Bacterial 16S rRNA/rDNA Profiling in the Liquid Phase of Human Saliva

F Gu1, #, Y Li3, C Zhou3, D.T.W Wong1, C.M Ho2, F Qi1, W Shi1, *
1 Division of Oral Biology and Medicine, UCLA School of Dentistry, Los Angeles, California 90095
2 Department of Engineering, UCLA Henry Samueli School of Engineering and Applied Sciences, Los Angeles, California 90095
3 Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, NY 10010

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© Gu et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the UCLA School of Dentistry, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA; Tel: 310-825-8356; Fax: 310-794-7109; E-mail:
# Current address: School of Dentistry, University of North Carolina, Chapel Hill, NC27599, USA


Human saliva can be separated by centrifugation into cell pellet and cell-free supernatant, which are called cellular phase and liquid phase in this study. While it is well documented that the cellular phase of saliva contains hundreds of oral bacteria species, little is known whether the liquid phase of saliva contains any information related to oral microbiota. In this study, we analyzed the bacterial nucleic acid contents of the liquid phase of saliva. Using primers universal to most eubacterial 16S rDNA, we detected large amounts of bacterial 16S rRNA and rDNA in the cell-free phase of saliva. Random sequencing analysis of forty PCR amplicons from the cell-free phase of saliva led to 15 operational taxonomic unit (OTU) groups. Furthermore, using denaturing gradient gel electrophoresis (DGGE), we compared 16S rRNA/rDNA profiles derived from liquid phases and cellular phases of saliva samples, and found positive correlations (Pearson Correlation=0.822, P<0.001) between these sample groups. These findings indicate that the liquid phase of saliva contains numerous bacterial 16S rRNA/rDNA molecules that have correlations with bacteria existing in the cellular phase.

Key Words: Saliva, oral bacteria, 16S rRNA, 16S rDNA, DGGE.