PHYSICAL AND BIOCHEMICAL-STUDIES OF STREPTOCOCCUS-MUTANS SEDIMENTS SUGGEST NEW FACTORS LINKING THE CARIOGENICITY OF PLAQUE WITH ITS EXTRACELLULAR POLYSACCHARIDE CONTENT
PHYSICAL AND BIOCHEMICAL-STUDIES OF STREPTOCOCCUS-MUTANS SEDIMENTS SUGGEST NEW FACTORS LINKING THE CARIOGENICITY OF PLAQUE WITH ITS EXTRACELLULAR POLYSACCHARIDE CONTENT
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DOI：
10.1177/00220345880670060101
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发表时间：
1988-06-01
影响因子：
7.6
通讯作者：
SHELLIS, RP
中科院分区：
文献类型：
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作者：
DIBDIN, GH;SHELLIS, RP
变形链球菌MFe 28（血清型H）的培养物在不同的胞外多糖（EPS）含量下生长。生物化学和物理化学特性被认为是相关的龋齿进行了测量。在pH-stat中测得的产酸参数为：Vm = 0.76 ± 0.95。0.14μ mol/g/sec（湿重）;表观Km（产酸量）= 100 μ mol/L;摩尔产率= 1.97 ±。0.25 mol酸/mol葡萄糖。还注意到酸阴离子对酸产生的抑制。通过纯洗涤的细菌残留物进行缓冲需要约112 μ mol碱/g（湿重）残渣将pH从4改变到6.5，当EPS含量增加到100%时，pH几乎下降到零。残留物中的扩散系数（D）在很宽的范围内与EPS含量无关。当使用渗出液法时，De（葡萄糖）和De（乙酸盐）为（3.26 ± 0.01）。0.6)和（5.05 .+-. 0.8). times. 10-6 cm 2/sec。通过菊粉排除法测量的细胞外液分数从纯细菌的0.33增加到纯EPS的0.78。它示出了如何，仅通过这些因素，而不需要任何扩散限制，菌斑EPS可能会导致牙齿表面的pH值较低，从而增加了致龋的挑战。
Cultures of Streptococcus mutans MFe28 (serotype H) were grown with differing extracellular polysaccharide (EPS) content. Biochemical and physicochemical characteristics considered relevant to caries were measured. Acid production parameters measured in a pH-stat were: Vm = 0.76 .+-. 0.14 .mu.mol/g/sec (wet weight); apparent Km (acid production) = 100 .mu.mol/L; molar yield = 1.97 .+-. 0.25 mol acid/mol glucose. Acid anion inhibition of acid production was also noted. Buffering by the pure washed bacterial residue required approx. 112 .mu.mol of base/g (wet weight) of residue to change the pH from 4 to 6.5, and this dropped almost to zero as the EPS content increased to 100%. Diffusion coefficients (D) in the residues were independent of EPS content over a wide range. When the effusion method was used, De (glucose) and De (acetate) were (3.26 .+-. 0.6) and (5.05 .+-. 0.8) .times. 10-6 cm2/sec, respectively. The extracellular fluid fraction, measured by inulin exclusion, increased from 0.33 for the pure bacteria to 0.78 for the pure EPS. It is shown how, by these factors alone, and without any need for diffusion restriction, plaque EPS may lead to a lower pH at the tooth surface, thus increasing the cariogenic challenge.