Aquaculture is the fastest-growing food production sector. However, it faces significant challenges, including demand from a growing global population, which is estimated to reach 10.4 billion by the year 2100, disease outbreaks, environmental impacts, and the overuse of antibiotics. To address these issues, sustainable alternatives such as the use of microorganisms (probiotics, bacteriophages, and genetically modified microorganisms) have gained attention. This review examines the effects of these microorganisms on fish aquaculture, focusing on their potential to improve growth, health, and disease resistance while reducing environmental impacts. Probiotics, particularly lactic acid bacteria and yeasts, have been shown to enhance immune responses, digestive enzyme activity, and nutrient absorption in fish. Bacteriophages offer a promising alternative to antibiotics for controlling bacterial pathogens, with studies demonstrating their efficacy in reducing mortality rates in infected fish. Additionally, genetically modified microorganisms (GMMs) have been explored for their ability to produce beneficial compounds, such as enzymes and antimicrobial peptides, which can improve fish health and reduce the need for chemical treatments. Despite their potential, challenges such as regulatory hurdles, public acceptance, and environmental risks must be addressed. This review highlights the importance of further research to optimize the use of microorganisms in aquaculture and underscores their role in promoting sustainable practices. By integrating these biological tools, the aquaculture industry can move towards a more sustainable and environmentally friendly future.

One of the main problems in laboratories of oyster seed production occurs in the stage of settlement or fixation and metamorphosis of the larvae. The organisms develop drastic morphological and physiological changes at this stage, exposing them to attack by pathogenic microorganisms. Numerous studies indicate that before larval settlement to a substrate, they require bacteria to stimulate and induce the process. In this study, Japanese oyster (Crassostrea gigas) larvae were fed with combinations of microalgae and bacteria previously selected for their probiotic potential; their impact on survival, growth, and settlement was evaluated. Larvae D of 12 days old were provided by a private company and transported to the laboratory under controlled conditions. Probiotic bacteria Lactobacillus plantarum 69Cr, L. fermentum 101Cc, and L. casei 43Cg were reactivated on MRS and applied at a concentration of 1×104 CFU mL-1. Microalgae Isochrysis galbana and Chaetoceros calcitrans were grown in F2 medium and supplied at a concentration of 3×104 cells mL-1. Results showed, in all treatments, a survival range of 39-53%, growth of 300-310 μm, and 34-56.5% settlement. However, the best bacteria combined with I. galbana and C. calcitrans was L. plantarum 69Cr with a 54% survival, 310 μm growth, and 56.5% settlement. It is concluded that the combination of L. plantarum 69Cr with I. galbana and C. calcitrans has the potential to be used in the production of Japanese oyster larvae.

Most bacterial diseases in aquaculture production systems are caused by Gram-negative bacteria that belong to the Vibrionaceae family. The administration of probiotics is a promising area of research for the biocontrol and prevention of diseases in aquaculture. In this work, the objective was to investigate three probiotic strains of the genus Lactobacillus. Two trials were performed to determine the mean effective dose of the Lactobacillus strains and the mean lethal dose of the pathogenic Vibrio parahaemolyticus strain. The LD50 for V. parahaemolyticus was 5.5 log CFU mL-1. The three probiotic strains, L. plantarum 69Cr with 104 CFU mL-1, L. fermentum 101Cc with 104 CFU mL-1, and L. casei 43Cg with 103 CFU mL-1 conferred greater survival to the larvae than the control. The bacteria L. plantarum 69Cr and L. fermentum 101Cc conferred protection against the pathogen and significantly improved larval survival with an optimal dose of 104 CFU mL-1, whereas L. casei 43Cg did so with an optimal dose of 103 CFU mL-1. The best survival percentage was achieved when the probiotic L. plantarum 69Cr was supplied. These results indicate that probiotic bacteria associated with, or originating from, Crassostrea gigas can protect their host from a pathogen such as V. parahaemolyticus.