The basis of antigenic operon fragmentation in Bacteroidota and commensalism.

"Using the classical lipopolysaccharide/O-antigen rfb operon in Enterobacteriaceae as a surface antigen model (5-gene-cluster rfbABCDX), and a recent rfbA-typing strategy for strain classification, we characterized the architecture/conservancy of the entire rfb operon in Bacteroidota. Bacteroides-insertions, also detected in other antigenic operons (fimbriae), but not in operons deemed essential (ribosomal), could explain why Bacteroidota have fewer KEGG-pathways despite large genomes. Mechanistically, genomic sequence analyses revealed that operon fragmentation is driven by intra-operon insertions of predominantly Bacteroides-DNA (thetaiotaomicron/fragilis) and likely natural selection in specific micro-niches. [Extracted from the article]