Abstract

The skin microbiota is highly variable among fish species and populations and plays a critical role in maintaining fitness, among many functions. Although the skin is in contact with the water environment from hatching onward, little is known about how the skin microbiota is assembled. By using a 16S rRNA gene amplicon sequencing approach, we aimed to describe the skin microbiota of laboratory zebrafish at three developmental stages and to explore the dynamics of the bacterial community at the water-skin interface. Similarly, through culture methods, we investigated potential instances of antibiotic resistance and virulence of skin- and water-isolated microorganisms. Our results showed that water had the highest bacterial diversity and abundance of Amplicon Sequence Variants, while adult skin samples had the lowest diversity. Moreover, we found distinct microbiota compositions in water, adult skin, and young fish samples. Adult skin is inhabited mainly by the phyla Pseudomonadota (47.4%), Actinomycetota (27.7%), Bacillota (14.6%), and Cyanobacteriota (5.9%). Additionally, the skin bacterial isolates showed high antibiotic resistance compared with water-derived isolates, being only susceptible to kanamycin. Our study successfully characterized the skin microbiota of zebrafish, identifying four dominant phyla. We also found that the composition and abundance of skin microbiota changed throughout zebrafish development. Overall, this study provides insights into the dynamic assembly and functional potential of the zebrafish skin microbiota across development.