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. 2011 Sep 23;6(9):e25299. doi: 10.1371/journal.pone.0025299

Figure 4. pH in planktonic suspension.

Figure 4

A. Overnight cultures of S. oralis SK248, A. naeslundii AK6, S. mitis SK24, S. downei HG594, and S. sanguinis SK150 were washed twice and suspended in sterile saliva containing 0.4% (w/v) glucose. pH was measured after 30 min, 4 h and 20 h. All Streptococcus spp. reached terminal pH within four hours. pH drops in suspensions of A. naeslundii occurred more slowly. B. When glucose concentration was raised to 10% (w/v), no differences in terminal pH were observed. After 20 h, pH was lowest for S. sanguinis and S. downei (4.3–4.4) and highest for S. mitis SK24 (4.9–5). In suspensions of A. naeslundii, pH dropped more quickly as compared to 0.4% glucose. Experiments were performed in duplicate and repeated on another day. Error bars indicate standard deviations.