Table 1

The effect of glucose and low pH on the stability of a microbial community. A mixed culture of 9 oral bacteria (representative of those found in health and disease) were grown in a mucin-based medium at a constant pH 7.0. In independent experiments, the culture was pulsed daily on 10 consecutive days with 28 mM glucose. In one culture the pH was maintained throughout the pulsing at pH 7.0, while in other experiments the pH was allowed to fall by bacterial metabolism for 6 hours to pre-set levels of pH 5.5, 5.0 or 4.5. In a final study, the pH was allowed to fall without any pH control imposed [28,29]. Viable counts were determined on selective and non-selective media; proportions are shown after the final glucose pulse for two species implicated in caries and for two species associated with sound enamel

Bacterium

Percentage of total viable count (%)

Pre-pulse

pH 7.0

5.5

5.0

4.5

no pH control

Streptococcus mutans

0.3

1.0

4.2

7.9

9.6

18.9

Lactobacillus rhamnosus

0.1

0.2

2.4

6.2

13.9

36.1

Streptococcus gordonii

28.3

25.0

2.6

6.9

2.7

0.2

Fusobacterium nucleatum

15.2

9.5

7.4

2.3

2.7

<0.001

Marsh BMC Oral Health 2006 6(Suppl 1):S14   doi:10.1186/1472-6831-6-S1-S14