Sissons C H, Hancock E M, Perinpanayagam H E, Cutress T W
Dental Research Unit, Medical Research Council of New Zealand, Wellington.
Arch Oral Biol. 1988;33(10):727-33. doi: 10.1016/0003-9969(88)90006-4.
The origin of ureolytic activity in artificial-mouth plaques was established by assessing the contribution to plaque ureolytic activity of the isolated bacteria. To overcome losses of ureolytic activity caused by the unstable presence of urease in oral bacteria, ureolytic bacteria were isolated from an exceptionally active plaque (1 mumol NH3/min per mg protein) in which 63 per cent of the flora was ureolytic. After their ability to metabolize urea was stabilized, 13 ureolytic bacteria remained: seven strains of Streptococcus salivarius, one Streptococcus bovis, two Staphylococcus epidermidis and three Staphylococcus haemolyticus. Their urease activity, measured after growth into stationary phase, was reproducible and strain specific with a 20-fold range within each genus. The mean ureolytic activity of each species, when weighted by its calculated incidence in the original plaque, accounted for 40 per cent of the total plaque ureolytic activity. However, these values for urease levels were only a small fraction of the bacterial ureolytic potential. Urease per mg cell protein measured during the growth cycle of a selected Strep. salivarius, and Staph. epidermidis, varied 10-fold, and reached much higher activities (i.e. 6-8 mumol NH3/min per mg of cell protein) than under the growth conditions that were used to assess the contribution of these species to total plaque ureolysis. Thus urea metabolism in artificial plaque was due mainly to Strep. salivarius, with a small contribution from Staph. epidermidis. The presence of further unidentified species of ureolytic oral bacteria need not be invoked.
通过评估分离出的细菌对菌斑尿素分解活性的贡献，确定了人工口腔菌斑中尿素分解活性的来源。为了克服口腔细菌中脲酶不稳定存在导致的尿素分解活性损失，从一个活性异常高的菌斑（每毫克蛋白质每分钟产生1微摩尔氨）中分离出尿素分解细菌，其中63%的菌群具有尿素分解能力。在其代谢尿素的能力稳定后，保留了13种尿素分解细菌：7株唾液链球菌、1株牛链球菌、2株表皮葡萄球菌和3株溶血葡萄球菌。它们在进入稳定期后测得的脲酶活性具有可重复性且菌株特异性，每个属内活性范围达20倍。按其在原始菌斑中的计算发生率加权后，每个物种的平均尿素分解活性占菌斑总尿素分解活性的40%。然而，这些脲酶水平的值只是细菌尿素分解潜力的一小部分。在选定的唾液链球菌和表皮葡萄球菌生长周期中测得的每毫克细胞蛋白的脲酶活性变化了10倍，并且达到了比用于评估这些物种对总菌斑尿素分解贡献的生长条件下更高的活性（即每毫克细胞蛋白每分钟6 - 8微摩尔氨）。因此，人工菌斑中的尿素代谢主要归因于唾液链球菌，表皮葡萄球菌的贡献较小。无需考虑是否存在其他未鉴定的口腔尿素分解细菌物种。
