Robinson J M, Hardman J K, Sloan G L
J Bacteriol. 1979 Mar;137(3):1158-64. doi: 10.1128/jb.137.3.1158-1164.1979.
Mutants of Staphylococcus staphylolyticus incapable of producing an extracellular staphylolytic glycylglycine endopeptidase were isolated and found to have cells in the population susceptible to lysis by this enzyme, as did the wild-type organism under conditions in which the endopeptidase was not produced. These results suggest that cultures of this organism normally contain a heterogeneous population of cells with regard to cell wall composition and susceptibility to the enzyme. Production of the endopeptidase appears to act as a selective pressure which removes the susceptible cells in the population as the enzyme appears in the medium. A comparison of the peptidoglycan of the wild-type organism grown under conditions in which the endopeptidase was produced with that of this organism grown under nonproducing conditions and with those of endopeptidase-less mutants showed that in the presence of the endopeptidase the cell population had peptidoglycan with shorter peptide cross bridges and a greater percentage of serine in these cross bridges than was found in cells grown in the absence of the enzyme. The inability of the endopeptidase to hydrolyze glycylserine and serylglycine peptide bonds suggests that at least part of the resistance this organism has to the endopeptidase is due to relative amounts of serine found in the peptide cross bridges of some cells in the population.
分离出了不能产生细胞外溶葡萄球菌甘氨酰甘氨酸内肽酶的溶葡萄球菌突变体，发现群体中的细胞与野生型生物体一样，在不产生内肽酶的条件下易被该酶裂解。这些结果表明，就细胞壁组成和对该酶的敏感性而言，该生物体的培养物通常含有异质细胞群体。内肽酶的产生似乎起到了一种选择压力的作用，随着酶出现在培养基中，它会去除群体中的易感细胞。将在产生内肽酶的条件下生长的野生型生物体的肽聚糖与在不产生内肽酶的条件下生长的该生物体的肽聚糖以及无内肽酶突变体的肽聚糖进行比较，结果表明，在内肽酶存在的情况下，细胞群体的肽聚糖肽交联桥较短，且这些交联桥中丝氨酸的百分比高于在无酶条件下生长的细胞。内肽酶无法水解甘氨酰丝氨酸和丝氨酰甘氨酸肽键，这表明该生物体对该内肽酶的抗性至少部分归因于群体中某些细胞的肽交联桥中丝氨酸的相对含量。
