16S rRNA sequencing of saliva
One ml of each participants saliva (Part B only) was centrifuged (13,000 RPM for 3 mins). The supernatant was removed from the pellet and bacterial DNA was extracted from pellets using the GenElute Bacterial Genomic DNA Kit (Sigma-Aldrich, Dorset, UK) according to the manufacturers instructions with the addition of a lysozyme (Sigma-Aldrich) lysis step for 30 minutes at 37 C to aid in the lysis of Gram-positive organisms. Bacterial DNA was eluted into 200 ml elution buffer.