Ross R A, Madoff L C, Paoletti L C
Channing Laboratory, Department of Medicine, Brigham & Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
J Bacteriol. 1999 Sep;181(17):5389-94. doi: 10.1128/JB.181.17.5389-5394.1999.
Group B Streptococcus (GBS) is the leading cause of bacterial sepsis and meningitis among neonates. While the capsular polysaccharide (CPS) is an important virulence factor of GBS, other cell surface components, such as C proteins, may also play a role in GBS disease. CPS production by GBS type III strain M781 was greater when cells were held at a fast (1.4-h mass-doubling time [td]) than at a slow (11-h td) rate of growth. To further investigate growth rate regulation of CPS production and to investigate production of other cell components, different serotypes and strains of GBS were grown in continuous culture in a semidefined and a complex medium. Samples were obtained after at least five generations at the selected growth rate. Cells and cell-free supernatants were processed immediately, and results from all assays were normalized for cell dry weight. All serotypes (Ia, Ib, and III) and strains (one or two strains per serotype) tested produced at least 3.6-fold more CPS at a td of 1. 4 h than at a td of 11 h. Production of beta C protein by GBS type Ia strain A909 and type Ib strain H36B was also shown to increase at least 5.5-fold with increased growth rate (production at a td of 1. 4 h versus 11 h). The production of alpha C protein by the same strains did not significantly change with increased growth rate. The effect of growth rate on other cell components was also investigated. Production of group B antigen did not change with growth rate, while alkaline phosphatase decreased with increased growth rate. Both CAMP factor and beta-hemolysin production increased fourfold with increased growth rate. Growth rate regulation is specific for select cell components in GBS, including beta C protein, alkaline phosphatase, beta-hemolysin, and CPS production.
B族链球菌（GBS）是新生儿细菌性败血症和脑膜炎的主要病因。虽然荚膜多糖（CPS）是GBS的一种重要毒力因子，但其他细胞表面成分，如C蛋白，也可能在GBS疾病中起作用。III型菌株M781的GBS在细胞以快速（1.4小时质量倍增时间[td]）而非缓慢（11小时td）生长速率培养时产生的CPS更多。为了进一步研究CPS产生的生长速率调节以及其他细胞成分的产生，不同血清型和菌株的GBS在半限定和复杂培养基中进行连续培养。在选定的生长速率下至少经过五代后获取样本。细胞和无细胞上清液立即进行处理，所有测定结果均根据细胞干重进行标准化。所有测试的血清型（Ia、Ib和III）和菌株（每个血清型一或两个菌株）在td为1.4小时时产生的CPS比在td为11小时时至少多3.6倍。Ia型菌株A909和Ib型菌株H36B的β C蛋白产生量也随着生长速率增加至少增加5.5倍（td为1.4小时与11小时时的产生量）。相同菌株的α C蛋白产生量并未随着生长速率增加而显著变化。还研究了生长速率对其他细胞成分的影响。B族抗原的产生量不随生长速率变化，而碱性磷酸酶随着生长速率增加而减少。CAMP因子和β - 溶血素的产生量均随着生长速率增加而增加四倍。生长速率调节对GBS中的特定细胞成分具有特异性，包括β C蛋白、碱性磷酸酶、β - 溶血素和CPS产生。
