Kozloff L M, Chapman V, DeLong S
Prog Clin Biol Res. 1981;64:253-69.
A newly isolated bacteriophage, Erh 1, for Erwinia herbicola, has been characterized. This virulent phage has been found to have an elongated rod-like head and a short complex tail structure. One major protein and 5 minor proteins have been identified as phage components. The head structure was found to be transparent, flexible and could be twisted or flattened by various treatments. The DNA, isolated from highly purified phage particles, was linear, double-stranded, had a G-C content of 46-47% and displayed two unique features. (1) The isolated phage DNA molecules were highly heterogeneous in contour lengths; the most prevalent molecules had a length of 6-12 mu, but molecules have been measured with lengths ranging from 2.3 mu to 37 mu. (2) One or two long single-stranded regions, "gaps," ranging in length from 0.3 to 3.1 mu with an average length of 1.4 +/- 0.7 mu, were found in about 25% of the phage DNA molecules. Upon density gradient centrifugation of p32 labeled phage, it was found that most of the DNA was contained in apparently noninfectious, defective particles, with densities ranging from 1.34 to 1.41 while most of the infectious particles were found in fractions of density of 1.44 +/- 0.02. When used to multiply infect cells, the lower density particles were able to complement each other and form infectious centers. Further, it was found that infectious particles themselves were heterogeneous and had sedimentation constants varying from 600 S to 1400 S. From the distribution of DNA sizes in these particles, the variations in sedimentation behavior, and the flexibility of the head structure of most particles, it appears that the head structure is formed first and then the DNA is packed inefficiently into this head structure. Apparently, most phage particles are only partly filled and do not contain a complete genome while a few others may contain a large amount of redundant viral DNA.
一种新分离出的针对草生欧文氏菌的噬菌体Erh 1已得到鉴定。这种烈性噬菌体具有细长的杆状头部和短而复杂的尾部结构。已鉴定出一种主要蛋白质和5种次要蛋白质为噬菌体成分。发现头部结构是透明的、可弯曲的，并且可以通过各种处理使其扭曲或变平。从高度纯化的噬菌体颗粒中分离出的DNA是线性双链的，G-C含量为46-47%，并表现出两个独特特征。(1)分离出的噬菌体DNA分子在轮廓长度上高度异质；最常见的分子长度为6-12微米，但已测量到的分子长度范围为2.3微米至37微米。(2)在约25%的噬菌体DNA分子中发现一个或两个长的单链区域，即“缺口”，长度从0.3至3.1微米不等，平均长度为1.4±0.7微米。对用p32标记的噬菌体进行密度梯度离心时，发现大部分DNA存在于明显无感染性的缺陷颗粒中，密度范围为1.34至1.41，而大部分感染性颗粒存在于密度为1.44±0.02的组分中。当用于多重感染细胞时，低密度颗粒能够相互互补并形成感染中心。此外，发现感染性颗粒本身也是异质的，沉降常数在600 S至1400 S之间变化。从这些颗粒中DNA大小的分布、沉降行为的变化以及大多数颗粒头部结构的柔韧性来看，似乎头部结构首先形成，然后DNA低效地包装到这个头部结构中。显然，大多数噬菌体颗粒只是部分填充，不包含完整的基因组，而其他一些颗粒可能包含大量冗余的病毒DNA。
