As an alternative approach to identifying bacterial microorganisms present in lymph node tissue, we utilized amplicon DNA library sequencing technology. The hypervariable region V6 of the 16S rRNA gene was used because it has been reported to differentiate between many bacterial species [39] . Amplicon libraries of V6 were generated from the 454 cDNA libraries of MD 257, MD 80228, and MD OCT-pool and subjected to multiplex pyrosequencing on a Roche GS FLX sequencer (for properties of amplicon sequencing runs, see Table S1 ). The V6 amplicon rRNA tags were evaluated using the RDP classifier tool (Table S5) .