**5. Conclusions**

In summary, using three healthy adult volunteers as our subjects, our study demonstrated that a daily consumption of 1.0 L oolong tea for eight weeks caused a reduction in bacterial community diversity, as well as the disturbance of hub salivary bacterium with strong connections to other salivary microbiota. Additionally, it was also noticed that large inter-individual variations were found, implying diverse responses to oolong tea consumption may exist among subjects. Larger sample sizes and more in-depth mechanism studies are necessary to further clarify and elucidate the physiological relevance of the shifts of salivary microbiota to the oral health of the host.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2072-6643/12/4/966/s1, Figure S1: Chromatograms obtained from oolong tea infusion, using UHPLC Q-TOF-MS/MS in negative and positive ion modes, Figure S2: PCA score plot based on the relative abundance of all OTUs of the three subjects, Table S1: Summary of the sequencing results of all salivary samples.

**Author Contributions:** Conceptualization, Z.L., W.Z., and L.N.; formal analysis, Z.L. and H.G.; main funding acquisition, L.N.; investigation, Z.L., H.G., and W.Z.; project administration, L.N.; supervision, L.N.; visualization, Z.L.; writing—original draft, Z.L.; writing—review and editing, Z.L., W.Z., and L.N. All authors read and approved the final manuscript.

**Funding:** This study was supported by the National Key Research and Development Plan of China (no. 2016YFD0400801).

**Acknowledgments:** The authors thank Jun Lin, Fujian Agriculture and Forestry University, for his excellent technical assistance.

**Conflicts of Interest:** The authors declare no conflicts of interest.
