Effect of chromosomal breaks induced by x-irradiation on the number of mesosomes and the cytoplasmic organization of Streptococcus faecalis.
Effect of chromosomal breaks induced by x-irradiation on the number of mesosomes and the cytoplasmic organization of Streptococcus faecalis.
复制标题
X 射线照射诱导的染色体断裂对粪链球菌介观体数量和细胞质组织的影响。
DOI：
10.1016/0022-2836(81)90040-1
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发表时间：
1981
影响因子：
5.6
通讯作者：
Higgins,ML
中科院分区：
文献类型：
--
作者：
Parks,LC;Dicker,DT;Conger,AD;Daneo-Moore,L;Higgins,ML
通过以下方法验证了一个模型，该模型解释了当细菌受到生理干扰时，通过细胞质和类核的收缩来形成介体：（1）X射线照射未固定的粪链球菌细胞，产生染色体断裂并去除附着在细胞膜上的DNA;（2）随后确定其中存在中质体的辐照细胞的数目在加入固定剂后，可以观察到中心密度变化（使用电子显微镜）和中心密度变化（使用相差显微镜）。通过在固定前将细胞暴露于高达1100 krad的剂量而获得的结果表明：（1）具有中心中质体的细胞数量与由于双链断裂而导致的DNA分子量的降低成比例地减少：（2）细胞总数（中央加外周）间质体和具有外周间质体的细胞数量都与附着在细胞膜上的DNA的去除成比例地减少（M波段）;（3）类核的组织结构更加弥散。在固定前将细胞暴露于大于1100 krad的剂量导致：（1）具有中央和外周中间体的细胞数量增加（与暴露于较低剂量的细胞相比）;（2）回归集中，这些结果表明，当细胞膜上的局部位点从与细胞壁的紧密接触被拉到细胞外时，通过细胞质内成分（如DNA）的交联固定作用而使细胞质发生聚集。该模型认为DNA和/或其他细胞质组分与膜的附着是其机制的内在部分。对比了未照射和X射线照射细胞中中心和外周中间体的形成。
A model which explains mesosome formationviaa contraction of the cytoplasm and nucleoid when bacteria are physiologically disturbed was tested by: (1) X-irradiation of unfixed cells ofStreptococcus faecalisto produce chromosomal breaks and to remove DNA attached to the cell membrane; (2) subsequent determination of the number of irradiated cells in which mesosomes (using electron microscopy) and central density changes (using phase-contrast microscopy) could be visualized after fixative was added. Results obtained by exposure of cells to doses up to 1100 krads before fixation indicated that: (1) the number of cells with central mesosomes was reduced proportional to the decrease in the molecular weight of the DNA due to double-strand breaks: (2) the number of cells with total (central plus peripheral) mesosomes and the number of cells with peripheral mesosomes were both reduced proportional to the removal of DNA attached to the cell membrane (M band); (3) the nucleoid became more diffusely organized. Exposure of cells to doses greater than 1100 krads before fixation resulted in: (1) an increase in the number of cells with central and peripheral mesosomes (compared to cells exposed to lower dosages); (2) a return to the centralized, dense nucleoid seen in unirradiated cells.These results suggest that mesosomes are formed when localized sites on the cell membrane are pulled from close contact with the cell wall into the cytoplasm by the action of a cross-linking fixativeviathe aggregation of intracytoplasmic components such as DNA. This model considers the attachment of DNA and/or other cytoplasmic components to the membrane as an intrinsic part of its mechanism. The formation of central and peripheral mesosomes in unirradiated and X-irradiated cells are contrasted.