Recent research has unveiled the pivotal role of anaerobic bacteria in maintaining fish health and homeostasis of the intestinal microbiome. Most previous studies have identified Fusobacteria and Cetobacterium as prominent inhabitants of the gut microbiota in freshwater fish. Nevertheless, it is only in recent years that Cetobacterium species have been isolated and characterized.
In this study, we report the isolation of Cetobacterium sp. from the intestines of juvenile Nile tilapia (O. niloticus). This bacterium was successfully cultured, and in vitro characterized, based on whole genome sequencing, evaluation of bacterial survival on bile salts (0,3%) and low pH, extracellular enzyme production, antibacterial activity, intestinal adhesion potential, and safety aspects, including toxin production and antibiotic resistance.
Our findings reveal the potential of Cetobacterium as a probiotic candidate for Nile tilapia culture. The in vitro assessment demonstrated the probiotic potential of Cetobacterium, suggesting its ability to survive and colonize in the intestines.
To further explore its practical application, in vivo experiments were carried out by administrating Cetobacterium sp. 1x10^6 CFU/g to tilapia fingerlings for 5 days. The results of these experiments provide valuable insights into the potential benefits of using Cetobacterium sp. as a probiotic in fish culture due to the bacterial colonization and regulation of intestine microbiota and modulation of the immune system as seen by transcriptomic analysis of head kidney in treated fish vs control group.
This study underscores the importance of understanding and harnessing the role of anaerobic bacteria, such as Cetobacterium in promoting fish health and enhancing the sustainability of aquaculture practices. The findings presented here contribute to the growing body of knowledge on probiotics in aquaculture and open new avenues for improving fish gut microbiome homeostasis and overall fish health.