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Microbes & Immunity

ORIGINAL RESEARCH ARTICLE
Identification and characterization of novel outer

membrane proteins of Brachyspira pilosicoli

Amisha Panda 1 , Jahnvi Kapoor 1 , Batchu Hareramadas 2 , Ilmas Naqvi 2 ,
1
4
Ravindresh Chhabra 3 , Sanjiv Kumar * , and Anannya Bandyopadhyay *
1 Department of Zoology, Faculty of Science, University of Delhi, New Delhi, Delhi, India
2 Department of Zoology, Zakir Husain Delhi College, University of Delhi, New Delhi, Delhi, India
3 Department of Biochemistry, School of Basic Sciences, Central University of Punjab, Bathinda,
Punjab, India
4 Independent Researcher, Stockholm, Sweden

Abstract

Brachyspira pilosicoli is a globally prevalent, anaerobic, Gram-negative spirochete that
causes intestinal spirochetosis in birds, pigs, and humans. It colonizes the large intestine,
causing colitis, diarrhea, and impaired growth. Despite its pathogenic relevance,
the outer membrane proteins of B. pilosicoli remain largely uncharacterized. In this
study, we computationally identified a total of 42 outer membrane β-barrel (OMBB)
proteins within the B. pilosicoli proteome using a consensus-based computational
framework. Structural models generated using AlphaFold 3 confirmed the β-barrel
*Corresponding authors: architectures of the predicted proteins. Structure- and sequence-based functional
Anannya Bandyopadhyay annotations revealed homologs of b-barrel assembly machinery BamA protein,
(anannya@zoology.du.ac.in)
Sanjiv Kumar lipopolysaccharide-assembly protein LPS-assembly protein D, TolC, transporter
(drsanjivk@gmail.com) proteins, enzymes, diffusion channels, and porins. Notably, seven of the predicted
OMBB proteins were previously unannotated in UniProt and the National Center for
Citation: Panda A, Kapoor J,
st
Hareramadas B, et al. Identification Biotechnology Information; we report their putative functions here for the 1 time.
and characterization of novel outer Sequence variation analysis among the homologs of OMBB proteins across nine B.
membrane proteins of Brachyspira pilosicoli strains revealed that many of the variations were present within surface-
pilosicoli. Microbes & Immunity.
2025;2(4):79-109. exposed loop regions, suggesting roles in host interaction and immune modulation.
doi: 10.36922/MI025230050 Our in silico study expands the functional repertoire of B. pilosicoli outer membrane
Received: June 6, 2025 proteins, highlighting potential targets for diagnostics, vaccine development, and
therapeutic interventions.
Revised: July 9, 2025
Accepted: August 1, 2025
Keywords: Brachyspira pilosicoli; Intestinal spirochetosis; Outer membrane proteins;
Published online: August 25, 2025 β-barrel structures; Structural models; Sequence variations; Functional annotations;
Copyright: © 2025 Author(s). In silico
This is an Open-Access article
distributed under the terms of the
Creative Commons Attribution
License, permitting distribution,
and reproduction in any medium, 1. Introduction
provided the original work is
properly cited. Brachyspira pilosicoli, previously known as Serpulina pilosicoli, is a zoonotic bacterium
Publisher’s Note: AccScience belonging to the family Brachyspiraceae, within the order Spirochaetales and phylum
Publishing remains neutral with Spirochaetota. It is a Gram-negative, anaerobic, slow-growing, double-membraned,
1
regard to jurisdictional claims in
published maps and institutional flagellated bacterium. B. pilosicoli causes intestinal spirochetosis (IS) in higher animals,
affiliations. including avian intestinal spirochetosis (AIS) in birds, porcine intestinal spirochetosis

Volume 2 Issue 4 (2025) 79 doi: 10.36922/MI025230050