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The aquatic environment, independent of their host, is more favorable to pathogenic bacteria than the terrestrial environment. Consequently, pathogenic bacteria can reach very high densities around aquatic animals and can cause high mortality. The conventional approach, such as antibiotics, has minimal effectiveness. Additionally, due to the emergence of (multiple) resistance, their use is under intense scientific and public scrutiny. Hence, there is a need for the development of alternative control techniques, with an emphasis on prevention, which is likely to be more cost-effective. In this study, a potential bacterial strain Cytobacillus firmus was isolated from polluted river sediment and characterized using a comprehensive range of techniques including biochemical, 16S rRNA sequencing and antibiogram assay. The pathogenicity of the bacteria was tested in vivo on Labeo rohita fingerlings found as non-pathogenic. Further, the bacteria were found to synthesize silver nanoparticles (AgNPs) using AgNO3 as a substrate. The obtained AgNPs were characterized by various methods, including UV-vis spectroscopy, FTIR (Fourier-transform infrared spectroscopy), and Transmission Emission Microscopy (TEM). The study found that the AgNPs were 20 nm in size on average. The antimicrobial activity of synthesized AgNPs was examined against the model freshwater pathogenic bacteria, Edwardsiella tarda and both the MIC (Minimum Inhibitory Concentration) and MBC (Minimum Bactericidal Concentration) were 0.156 µM, while biofilm inhibition activity was also observed at 0.156 µM. The AgNPs showed no haemolytic activity at 0.313 µM. Our findings suggest that C. firmus mediated bacteriogenic AgNPs modulate the activity of common pathogenic bacteria E. tarda. The thoroughness of our research process gives us confidence in the potential of applying AgNPs in aquaculture as a considerable strategy to control the E. tarda infection. [ABSTRACT FROM AUTHOR]

Aquatic food production system raises aquatic organisms including fish, shellfish and seaweeds for human consumption and associated value chains. Moreover, as the global human population continues to expand at a high rate and is expected to reach over 9 billion by 2030, developing a cost-efficient production method is a significant challenge in the future development of the aquatic food production industry to provide food and nutritional security with high-quality animal protein. Recent advancements in biotechnological tools and approaches provided a new toolset that can be used to design and optimize the existing processes such as food preservation, fermentation, packaging, quality control and setting proper guidelines to manufacture and process genetically modified fish. At the same time, with the refinement of technology, these are becoming easier applicable and transferable to several other aquatic species production systems. These trends have resulted in exploiting new and unconventional microbial systems with sophisticated properties, which render promising results in the production industry. Here, we highlight the recent advances in the newly emerging biotechnological technology in the production of fish and fish products and discuss the potential of these tools as a sustainable platform for centuries to come with a significant impact on the aquatic food production industry. [ABSTRACT FROM AUTHOR]