Whole unstimulated saliva was collected from nine pSS patients (age 45–79 years) consisting of eight females and one male, and from nine healthy female controls (age 39–68 years). They all had a normal salivation rate of >1.5 ml in 15 min. All patients fulfilled the revised American European Consensus Group criteria for classification of pSS (9 (link)). DNA was extracted from the samples (200 µl volume) using the MasterPureTM DNA Purification kit (Epicentre, Illumina Company, Madison, WI) and the final DNA was dissolved in 1×TE buffer. The 16S rRNA hypervariable region V1V2 was sequenced on a 454 GS Junior system (Roche, Branford, CT) using the primers (9 (link)) listed in Table 1. Molecular identifier (MID) tags, 10-mer, were used as sample identifiers and are listed in Supplementary Table 1. Amplification reactions were performed as described by Siddiqui et al. (10 (link)), with minor modifications as follows: the cycling program was reduced to 30 cycles and triplicate PCRs were performed for each sample. All PCR products were pooled and purified using Agencourt AMPure PCR purification (Beckman Coulter, Brea, CA). DNA quality and concentration were assessed with Bioanalyzer 2100 (Agilent, Santa Clara, CA) and Nanodrop 3300 Flurospectrometer (Thermo Scientific, Wilmington, DE).