# The Oral Microbiome in Queensland Free-Ranging Koalas (Phascolarctos cinereus) and Its Association with Age and Periodontal Disease

## TL;DR

This study explores the oral microbiome of wild koalas in Queensland and finds that microbial composition changes with age and oral disease, which could help improve koala health and conservation.

## Contribution

The first detailed characterization of the oral microbiome in free-ranging Queensland koalas and its association with age and periodontal disease.

## Key findings

- Younger koalas had higher Proteobacteria, while Bacteroidetes, Fusobacteria, and Actinobacteria increased with age.
- Fusobacterium and Porphyromonas were more abundant in older koalas and those with periodontal disease.
- Lactobacillus, a potentially beneficial genus, was found only in young koalas (joeys).

## Abstract

The koala (Phascolarctos cinereus), a marsupial native to Australia, is facing serious population decline, partly due to systemic and oral health issues. This study provides the first detailed characterization of the oral microbiome in free-ranging koalas from Queensland using 16S rRNA gene sequencing of oral plaque from individuals across four age groups. Significant age-related shifts in microbial composition were observed. At the phylum level, younger koalas had higher levels of Proteobacteria, while Bacteroidetes, Fusobacteria and Actinobacteria increased with age. At the genus level, older koalas and those with periodontal disease exhibited significantly higher abundances of Fusobacterium and Porphyromonas. Notably, the beneficial genus Lactobacillus was detected only in the joey, suggesting a potential loss of protective microbes with age. These findings reveal distinct microbial patterns associated with age and oral disease, offering valuable insights into koala health and conservation.

This study was developed to profile the oral microbiome of free-ranging Queensland koalas and its association with age, gingivitis and periodontitis. Using next-generation sequencing of 16S rRNA genes, the microbiota of oral plaque samples from eight koalas across different age groups (joey, juvenile, adult and old) were compared. The findings revealed significant shifts in microbiota composition with age and disease presence. At the phylum level, Proteobacteria were the most dominant phylum, especially in younger koalas. Proteobacteria abundance decreased with age, while Bacteroidetes, Fusobacteria and Actinobacteria increased. At the genus level, Acinetobacter declined with age. Fusobacterium and Porphyromonas became more prominent genera in older koalas and those with periodontal disease. The beneficial genus Lactobacillus was detected only in the joey, suggesting a potential loss of protective microbes with age. Alpha diversity analysis showed high variability within individuals based on age. Alpha diversity was remarkably lower in younger koalas and increased with periodontal disease. Beta diversity suggested distinct microbiota composition differences between younger (joey and juvenile) and older (adult and old) koalas, although statistical significance was limited by sample size. This is the first detailed characterization of the oral microbiome in Queensland’s free-ranging koalas and highlights its association with age and oral health status. Findings may contribute to better understanding of oral disease progression in koalas and support conservation and health management efforts.