# Parabacteroides vesiculifaciens sp. nov., a Novel Immunomodulatory, Vesicle-Producing Gut Commensal Isolated from the Human Gut

## TL;DR

Scientists discovered a new gut bacteria species, Parabacteroides vesiculifaciens, which produces immune-affecting vesicles and has unique genetic and metabolic traits.

## Contribution

Identification of a novel gut commensal species with immunomodulatory properties and vesicle production capabilities.

## Key findings

- Strain ASD2025T is a new Parabacteroides species with distinct genomic and phenotypic features.
- The strain produces extracellular vesicles and modulates immune responses in HT29 cells.
- The genome contains antibiotic resistance genes and prophage elements.

## Abstract

The genus Parabacteroides comprises widespread gastrointestinal commensals, known to produce immunomodulatory molecules and extracellular vesicles, yet its full diversity is incompletely cataloged. This study describes strain ASD2025T, isolated from healthy child feces, using a polyphasic taxonomic approach including phenotypic profiling, chemotaxonomy, and comparative genomics. Cells were non-motile, polymorphic rods that produced extracellular vesicles. Phylogenomic analysis placed ASD2025T within the genus Parabacteroides within a species complex consisting of P. acidifaciens, P. hominis, “P. massiliensis”, P. merdae, and P. johnsonii, with average nucleotide identities to the type strains of 85.5–89.9%. The large genome (5.16 Mbp, 46.2% GC content) contained integrative conjugative elements harboring antibiotic resistance genes and hankyphage-related prophage. The strain produced succinate as the major metabolic end product, and its major fatty acids were anteiso-C15:0, iso-C17:0 3-OH, and C15:0. Conditioned medium from ASD2025T antagonized the interleukin-8 response caused by E. coli lipopolysaccharide in HT29 cells. The majority of related metagenome-assembled genomes originate from mouse microbiomes. Based on these distinct characteristics, strain ASD2025T (=VKM B-3926T = JCM 37967T) represents a novel species of the genus Parabacteroides, for which the name Parabacteroides vesiculifaciens sp. nov. is proposed.