ena-STUDY-ABERSYTWYTH UNIVERSITY-31-03-2015-14:15:56:684-143
The Human Salivary Microbiome exhibits Seasonal changes in Bacterial load but not Diversity
It is well established that incidence of upper respiratory tract infections vary throughout the year, and it may be expected that the salivary microbiome would reflect this. To determine this, the saliva of 40 participants was collected every two months during a 12 day period, from October 2012 to October 2013, alongside lifestyle information. Samples were analysed in terms of bacterial load, through quantitative PCR, and measurement of pH. A sub-group of ten participants, selected because of their similar lifestyle information, underwent sequencing of the V3 to V4 region of the 16S rRNA gene. Estimated bacterial load was shown to be significantly (P < 0.001) higher in February 2013 than at all other sampling time points, with individuals’ changes between time points displaying significant (P = 0.003) flux. Salivary pH levels were shown to be significantly (P < 0.001) higher in December 2012 than in October 2012 and February 2013, with significant (P < 0.001) individual variations seen across the sampling period. In regards to the stability of the taxonomic composition of the salivary microbiome, a-diversity values showed significant differences between participants (P < 0.001), but not between sampling periods (P = 0.801), and a small, but significant positive correlation with salivary pH (R2 = 7.8%; P = 0.019). At the phylum level of classification, significant differences were evident between participants in the Actinobacteria (P < 0.001), Bacteroidetes (P < 0.001), Firmicutes (P = 0.008), Fusobacteria (P < 0.001), Proteobacteria (P < 0.001), Synergistetes (P < 0.001), and Spirochaetes (P = 0.003) phyla. The salivary microbiome shows temporal stability in terms of bacterial taxonomic diversity, but not load, over a one year period. This work suggests that comparing the human salivary microbiome at different time points over the year is valid, as minimal temporal variability is shown.
It is well established that incidence of upper respiratory tract infections vary throughout the year, and it may be expected that the salivary microbiome would reflect this. To determine this, the saliva of 40 participants was collected every two months during a 12 day period, from October 2012 to October 2013, alongside lifestyle information. Samples were analysed in terms of bacterial load, through quantitative PCR, and measurement of pH. A sub-group of ten participants, selected because of their similar lifestyle information, underwent sequencing of the V3 to V4 region of the 16S rRNA gene. Estimated bacterial load was shown to be significantly (P < 0.001) higher in February 2013 than at all other sampling time points, with individuals’ changes between time points displaying significant (P = 0.003) flux. Salivary pH levels were shown to be significantly (P < 0.001) higher in December 2012 than in October 2012 and February 2013, with significant (P < 0.001) individual variations seen across the sampling period. In regards to the stability of the taxonomic composition of the salivary microbiome, a-diversity values showed significant differences between participants (P < 0.001), but not between sampling periods (P = 0.801), and a small, but significant positive correlation with salivary pH (R2 = 7.8%; P = 0.019). At the phylum level of classification, significant differences were evident between participants in the Actinobacteria (P < 0.001), Bacteroidetes (P < 0.001), Firmicutes (P = 0.008), Fusobacteria (P < 0.001), Proteobacteria (P < 0.001), Synergistetes (P < 0.001), and Spirochaetes (P = 0.003) phyla. The salivary microbiome shows temporal stability in terms of bacterial taxonomic diversity, but not load, over a one year period. This work suggests that comparing the human salivary microbiome at different time points over the year is valid, as minimal temporal variability is shown.