# Exploring the associations between preen oil bacterial, chemical and proteomic profiles of passerines

## TL;DR

This study explores the connections between bacteria, chemicals, and proteins in preen oil from eight bird species, revealing possible roles in producing signals and antimicrobial compounds.

## Contribution

First characterization of preen oil chemical and proteomic profiles in passerines and exploration of bacteriome contributions.

## Key findings

- Preen oil profiles varied among birds, with bacteria like Streptococcus and Corynebacterium being common.
- Chemical profiles included alcohols, ketones, and carboxylic acids, while proteomic functions included proteolysis and stress response.
- Riparian species showed higher chemical diversity and more mVOC-producing bacteria, suggesting habitat-specific adaptations.

## Abstract

Preen gland bacteria are thought to be the key producers of preen oil components such as chemosignalling molecules including volatile organic compounds (VOCs) and antimicrobial compounds including peptides and antimicrobial VOCs. However, data on the preen oil bacteriome and chemical composition are limited to a small subset of bird species, and the presence of antimicrobial peptides is largely unexplored. Here, we performed an exploratory study to characterize, for the first time, the preen oil chemical and proteomic profiles and to explore the possible contribution of the bacteriome to the production of preen oil VOCs and antimicrobial peptides (bacteriocins) in eight passerine species, each represented by a single individual. Preen oil bacteriome, chemical and proteomic profiles varied among birds. The bacterial profiles were dominated by the genera Streptococcus, Lactococcus, Corynebacterium and Cutibacterium. The chemical profiles mainly consisted of alcohols, ketones and carboxylic acids. The biological functions primarily associated with the proteomic profiles were proteolysis and response to oxidative stress. Although we were unable to explore a direct association between the bacteriome and chemical profiles, the preen oil contained bacteriocin- and VOC-producing bacterial genera capable of producing detected microbially-derived VOCs (mVOCs), the relative abundance of which varied between birds. Riparian species showed the highest chemical diversity and high abundances of putative preen oil mVOC-producing bacteria, which could suggest habitat-specific adaptations. This exploratory study may significantly contribute to the formulation of hypotheses on the potential role of host ecological factors in the variation of preen oil bacterial, chemical and proteomic profiles in passerines.

The online version contains supplementary material available at 10.1007/s10482-025-02182-w.