WOOD W B, SMITH M R
J Exp Med. 1949 Jul;90(1):85-96. doi: 10.1084/jem.90.1.85.
Five strains of type III pneumococcus have been shown to possess wide capsular slime layers during the logarithmic phase of growth in serum broth. The slime layer stains metachromatically with methylene blue and can be visualized under the electron microscope as a fuzzy halo which extends well beyond the surace of the capsule proper and causes centrifugates of the organism to be of extremely large volume. This outer capsular structure is most readily demonstrated in vivo and in nutrient broth containing glucose and serum. It disappears from the surface of the cell with aging of the culture, and is easily removed by dilute alkali, alcohol, and heat. Exposure of slime-covered type III pneumococci to homologous antibody and to type III polysaccharidase reveals that the slime layer contains the same type-specific polysaccharide that is present in the rest of the capsule. From a type III strain producing a prominent slime layer an intermediate mutant has been isolated which forms small non-mucoid colonies on blood agar and possesses a relatively small capsule with a barely discernible slime layer. The wide slime layer protects virulent type III pneumococci from surface phagocytosis. Whenever the type III cells lose their broad slime layer, whether from aging of the culture, from mutation, from exposure to injurious chemicals, or from the action of type III polysaccharidase, they become susceptible to phagocytosis by the surface mechanism. Once phagocyted the type III pneumococci are promptly destroyed, even in the absence of antibodies.
已证明,五株III型肺炎球菌在血清肉汤中生长的对数期具有宽阔的荚膜黏液层。黏液层用亚甲蓝染色呈异染性,在电子显微镜下可显示为模糊的晕圈,其延伸范围远远超出了荚膜本身的表面,导致该生物体的离心物体积极大。这种外荚膜结构在体内以及含有葡萄糖和血清的营养肉汤中最易显示。随着培养物老化,它会从细胞表面消失,并且很容易被稀碱、酒精和加热去除。将覆盖有黏液的III型肺炎球菌暴露于同源抗体和III型多糖酶中发现,黏液层含有与荚膜其他部分相同的型特异性多糖。从一株产生显著黏液层的III型菌株中分离出了一个中间突变体,该突变体在血琼脂上形成小的非黏液菌落,并且具有相对较小的荚膜和几乎难以辨认的黏液层。宽阔的黏液层可保护有毒力的III型肺炎球菌免受表面吞噬作用。每当III型细胞失去其宽阔的黏液层时,无论是由于培养物老化、突变、接触有害化学物质还是III型多糖酶的作用,它们都会通过表面机制变得易于被吞噬。一旦被吞噬,III型肺炎球菌即使在没有抗体的情况下也会迅速被破坏。