Age-related difference in gut microbiota composition and IgA response to gut microbiota

Fecal samples from 40 healthy subjects (adult group: n=20, ; elderly group: n=20) were obtained from healthy subject. Fecal bacteria, no IgA-coatedbacteria in feces and IgA-coated bacteria in feces were collected, respectively. DNA was extracted from bacteria, and analyzed by 16S metagenome sequence based on V3-4 region. Illumina paired-end reads, the bowtie-2 program (ver. 2-2.2.4) was used to remove the reads mapped to PhiX174 sequence and Genome Reference Consortium human build 37. Thereafter, the 3' region of each read with a PHRED quality score of less than 17 was trimmed. Trimmed reads less than 150 bp in length with an average quality score of less than 25 or those lacking paired reads were also removed. The trimmed paired-end reads were combined using the fastq-join script in EA-Utils (ver. 1.1.2–537).