Saunders V A, Saunders J R, Bennett P M
J Bacteriol. 1976 Mar;125(3):1180-7. doi: 10.1128/jb.125.3.1180-1187.1976.
Three covalently closed circular species of extrachromosomal deoxyribonucleic acid have been identified by electron microscopic analysis in strains of Rhodopseudomonas spheroides. The weights of these plasmids, as determined from contour length, are about 75 X 10(6), 66 X 10(6), and 28 X 10(6) daltons for both aerobically grown and photosynthetically grown R. spheroides strain 2.4.1 (NRS) and for the photosynthetically incompetent strain V-2 (obtained by N-methyl-N-nitro-N'nitrosoguanidine mutagenesis) and 74 X 10(6), 66 X 10(6) and 34 X 10(6) daltons for a second photosynthetically incompetent strain, SLS I (obtained by incubating strain 2.4.1 [NRS] in medium containing sodium lauryl sulfate). Buoyant densities uere found to be 1.717 g/cm3 (58% guanine plus cytosine) for the plasmids of 66 X 10(6), 28 X 10(6), and 34 X 10(6) daltons in weight and 1.724 g/cm3 (65% guanine plus cytosine) for those weighing about 75 X 10(6) daltons. Possible functions of these plasmids are discussed.
通过电子显微镜分析，在球形红假单胞菌菌株中鉴定出了三种共价闭合环状的染色体外脱氧核糖核酸。对于需氧生长和光合生长的球形红假单胞菌菌株2.4.1（NRS）以及光合缺陷型菌株V-2（通过N-甲基-N-硝基-N'-亚硝基胍诱变获得），这些质粒的重量（由轮廓长度确定）分别约为75×10⁶、66×10⁶和28×10⁶道尔顿；对于第二个光合缺陷型菌株SLS I（通过将菌株2.4.1 [NRS]在含有十二烷基硫酸钠的培养基中培养获得），其重量分别为74×10⁶、66×10⁶和34×10⁶道尔顿。发现重量为66×10⁶、28×10⁶和34×10⁶道尔顿的质粒的浮力密度为1.717 g/cm³（58%鸟嘌呤加胞嘧啶），重量约为75×10⁶道尔顿的质粒的浮力密度为1.724 g/cm³（65%鸟嘌呤加胞嘧啶）。文中讨论了这些质粒可能的功能。
