Zebrafish larvae metagenome following probiotic administration and photoperiod manipulation

The microbiota plays a fundamental role in maintaining host’s health by controlling a wide range of physiological processes. Administration of probiotic and manipulation of photoperiod have been proven able to modulate microbial composition and are currently undergoing an extensive research in aquaculture as a way to improve health and quality of harvested fish. However, our understanding regarding their effects on the physiological processes is still limited. In the present study we investigated whether manipulation of photoperiod and/or probiotic administration was able to alter microbial composition in zebrafish larvae at hatching and tried to link dysbiosis to biological activity. To this extent, zebrafish (Danio rerio) were spawned individually and at hatching (about 72 hpf) larvae were divided into 3 groups: one group was exposed to a 12:12 h light:dark cycle (LD), one group exposed to 24 hrs of continuous light (LL) and one group exposed to 24 h of continuous darkness (DD). Each group received two different treatments: control (C) or probiotic (P) (L. rhamnosus). After 24 h of exposure, at the same time in the morning, larvae were euthanised and subjected to sequencing of the V3-V4 variable regions of the 16S rRNA gene.