Background
Our previous study revealed that feeding the antimicrobial peptide (AMP) product Scy-hepc significantly enhances the growth of mariculture fish through the activation of the GH-Jak2-STAT5-IGF1 axis. However, the contribution of gut microbiota to this growth enhancement remains unclear. This study aimed to elucidate the potential mechanism involved in intestinal absorption and modulation of gut microbiota in
Epinephelus akaara
following Scy-hepc feeding.
Results
The results showed that a 35 day regimen of Scy-hpec markedly promoted the growth of
E. akaara
compared to groups supplemented with either florfenicol,
B. subtilis
, or a vector. The growth enhancement is likely attributed to alterations in microbiota colonization in the foregut and midgut, characterized by an increasing abundance of potential probiotics (
Rhizobiaceae
and
Lysobacter
) and a decreased abundance of opportunistic pathogens (
Psychrobacter
and
Brevundimonas
) as determined by
16S rRNA
analysis. Additionally, similar to the effect of florfenicol feeding, Scy-hepc significantly improved host survival rate by over 20% in response to a lethal dose challenge with
Edwardsiella tarda
. Further investigations demonstrated that Scy-hepc is absorbed by the fish foregut (20–40 min) and midgut (20–30 min) as confirmed by Western blot, ELISA, and Immunofluorescence. The absorption of Scy-hepc affected the swimming, swarming and surfing motility of
Vibrio harveyi
and
Bacillus thuringiensis
isolated from
E. akaara
’s gut. Moreover, Scy-hepc induced the downregulation of 40 assembly genes and the upregulation expression of 5, with the most significant divergence in gene expression between opportunistic pathogens and probiotics concentrated in their motility genes (
PomA/B, MotA
/
B
).
Conclusions
In summary, this study shows that feeding AMP Scy-hepc can promote growth and bolster immunity in
E. akaara
. These beneficial effects are likely due to the absorption of Scy-hepc in the fish’s foregut and midgut, which modulates the colonization and motility of commensal bacteria, leading to favorable changes in the composition of the foregut and midgut microbiota. Therefore, a profound understanding of the mechanisms by which antimicrobial peptides affect host gut microbiota will contribute to a comprehensive assessment of their advantages and potential application prospects as substitutes for antibiotics in fish health and improving aquaculture practices.
Supplementary Information
The online version contains supplementary material available at 10.1186/...
