Establishment of oral bacterial communities in germ free mice and the influence of recipient age

Summary

The acquisition of the oral microbiome is a complex process. We examined how the timing of microbial exposure alters bacterial colonization of the tooth surface. Germ-free mice were conventionalized by exposure to specific pathogen free (SPF) mice to acquire a commensal microbiome over three distinct four week periods, 0-4 weeks of age (Conv0-4w), 4-8 weeks (Conv4-8w), or 8-12 weeks (Conv8-12w). Bacterial DNA was extracted from the tooth surface and analyzed by 16S rDNA sequencing. Total bacteria and inflammatory cytokine expression in gingiva were determined by quantitative real-time PCR. After co-housing with SPF mice, Conv0-4wand Conv4-8wmice had low bacterial diversity, while Conv8-12w mice had high bacterial diversity that was similar to SPF donor mice as determined by both the operational taxonomic units and the Shannon Index. Cluster analysis with unweighted Unifrac distance also supported these trends. This was surprising as the amount of maturation time, 4 weeks, was equal in all conventionalized mice and tooth eruption was largely completed by 4 weeks. This suggests that host factors that occur after tooth eruption have a significant effect on the microbial tooth colonization.

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