16s rRNA sequencing of stool pellets from IEC-Bmal1-/- mice and Bmal1flox controls in naive and DSS-treated states over the course of a day

Circadian clocks are important for gut health. This experiment aimed to determine the role of core clock gene Bmal1 in regulating microbial rhythmicity in health and dextran sulphate sodium induced colitis. Mice were generated with Bmal1 selectively deleted in Villin-expressing cells (predominantly IECs).Microbial DNA was extracted from fecal pellets collected from IEC-Bmal1-/- and Bmal1flox mice (aged 8-19 weeks) at zeitgeber time 0, 4, 8, 12, 16, 20 across the 24h day with the DNeasy PowerSoil Pro Kit (Qiagen), as per manufacturer's instructions. Pre-amplification of the V4 region of 16S rRNA was performed using forward primer 5'-ACACTCTTTCCCTACACGACGCTCTTCCGAT-CTNNNNNGTGCCAGCMGCCGCGGTAA-3' (annealing sites in bold) and reverse primer 5'-GTGACTGGAGTTCAGACGTGTGCTCTTCCGATCTGGACTACHVGGGTWTCTAAT-3'. Sequencing was performed by the University of Liverpool Centre for genomics Research, using the Illumina MiSeq v2 platform (Illumina), generating 250bp paired-end reads. PhiX control v3 library (PhiX) was spiked into samples to balance low base diversity often found in microbiome samples. Quality control was performed and OTU tables were generated using a pipeline provided by the University of Manchester Bioinformatics Core Facility local Galaxy service. Briefly, VSEARCH clustered OTUs and removed chimeras. The OTU database was mapped to the SILVA (v138) reference database with >97% homology threshold. All samples passed quality checks and had sequence depth >45,000. The OTU table was analysed using R packages phyloseq, vegan, limma and ALDEx2. JTK_CYCLE 93 was used to identify rhythmic OTUs with a period of 24 h and an adjusted P value < 0.05.