mutans (Table 1). Spearman’s correlation coefficients (r2) obtained from the paired samples with or without PI demonstrated a high degree of correlation in the mean CFU counts (Fig. 1a–d). PCR amplification of 16S rRNA gene fragments of 300 bp from 22 paired saliva

and 22 paired ETSA plates were profiled by DGGE. The banding patterns were first normalized and then compared between the two groups (with or without PI), based on the position and intensity of each detected band. No difference between the two groups was observed in the numbers of detected DGGE bands (Table 2) or in the total DGGE profiles, for either the saliva samples (Fig. 2a) or the total cultivable samples from ETSA plates (Fig. 2b). The dendrograms clearly learn more demonstrated that all 22 pairs were placed in the same branch. The mean Cs between the paired samples was 97.4% (ranging from 92.7% to 100%) for the buy SGI-1776 saliva samples and 95.8% (ranging from 85.7% to 100%) for the total cultivable

samples. To determine the effects of PI on the integrity of saliva proteins, the saliva samples treated with and without PI were analyzed by 1D SDS-PAGE and LC-MS/MS (Fig. 3). No significant differences were observed among the protein bands between the treated and the untreated samples. Using a combination of in-gel digestion and LC-MS/MS analysis, we identified approximately 600 proteins with high confidence for each gel lane. The spectra counts of the major saliva proteins do not show any changes larger than twofold, indicating that the inclusion of PI did not have a significant impact

on the integrity or stability of salivary proteins. To investigate any effects of the inhibitors on peptidase activity, we analyzed the low-molecular-weight species in the saliva. The molecular ions of the Cyclooxygenase (COX) low-molecular-weight species were detected (Fig. 4). We found the major ions to be identical for both treated and untreated saliva samples. By a database search, it was observed that most of the ions detected in the LC-MS/MS analysis are fragments of proline-rich proteins. Proteases play important roles in a multitude of physiological reactions and biological functions of most microorganisms. Intracellularly, they maintain whole-protein homeostasis by (1) controlling the degradation of proteins, which are involved in cell cycle and bacterial development and (2) responding properly to environmental changes such as stress (Gottesman, 1996; Prepiak & Dubnau, 2007). Extracellularly, a direct relationship with the inactivation of foreign proteins and the destruction of connective-tissue components has been reported (Supuran et al., 2002). Protease inhibitors can alter cell regulation, differentiation, and physiologic functions of microorganisms (Travis & Potempa, 2000), and they have been used as antibacterial agents.