Gut–Liver Immune Response and Gut Microbiota Profiling Reveal the Pathogenic Mechanisms of Vibrio harveyi in Pearl Gentian Grouper (Epinephelus lanceolatus♂ × E. fuscoguttatus♀)

Abstract

Vibrio harveyi causes vibriosis in nearly 70% of grouper (Epinephelus sp.), seriously limiting grouper culture. As well as directly inhibiting pathogens, the gut microbiota plays critical roles in immune homeostasis and provides essential health benefits to its host. However, there is still little information about the variations in the immune response to V. harveyi infection and the gut microbiota of grouper. To understand the virulence mechanism of V. harveyi in the pearl gentian grouper, we investigated the variations in the pathological changes, immune responses, and gut bacterial communities of pearl gentian grouper after exposure to differently virulent V. harveyi strains. Obvious histopathological changes were detected in heart, kidney, and liver. In particular, nodules appeared and huge numbers of V. harveyi cells colonized the liver at 12 h postinfection (hpi) with highly virulent V. harveyi. Although no V. harveyi was detected in the gut, the infection simultaneously induced a gut-liver immune response. In particular, the expression of 8 genes associated with cellular immune processes, including genes encoding inflammatory cytokines and receptors, and pattern recognition proteins, was markedly induced by V. harveyi infection, especially with the highly virulent V. harveyi strain. V. harveyi infection also induced significant changes in gut bacterial community, in which Vibrio and Photobacterium increased but Bradyrhizobium, Lactobacillus, Blautia, and Faecalibaculum decreased in the group infected with the highly virulent strain, with accounting for 82.01% dissimilarity. Correspondingly, four bacterial functions related to bacterial pathogenesis were increased by infection with highly virulent V. harveyi, whereas functions involving metabolism and genetic information processing were reduced. These findings indicate that V. harveyi colonizes the liver and induces a gut-liver immune response that substantially disrupts the composition of and interspecies interactions in the bacterial community in fish gut, thereby altering the gut-microbiota-mediated functions and inducing fish death.

Sinomenine Hydrochloride Ameliorates Fish Foodborne Enteritis via α7nAchR-Mediated Anti-Inflammatory Effect Whilst Altering Microbiota Composition

“…The sampling of 16S sequencing analysis followed the method published in previous studies by Deng et al. ( 44 ). For the sampling of larvae, only 27 dpf larvae (n = 6) were sampled for HE staining at the meantime of imaging the adaptive immune cells.…”

“…For all omics studies, the hindgut from one female and one male adult zebrafish were mixed for each sample (three repetitions) to avoid sex-biased differences for both transcriptome and 16S. The sampling of 16S sequencing analysis followed the method published in previous studies by Deng et al (44). For the sampling of larvae, only 27 dpf larvae (n = 6) were sampled for HE staining at the meantime of imaging the adaptive immune cells.…”

Dietary Inclusion of Seabuckthorn (Hippophae rhamnoides) Mitigates Foodborne Enteritis in Zebrafish Through the Gut-Liver Immune Axis

“…Additionally, as a result of the interaction between the gut microbiota and the liver ( Deng et al, 2020 ), our findings indicated that seabuckthorn supplementation resulted in an increase in OTU numbers and an FM-biased bacterial community in the SB group compared to the SBM group. Taxonomic changes were observed at the phylum level, as Actinobacteria were found to produce active metabolites against pathogenic microorganisms ( Jami et al, 2015 ), and the current study revealed an increase in Actinobacteria, suggesting a protective role for the SB group.…”

“…We used the hindgut tissue from both female and male fish for the omics investigation to prevent sex-biased differences. The complete hindgut contents were collected in sterile tubes and preserved at −80°C for 16S rRNA gene sequencing ( Deng et al, 2020 ). For the sampling of larvae, only the caudal part of 27 dpf larvae has been sampled for HE (Hematoxylin–eosin) staining, during the imaging of the adaptive immune cells.…”

Gene Expression Profile and Co-Expression Network of Pearl Gentian Grouper under Cold Stress by Integrating Illumina and PacBio Sequences

“…Therefore, whether it can adapt to low temperature directly affects the survival, feeding, and growth of Pearl gentian group. Nevertheless, previous studies mainly focused on feed nutrition and pathology [24][25][26][27] and did not involve research on gene expression related to low temperature. Besides, the molecular regulation mechanism underlying cold stress in pearl gentian grouper species remains largely unidentified.…”