RESUMEN
Intensive aquaculture of grass carp often leads to decreased immunity and increased disease prevalence, resulting in economic losses. Improving grass carp immunity is therefore a critical strategy for addressing these challenges. Akirin reportedly participates in myogenesis, growth, and immune responses. However, its role in grass carp remains unclear. Herein, we isolated akirins from the spleen of grass carp and analyzed their tissue-specific expression. Akirin expression was detected following treatment with poly (I:C), LPS, and Aeromonas hydrophila (A. hydrophila). The immunological function of the akirin protein was evaluated in head kidney leukocytes (HKLs). The results revealed that the coding sequence (CDS) of akirin1 is 570 bp, encoding 189 amino acids. There was one predicted nuclear localization signal (NLS) and two predicted α- helix domains. The CDS of akirin2 is 558 bp, encoding 185 amino acids. There were two predicted NLSs and two predicted α-helix domains. Tissue-specific expression analysis showed that akirins are widely detected in grass carp tissues. akirin1 was highly detected in the brain, kidneys, heart, spleen, and gonads, while akirin2 was highly detected in the brain, liver, gonads, kidneys, spleen, and heart. The mRNA levels of akirins were promoted after treatment with poly (I:C), LPS, and A. hydrophila. Recombinant akirin proteins were produced in Escherichia coli (E. coli). il-1ß, ifnγ, il-6, tnfα, il-4, iκbα, and nfκb were markedly increased in grass carp HKLs by treatment with the akirin protein. These results suggest that akirins play a role in the immunological regulation of grass carp.
RESUMEN
Aeromonas hydrophila is one of the most prevalent pathogenic bacteria in largemouth bass. The use of antibiotics to inhibit A. hydrophila poses a significant threat to fish and environmental safety. Bacillus velezensis, a safe bacterium with probiotic and antibacterial characteristics, is an ideal candidate for antagonizing A. hydrophila. This study explored the antagonistic effects of B. velezensis FLU-1 on A. hydrophila in vivo and in vitro. In addition, we explored the antimicrobial peptides (AMPs) produced by strain FLU-1 and clarified the underlying antibacterial mechanisms. The results showed that strain FLU-1 could inhibit a variety of fish pathogens, including A. hydrophila. The challenge test showed that dietary supplementation with B. velezensis FLU-1 significantly improved the survival rate of largemouth bass and reduced the bacterial load in liver. Subsequently, the AMP LCI was isolated from B. velezensis FLU-1 and was found to be effective against A. hydrophila in vitro and in vivo. Transcriptomic analysis revealed that LCI downregulated the genes associated with flagellar assembly and peptidoglycan synthesis in A. hydrophila. Phenotypic test results showed that LCI disrupted the membrane integrity, markedly reduced the biofilm biomass and diminished the swimming motility of A. hydrophila. Furthermore, the results showed that LCI bound to the genomic DNA of A. hydrophila and destroyed the DNA structures. Overall, these findings elucidated the mechanism of action of LCI against A. hydrophila at the phenotypic and physiological levels. This study suggests that B. velezensis FLU-1 and its AMP LCI could serve as antibiotic alternatives for controlling pathogens in aquaculture.
RESUMEN
The effects of antipsychotic drugs on aquatic organisms have received widespread attention owing to their widespread use and continued release in aquatic environments. The toxicological effects of antipsychotics on aquatic organisms, particularly fish, are unexplored, and the underlying mechanisms remain unelucidated. This study aimed to use common carp to explore the effects of antipsychotics (olanzapine [OLA] and risperidone [RIS]) on behavior and the potential mechanisms driving these effects. The fish were exposed to OLA (0.1 and 10 µg/L) and RIS (0.03 and 3 µg/L) for 60 days. Behavioral tests and neurological indicators showed that exposure to antipsychotics could cause behavioral abnormalities and neurotoxicity in common carp. Further, 16 S rRNA sequencing revealed gut microbiota alteration and decreased relative abundance of some strains related to SCFA production after OLA and RIS exposure. Subsequently, a pseudo-sterile common carp model was successfully constructed, and transplantation of the gut microbiota from antipsychotic-exposed fish caused behavioral abnormalities and neurotoxicity in pseudo-sterile fish. Further, SCFA supplementation demonstrated that SCFAs ameliorated the behavioral abnormalities and neurological damage caused by antipsychotic exposure. To our knowledge, the present study is the first to investigate the effects of antipsychotics on various complex behaviors (swimming performance and social behavior) in common carp, highlighting the potential health risks associated with antipsychotic drug-induced neurotoxicity in fish. Although these results do not fully elucidate the mechanisms underlying the effects of antipsychotic drugs on fish behavior, they serve as a valuable initial investigation and form the basis for future research.