Phage Cocktail Designed for Wastewater Bioremediation Has Limited Effect on Crustacean Filtrator Microbiome Diversity and Health

In this study we investigated the impact of a phage cocktail on Daphnia magna microbiome and the life-history parameters. A mixture of four phages able to infect strains of Klebsiella pneumoniae, Enterobacter sp. and Pseudomonas aeruginosa was tested on three D. magna clones. The host-associated microbiome composition in both the examined variants and the control was analysed using 16S rRNA amplicon sequencing. Additionally, the survival, growth rate, age, size at the first reproduction, and neonate per female were assessed. The analysis revealed minor shifts in microbial composition following phage exposure. Nevertheless, results showed that the phage cocktail increased microbiome diversity. None of the life-history parameters studied were affected by the presence of the phage cocktail, and no adverse effects were observed. The results indicated that under laboratory conditions the phage cocktail is safe for D. magna and its microbiome.