLS significantly changed the composition and predictive function of the skin bacterial community in cultured bullfrogs. This study is the first to report on the relationship between skin microbiota and red leg syndrome of bullfrog, which can expand our understanding of bacterial communities in bullfrog farming from the perspective of microbial ecology and help prevent and manage RLS in bullfrog farming.

Singapore grouper iridovirus (SGIV) is a virus with high fatality rate in the grouper culture industry. The outbreak of SGIV is often accompanied by a large number of grouper deaths, which has a great impact on the economy. Therefore, it is of great significance to find effective drugs against SGIV. It has been reported that edaravone is a broad-spectrum antiviral drug, most widely used clinically in recent years, but no report has been found exploring the effect of edaravone on SGIV infections. In this study, we evaluated the antiviral effect of edaravone against SGIV, and the anti-SGIV mechanism of edaravone was also explored. It was found that the safe concentration of edaravone on grouper spleen (GS) cells was 50 µg/mL, and it possessed antiviral activity against SGIV infection in a dose-dependent manner. Furthermore, edaravone could significantly disrupt SGIV particles and interference with SGIV binding to host cells, as well as SGIV replication in host cells. However, edaravone was not effective during the SGIV invasion into host cells. This study was the first time that it was determined that edaravone could exert antiviral effects in response to SGIV infection by directly interfering with the processes of SGIV infecting cells, aiming to provide a theoretical basis for the control of grouper virus disease.

IntroductionThe bacterium Elizabethkingia miricola is a multispecies pathogen associated with meningitis-like disease that has been isolated from several amphibian species, including the bullfrog, but this is the first isolation in Guangxi. In the present study, the dominant bacteria were isolated from the brains of five bullfrogs with meningitis-like disease on a South China farm in Guangxi.MethodsThe NFEM01 isolate was identified by Gram staining; morphological observations; 16S rRNA, rpoB, and mutT-based phylogenetic tree analysis; and physiochemical characterization and was subjected to drug sensitivity and artificial infection testing.Results and discussionAs a result of identification, the NFEM01 strain was found to be E. miricola. An artificial infection experiment revealed that NFEM01 infected bullfrogs and could cause symptoms of typical meningitis-like disease. As a result of the bacterial drug sensitivity test, NFEM01 is highly sensitive to mequindox, rifampicin, enrofloxacin, nitrofural, and oxytetracycline and there was strong resistance to gentamicin, florfenicol, neomycin, penicillin, amoxicillin, doxycycline, and sulfamonomethoxine. This study provides a reference to further study the pathogenesis mechanism of E. miricola-induced bullfrog meningitislike disease and its prevention and treatment.

(1) Background: Largemouth bass virus (LMBV) is a major viral pathogen in largemouth bass (Micropterus salmoides) aquaculture that often causes high mortality and heavy economic losses, thus developing treatments to combat this pathogen is of great commercial importance. Green tea is a well-known medicinal plant that contains active ingredients with antiviral, antibacterial, and other biological activities. The goals of this study were to explore the effect and mechanism of green tea source compounds on LMBV and provide data to serve as the basis for the screening of targeted drugs in the future. In this study, we evaluated the effects of the main component of green tea, epigallocatechin-3-gallate (EGCG), against LMBV infection. (2) Methods: The safe working concentration of EGCG was identified by cell viability detection and light microscopy. The antiviral activity and mechanism of action of EGCG against LMBV infection were evaluated with light microscopy, an aptamer 6-carboxy-fluorescein-based fluorescent molecular probe, and reverse transcription quantitative PCR. (3) Results: The safe working concentration of EGCG was ≤10 μg/mL. EGCG showed significant anti-LMBV infection activity in a concentration-dependent manner, and it also destroyed the structure of virus particles. EGCG impacted the binding of virus particles to cell receptors and virus invasion into the host cells. Inhibitory effects of EGCG on LMBV particles, LMBV binding to the host-cell membrane, and LMBV invasion were 84.89%, 98.99%, and 95.23%, respectively. Meanwhile, the effects of EGCG subsequently were verified in vivo. The fatality rate of the LMBV + EGCG group was significantly lower than that of the LMBV group. (4) Conclusions: Our results suggest that EGCG has effective antiviral properties against LMBV and may be a candidate for the effective treatment and control of LMBV infections in largemouth bass aquaculture.

The title compound, C16H12O2, contains two prop-2-yn-1-yloxy groups attached to a naphthalene ring system at the 1- and 6-positions. The crystal packing includes an intermolecular C—H...π interaction between a terminal ethynyl H atom and an ethynyl group on a glide-related molecule and another interaction between an O-atom-linked methylene H and an ethynyl group of a different glide-related molecule.