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

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, declined with age. and became more prominent genera in older koalas and those with periodontal disease. The beneficial genus 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.