NCM 2022: Use of Pore-C to explore the 3D organization of animal symbiont chromosomes

As we increasingly appreciate the variability in eukaryotic chromosome biology, the chromosome conformation of only a few model bacteria has been studied so far. Here, we investigate the chromosome spatial arrangement of a longitudinally dividing symbiont thriving in the oral cavity of mammals including humans. Using high-throughput chromosome conformation capture techniques coupled to Oxford Nanopore sequencing, we identified 65 loops engaging 32 different chromosomal regions. Strikingly, loop analysis revealed four regions or domains with different loop densities. From a functional perspective, loops contain genes predicted to be involved in attachment (e.g., adhesins, O-antigen-modifying enzymes) and immune evasion (e.g., immunoglobulin-binding proteins, membrane sialyation, host epithelium permeabilization). Using Pore-C, we conclude that the chromosomes of animal symbionts bear a stable, host-polarized 3D organization that may facilitate animal surface colonization.