In the world of aquaculture, where the balance between productivity and sustainability is a constant tightrope walk, a recent study has shed light on a promising avenue for enhancing fish health and growth. Researchers, led by Wenhao Ren from the School of Marine Science and Engineering at Qingdao Agricultural University in China, have uncovered the potential of a probiotic bacterium, Enterococcus thailandicus HR23, to boost the growth and immune response of rainbow trout. The findings, published in the journal Aquaculture Reports (translated as Aquaculture Reports), could have significant implications for the aquaculture industry, particularly in managing fish health and improving production efficiency.
The study focused on the bacteriocins produced by E. thailandicus HR23, which are peptide-like substances known for their ability to inhibit pathogenic microbes. “Many probiotics are capable of secreting bacteriocins to inhibit pathogenic microbes,” Ren explained. “However, the probiotic mechanisms of bacteriocin-producing bacteria in aquatic animals remain poorly understood.” This research aimed to bridge that gap, exploring the role of HR23 in both in vitro and in vivo settings.
In vitro experiments revealed that HR23 produces a peptide-like bactericidal component that can disrupt the cell membrane of Aeromonas salmonicida, a pathogen known to cause significant losses in aquaculture. Whole-genome sequencing of HR23 showed that it encodes a variety of genes associated with stress tolerance and the synthesis of cyclic bacteriocin, enterocin NKR-5–3B. This genetic makeup suggests that HR23 is well-equipped to survive harsh conditions and produce potent antimicrobial substances.
The in vivo experiments, conducted on rainbow trout, demonstrated that HR23 significantly improved growth performance and resistance to A. salmonicida infection. The supplementation of HR23 led to notable changes in the intestinal microbiota of the fish. After 14 days, there was a significant decrease in diversity, followed by an increase in community richness after 21 days. At the phylum level, there was an increase in the abundance of Firmicutes and Bacteroidota, while Proteobacteria and Verrucomicrobiota decreased. Beneficial bacteria such as Bifidobacterium breve, Bacillus, and Lactobacillus saw an increase, while potential harmful bacteria like Streptococcus, Desulfovibrio, Staphylococcus, Escherichia coli, and Archangium gephyra decreased.
The study also found that HR23 supplementation activated immune pathways such as THαβ and TH1, while reducing the expression level of the inflammation-related gene IL-1β. This suggests that HR23 not only enhances the growth performance of rainbow trout but also bolsters their immune response, making them more resilient to infections.
The implications of this research for the aquaculture industry are substantial. By leveraging the beneficial effects of bacteriocin-producing probiotics like HR23, farmers can potentially reduce their reliance on antibiotics, which are often used to control infections but can lead to antibiotic resistance and other environmental issues. “This study provided insights into the mechanisms of bacteriocin-producing bacteria and further explored beneficial microbial bacteriocin metabolites to support healthy aquaculture,” Ren noted.
The findings also open up new avenues for research into the gut microbiota of aquatic animals and how it can be manipulated to improve health and productivity. As the aquaculture industry continues to grow, the need for sustainable and effective health management strategies becomes ever more critical. This research offers a promising step in that direction, providing a glimpse into the future of aquaculture where probiotics and bacteriocins play a central role in maintaining fish health and enhancing production efficiency.
In the broader context, this study highlights the importance of understanding the complex interactions between microbes and their hosts. As we delve deeper into the microbial world, we uncover more about the intricate web of life and the potential it holds for improving our own health and the health of the animals we rely on for food. The journey is just beginning, and the discoveries made by researchers like Wenhao Ren and his team are paving the way for a more sustainable and productive future in aquaculture.