A host-adapted auxotrophic gut symbiont induces mucosal immunodeficiency

The microbiome holds great promise as a source of novel therapeutic targets for many diseases. Mining for causative microorganisms that impact processes underlying disease states should utilize Koch’s postulates. Here we show a functional screen for the bacterial microbiota of intestinal immunoglobulin A (IgA)-deficient mice; we identified a novel Gram-negative bacterium, proposed to be named as Tomasiella immunophila that induces and degrades IgA in mouse intestine. T. immunophila is auxotrophic for the bacterial cell wall amino sugar N-acetylmuramic acid (MurNAc). T. immunophila secretes IgA-degrading enzymes into outer membrane vesicles that preferentially degrade rodent antibodies with kappa but not lambda light chains. We propose this study uncovers a new paradigm for the role of symbionts in immunodeficiency that can ultimately be applied to human disease., This dataset consists of a phylogenomic tree, generated using Phylophlan3., , # Tree from the manuscript: A host-adapted auxotrophic gut symbiont induces mucosal immunodeficiency [https://doi.org/10.5061/dryad.j0zpc86p8](https://doi.org/10.5061/dryad.j0zpc86p8) This tree highlights the separation of the novel genus, *Tomasiella*, from its close relatives within the family *Muribaculaceae*. ## Description of the data and file structure The NEXUS file for the tree from our manuscript, Figure 2A, is available.