首页> 外文OA文献 >Labeling of binding sites for beta 2-microglobulin (beta 2m) on nonfibrillar surface structures of mutans streptococci by immunogold and beta 2m-gold electron microscopy.
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Labeling of binding sites for beta 2-microglobulin (beta 2m) on nonfibrillar surface structures of mutans streptococci by immunogold and beta 2m-gold electron microscopy.

机译:通过免疫金和β2m-金电子显微镜对变形链球菌非原纤维表面结构上β2-微球蛋白(β2m)的结合位点进行标记。

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摘要

As little detail is known about the surface structure of streptococci in the mutans group and the relationship of surface structure to host ligand-binding functions, the twofold purpose of this investigation was to examine in detail, by a range of electron microscopic techniques, the surface structures of streptococci in the different species of the mutans group and to investigate the distribution of beta 2-microglobulin (beta 2m)-binding sites on such structures. Strains representing Streptococcus mutans, S. cricetus, S. rattus, S. sobrinus, and four fresh isolates were studied by shadowcasting and histochemical staining of whole-mounted cells as well as by ultrathin and thick sectioning of embedded specimens. beta 2m-binding site distribution was visualized by indirect immunogold electron microscopy and by direct bacterial binding of beta 2m-conjugated gold probes. Shadowcast preparations revealed binding of gold probes to the cell surface of known beta 2m-binding strains but not to their polar fibrillar appendages. These long fibrils, common to all strains, were trypsin and sonication sensitive and stained with lead citrate but not with uranyl acetate or ruthenium red. More gold particles were bound by the indirect technique. For grid-mounted bacteria, the gold was mostly bound in clusters at the periphery of the cells. When gold probes were reacted in suspension with bacteria before mounting onto grids, a more even distribution of the gold was seen, but the bacteria were aggregated. Heating the bacteria eliminated beta 2m-gold binding but had no effect on the morphology of the fibrils. Thick sections of embedded bacteria prereacted with beta 2m-conjugated gold probes were analyzed by stereo imaging. A wispy, uranyl acetate-stained fuzzy layer, distinct from the fibrils seen by shadowcasting and extending up to one cell diameter from the cell wall, contained the gold probes. These findings introduce a concept that binding sites for some salivary ligands on mutans streptococci may be clustered on very delicate, nonfibrillar structures extending much further from the cell wall than previously appreciated. As for beta 2m, which composes part of the human histocompatibility antigens, part of the bacterial surface would be coated at a distance from its body with a protein not necessarily recognized as foreign by the host.
机译:由于对变形链球菌中链球菌的表面结构及其与宿主配体结合功能之间关系的了解很少,该研究的双重目的是通过一系列电子显微镜技术详细检查表面。变形链球菌的不同物种中链球菌的结构,并研究β2-微球蛋白(β2m)结合位点在此类结构上的分布。通过影射和整个固定细胞的组织化学染色,以及通过超薄和厚切片的嵌入式标本,研究了代表变形链球菌,S。cricetus,S。rattus,S。sobrinus和四个新鲜分离株的菌株。 β2m结合位点的分布通过间接免疫金电子显微镜和结合β2m的金探针的直接细菌结合可视化。暗影制剂显示金探针与已知的β2m结合菌株的细胞表面结合,但不与它们的极原纤维附肢结合。这些长原纤维对所有菌株都通用,对胰蛋白酶和超声敏感,并用柠檬酸铅染色,但不用乙酸铀酰或钌红染色。间接技术束缚了更多的金颗粒。对于安装在网格上的细菌,金大多结合在细胞外围的簇中。当金探针在悬浮于网格上之前与细菌在悬浮液中反应时,金的分布更加均匀,但细菌却聚集了。加热细菌消除了β2m-金的结合,但对原纤维的形态没有影响。通过立体成像分析了与β2m共轭金探针预反应的包埋细菌的厚切片。一个薄薄的,醋酸铀酰染色的模糊层,不同于金丝,可以通过阴影投射看到,并从细胞壁延伸到一个细胞直径,其中包含金探针。这些发现引入了这样的概念,即变形链球菌上某些唾液配体的结合位点可能聚集在非常细腻的,非原纤维结构上,该结构比细胞壁更远地延伸。至于构成人类组织相容性抗原的一部分的beta 2m,细菌表面的一部分将在距其身体一定距离处被一种不一定被宿主识别为异物的蛋白质覆盖。

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