Specific Time Determinism: Circadian Rhythm of Microbial Community Assembly Patterns Under Common Light in Feces of Laying Hens

Abstract

BackgroundAs an important part of biological rhythm, the circadian rhythm of the gut microbiota plays a crucial role in host health. However, few studies have determined the associations between the circadian rhythm and gut microbiota in laying hens. The purpose of this experiment was to investigate the circadian rhythm of the feces microbiota in laying hens.ResultsFeces samples were collected from ten laying hens at nine different time points (06:00-12:00-18:00-00:00-06:00-12:00-18:00-00:00-06:00) to demonstrate the diurnal oscillation of the feces microbiota. We described the phenomenon of circadian rhythmicity of the feces microbiota in laying hens based on 16S rRNA gene sequencing. According to the results, the α and β diversity of the feces microbiota fluctuated significantly at different time points. Beta Nearest Taxon Index analysis suggested that assembly strategies of the abundant and rare amplicon sequence variants (ASVs) sub-communities are different. Abundant ASVs preferred disperal limitation (weak selction), whereas rare ASVs randomly formed due to the “non-dominant” fractions. Highly robust circadian fluctuations were found, for instance, in Firmicutes and Proteobacteria, which fluctuated oppositely, and the total ratio remained in a dynamic balance over 48 h. We found that temporal dynamic changes had a significant effect on the relative abundance of the important bacteria in the feces microbiota community by using the random forest algorithm. Eight bacteria, Ruminococcus gnavus, Faecalibacterium, Ruminococcaceae, Enterococcus cecorum, Lachnospiraceae, Clostridium, Clostridiales, and Megamonas, gained rhythmicity. Interestingly, one unexpected finding was the fact that these eight bacteria all belong to Firmicutes. In particular, the microbiota profile appears to favor butyrate production, a common indicator of gut health, potentially through increases in the members of Lachnospiraceae, Faecalibacterium and Ruminococcaceae. The pathways were the functionalities that gained rhythmicity within the microbiota, which belonged to the most abundant functions, including xenobiotic biodegradation and metabolism, carbohydrate metabolism, and amino acid metabolism, which were consistent with the metabolic functions of amino acids and carbohydrates from feed.ConclusionThis study has shown that the defecation time could be among the important factors influencing the diversity, proportion, and functions of the feces microbiota community. We also note the potential application of beneficial microbial communities in livestock species, especially in the environment of raising antibiotic-free animals. These results provide references for further exploring the circadian rhythm of the gut microbiota in laying hens.