The composition of the zebrafish intestinal microbial community varies under Bdellivibrio treatment from larvae to juveniles and adults.

Bdellivibrio could be recognized for its efficacy as a "living antibiotic" against Gram-negative bacteria and holds potential applications in aquaculture. Nevertheless, the safety implications of prolonged Bdellivibrio administration in aquaculture remain unexplored. This study aimed to investigate the impact of continuous Bdellovibrio supplementation to zebrafish culturing water over a 6-month period, spanning from larvae to adult fish. Assessments encompassed the influence on growth indicators, intestinal flora distribution, and resistance to pathogenic bacterial infections. Contrary to expectations, Bdellovibrio exhibited minimal effects on the growth parameters (body length and weight) of zebrafish, however, a notable increase in survival rates was observed. 16S rRNA sequencing revealed a significant enhancement in the diversity and abundance of intestinal microorganisms in zebrafish. Notably, the abundance of Planctomycetes increased, while potential pathogenic bacteria such as Aeromonas, Pirellula, and Flavobacterium decreased in the zebrafish intestine. Under Edwardsiella anguillarum immersion infections, Bdellovibrio significantly boosted the survival rate of zebrafish, concomitant with a continuous rise in Bdellovibrio levels in the breeding water. This comprehensive analysis sheds light on the safety of prolonged Bdellovibrio use and its protective efficacy against pathogenic bacterial infections. The findings not only elucidate the mechanisms through which Bdellovibrio safeguards fish from bacterial infections but also furnish essential theoretical foundations for the secure integration of Bdellovibrio in aquaculture. • Long-term use of Bdellovibrio has not adversely effects on the growth of zebrafish. • Bdellovibrio could significantly increase the diversity and abundance of zebrafish intestinal microorganisms. • The Bdellovibrio could increase the abundance of Planctomycetes, and decrease the potential pathogenic bacteria in zebrafish intestine. • Bdellovibrio could significantly increase the survival rate of zebrafish under E. anguillarum immersion infections. [ABSTRACT FROM AUTHOR]