Great Tit (Parus major) Uropygial Gland Microbiomes and Their Potential Defensive Roles

Abstract

The uropygial gland (preen gland) of birds plays an important role in maintaining feather integrity and hygiene. Although a few studies have demonstrated potential defensive roles of bacteria residing within these glands, the diversity and functions of the uropygial gland microbiota are largely unknown. Therefore, we investigated the microbiota of great tit ( Parus major ) uropygial glands through both isolation of bacteria (culture-dependent) and 16S rRNA amplicon sequencing (culture-independent). Co-culture experiments of selected bacterial isolates with four known feather-degrading bacteria ( Bacillus licheniformis , Kocuria rhizophila , Pseudomonas monteilii , and Dermacoccus nishinomiyaensis ), two non-feather degrading feather bacteria, one common soil bacterial pathogen and two common fungal pathogens enabled us to evaluate the potential antimicrobial properties of these isolates. Our results show major differences between bacterial communities characterized using culture-dependent and -independent approaches. In the former, we were only able to isolate 12 bacterial genera (dominated by members of the Firmicutes and Actinobacteria), while amplicon sequencing identified 110 bacterial genera (dominated by Firmicutes, Bacteroidetes, and Proteobacteria). Uropygial gland bacterial isolates belonging to the genera Bacillus and Kocuria were able to suppress the growth of four of the nine tested antagonists, attesting to potential defensive roles. However, these bacterial genera were infrequent in our MiSeq results suggesting that the isolated bacteria may not be obligate gland symbionts. Furthermore, bacterial functional predictions using 16S rRNA sequences also revealed the ability of uropygial gland bacteria to produce secondary metabolites with antimicrobial properties, such as terpenes. Our findings support that uropygial gland bacteria may play a role in feather health and that bacterial symbionts might act as defensive microbes. Future investigations of these bacterial communities, with targeted approaches (e.g., bacterial isolation and chemical analyses), are thus warranted to improve our understanding of the evolution and function of these host-microbe interactions.

Habitat shapes diversity of gut microbiomes in a wild population of blue titsCyanistes caeruleus

“…In the most robust study to date (Goodenough et al 2017), no skin-related bacterial taxa were found to be dominant or differentially prevalent in our study. Similarly, taxa associated with uropygial gland secretions (that often are later identified on bird skin) in the closely related great tit do not overlap convincingly with our ASVs (Bodawatta et al 2020a). More work is needed to understand the variation of bird microbiomes across different body regions and how cross-contamination could confound results in studies like ours.…”

Dynamics of Microbial Communities on Eggshells and on Nest Materials During Incubation in the Oriental Tit (Parus Minor)

“…More likely is that the microbes originating from parents shape the dynamics in eggshell microbial community during incubation [10,11,43,44]. For instance, we found noticeable increase in the proportion of Firmicutes on the eggshell and Firmicutes include species of microbes present in uropygial gland [45] gastrointestinal tract [38,46,47], or feathers [48]. It is plausible that the microbes originating from parents, either through contact with cloaca (when laying) or with uropygial gland and feathers (during incubation), are transferred once or continuously to the eggshell and shape the dynamics and phylogenetic turnover in eggshell microbial community.…”

Exploring the Ecological Implications of Microbiota Diversity in Birds: Natural Barriers Against Avian Malaria

“…These results suggest a possible interaction between infection and microbiota. Some microorganisms have been identified as potential symbionts in the uropygial gland ( 41 ). Based on functional predictions using 16S rRNA sequences, uropygial gland bacteria were suggested to produce metabolites with antimicrobial properties, such as terpenes ( 41 ).…”