Feeding time changed the diurnal composition of intestinal microbiota in Pelteobagrus fulvidraco

Although the effects of diet on intestinal microbiotas have been well investigated, the effect of feeding time on the rhythm of gut microbiota remains uncertain. A 9-week feeding trial on Pelteobagrus fulvidraco was conducted. Two triplicate groups of fish were fed identically either at 8:00 (day) or at 20:00 (night). After 9 weeks, three fish from each cage were sacrificed every 4 h for 24 h. The intestinal contents were analyzed using high-throughput sequencing. Three phyla (Fusobacteria, Proteobacteria, and Verrucomicrobia), and three genera (Cetobacterium, Akkermansia, and Clostridium) were dominant at every time point. Moreover, 33.02% of detected amplicon sequence variants showed cyclical variations in fish fed at 20:00, and 3.47% in fish fed at 8:00. Among the top 20 genera, 17 showed cyclical variations in the 20:00 group, and only two in the 8:00 group. Rhodobacter, Ralstonia, Mycobacterium, Lactococcus, Halomonas, Akkermansia, and Acinetobacter contributed more to the predicted functional pathways. Moreover, 144 and 38 pathways exhibited daily cyclical fluctuations in fish fed at 20:00 and 8:00, respectively. Overall, certain intestinal microorganisms showed a circadian rhythm in P. fulvidraco, and this circadian rhythm was affected by shifted feeding times.