Structure And Stabilization Of The Bacterial Nucleoid

细菌的DNA定位在每个细胞中的几个紧凑体中，称为类核。控制压实提供了一种几乎未探索的与细菌生长相互作用并潜在地控制细菌生长的方法。 我们以前已经开发了定量程序来测定大肠杆菌中参与类核压缩的因素。这些因素之一，已知30年，但从未确定，其特点是RNA酶敏感性。通过使用新的测定方法，这种RNA酶敏感组分已被鉴定为类核DNA和细胞包膜之间共翻译插入键的核糖体连接。 在暴露于E.大肠杆菌对氯霉素的敏感性以及在其他几种条件下的敏感性特别令人感兴趣。Cm-类核对变性非常稳定，并且似乎是由正常类核通过相对直接和有效的可逆转化形成的，这为了解正常类核的未知结构提供了潜在的见解。尽管另一个实验室曾多次提出过cm-类核的空心球模型，但该模型无法解释相当一部分cm-类核在光学显微镜下的外观。本文提出了一种新的CM-类核的弯曲环形结构，它可以使以前不一致的观测合理化。

The DNA of bacteria is localized in a few compact bodies per cell known as nucleoids. Control of compaction offers a virtually unexplored means of interacting with and potentially controlling bacterial growth. We have previously developed quantitative procedures to assay factors that are involved in nucleoid compaction in Escherichia coli. One of these factors, known for 30 years but never identified, is characterized by its RNase-sensitivity. By use of the new assay procedures, this RNase-sensitive component has been identified as the ribosomal link in cotranslational insertion linkages between the nucleoidal DNA and the cell envelope. The rounded nucleoids ("cm-nucleoids)that are formed upon exposure of E. coli to chloramphenicol, as well as under several other conditions, are of particular interest. Cm-nucleoids are extraordinarily stable to denaturation and appear to be formed by a relatively direct and efficiently reversible conversion from normal nucleoids, offering potential insights into the unknown structure of the normal nucleoid. Although a hollow spherical model had been repeatedly presented for cm-nucleoids by another laboratory, that model is unable to account for the light microscope appearance of a significant fraction of cm-nucleoids. A new type of curved toroidal structure is proposed for cm-nucleoids which can rationalize the previously discordant observations.