Rainbow trout is a highly valued freshwater fish species known for its delicious taste and economic importance. However, trout aquaculture faces challenges such as maintaining water quality, preventing diseases, and ensuring the optimal health of the fish.
A promising approach to addressing these challenges is the use of probiotics. Probiotics are live microorganisms that provide health benefits to the host organism. In rainbow trout aquaculture, probiotics are added to the fish’s feed or water to improve gut health, stimulate the immune system, and enhance growth performance.
A recent study published in Scientific Reports by scientists from the Nuclear Science and Technology Research Institute (Iran) explored the potential of a probiotic strain, Bacillus subtilis MS. 45, to improve the growth, immunity, and stress resistance of rainbow trout (Oncorhynchus mykiss).
Bacillus subtilis: A Friend to Fish
Bacillus subtilis is a natural bacterium commonly found in soil and the digestive tract of animals, including fish. Some strains of Bacillus subtilis have been identified as probiotics, meaning they offer health benefits to their host. In the context of aquaculture, Bacillus subtilis probiotics can:
- Promote gut health: A healthy gut microbiome is essential for proper digestion and nutrient absorption in fish. Bacillus subtilis can help establish a balanced gut microbiota, leading to better intestinal health and overall well-being of the fish.
- Stimulate the immune system: Bacillus subtilis can stimulate the immune system of rainbow trout, making them more resistant to infections and diseases. This can improve fish survival rates and reduce the reliance on antibiotics in aquaculture.
- Improve growth performance: Studies have shown that rainbow trout fed diets supplemented with Bacillus subtilis exhibit better growth rates and feed conversion ratios. This translates into greater production efficiency and profitability for fish farmers.
Optimizing Bacillus subtilis Through Mutation
While Bacillus subtilis offers numerous benefits for rainbow trout aquaculture, researchers are constantly striving to enhance its efficacy. One approach involves creating mutant strains of Bacillus subtilis with improved probiotic properties. Mutation can be induced through various methods, such as exposure to ultraviolet or gamma radiation. These mutant strains may exhibit:
- Increased production of antimicrobial compounds: Certain strains of Bacillus subtilis can produce natural antibiotics that combat harmful bacteria in the fish’s gut. Mutation may potentially increase the production of these beneficial compounds, further enhancing the probiotic’s ability to control pathogens.
- Improved stress tolerance: Aquaculture environments can expose fish to various stressors, such as low oxygen levels (hypoxia). Mutant strains of Bacillus subtilis may be better equipped to help fish cope with these stressors, promoting overall health and resilience.
The Study: How Bacillus subtilis MS. 45 Benefits Rainbow Trout
The researchers investigated the effects of Bacillus subtilis MS. 45 on rainbow trout exposed to low oxygen stress (hypoxia). Low oxygen levels are a common challenge in aquaculture ponds and can negatively impact fish health.
The results were promising! Rainbow trout fed with Bacillus subtilis MS. 45 showed:
- Improved growth performance
- Enhanced immune function, including increased activity of immune cells and genes
- Reduced stress markers
- Better overall survival under hypoxic stress
Implications for Rainbow Trout Aquaculture
These findings suggest that Bacillus subtilis MS. 45 has the potential to be a valuable tool for rainbow trout aquaculture. By promoting gut health, immunity, and stress tolerance, this probiotic could contribute to:
- Healthier fish populations
- Reduced dependence on antibiotics in aquaculture
- More sustainable aquaculture practices
Conclusion
“In the present study, the generation of the mutant strain B. subtilis MS. 45 through gamma irradiation increased the antagonistic activity against important pathogenic bacteria in aquaculture, Aeromonas hydrophila and Pseudomonas fluorescens, as well as growth and biomass production under in vitro conditions,” the scientists conclude.
Further research is needed to optimize the use of Bacillus subtilis MS. 45 in aquaculture settings. However, this study highlights the exciting possibilities of probiotics for enhancing fish health and promoting sustainable aquaculture.
The study was funded by the Nuclear Science and Technology Research Institute (Iran).
Contact
Alireza Neissi
Nuclear Agriculture Research School, Nuclear Science and Technology Research Institute
Karaj, 31465-1498, Iran
Email: aneissi@aeoi.org.ir
Reference (open access)
Neissi, A., Majidi Zahed, H. & Roshan, R. Probiotic performance of B. subtilis MS. 45 improves aquaculture of rainbow trout Oncorhynchus mykiss during acute hypoxia stress. Sci Rep 14, 3720 (2024). https://doi.org/10.1038/s41598-024-54380-7
