Orndorff P E, Dworkin M
J Bacteriol. 1980 Feb;141(2):914-27. doi: 10.1128/jb.141.2.914-927.1980.
We have developed methods for separating the cytoplasmic and outer membranes of vegetative cells of Myxococcus xanthus. The total membrane fraction from ethylenediaminetetraacetic acid-lysozyme-treated cells was resolved into three major fractions by isopycnic density centrifugation. Between 85 and 90% of the succinate dehydrogenase and cyanide-sensitive reduced nicotinamide adenine dinucleotide oxidase activity was found in the first (I) fraction (rho = 1.221 g/ml) and 80% of the membrane-associated 2-keto-3-deoxyoctonate was found in the third (III) fraction (rho = 1.166 g/ml). The middle (II) fraction (rho = 1.185 g/ml) appeared to be a hybrid membrane fraction and contained roughly 10 to 20% of the activity of the enzyme markers and 2-keto-3-deoxyoctonate. No significant amounts of deoxyribonucleic acid or ribonucleic acid were present in the three isolated fractions, although 26% of the total cellular deoxyribonucleic acid and 3% of the total ribonucleic acid were recovered with the total membrane fraction. Phosphatidylethanolamine made up the bulk (60 to 70%) of the phospholipids in the membrane fractions. However, virtually all of the phosphatidylserine and cardiolipin were found in fraction I. Fraction III appeared to contain elevated amounts of lysophospholipids and contained almost three times the amount of total phospholipid as compared with fraction I. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis resolved approximately 40 polypeptides in the total membrane fraction. Two-thirds of these polypeptides were enriched in fraction I, and the remainder was enriched in fraction III. Fraction II contained a banding pattern similar to the total membrane fraction. Electron microscopy revealed that vegetative cells of M. xanthus possessed an envelope similar to that of other gram-negative bacteria; however, the vesicular appearance of the isolated membranes was somewhat different from those reported for Escherichia coli and Salmonella typhimurium. The atypically low bouyant density of the outer membrane of M. xanthus is discussed with regard to the high phospholipid content of the outer membrane.
我们已开发出分离黄色粘球菌营养细胞的细胞质膜和外膜的方法。经乙二胺四乙酸 - 溶菌酶处理的细胞的总膜部分通过等密度离心被分离成三个主要部分。在第一部分（I）（密度 = 1.221 g/ml）中发现了85%至90%的琥珀酸脱氢酶和对氰化物敏感的还原型烟酰胺腺嘌呤二核苷酸氧化酶活性，在第三部分（III）（密度 = 1.166 g/ml）中发现了80%的与膜相关的2 - 酮 - 3 - 脱氧辛酸。中间部分（II）（密度 = 1.185 g/ml）似乎是一个混合膜部分，含有大约10%至20%的酶标记物和2 - 酮 - 3 - 脱氧辛酸活性。在这三个分离部分中未发现大量的脱氧核糖核酸或核糖核酸，尽管在总膜部分中回收了26%的总细胞脱氧核糖核酸和3%的总核糖核酸。磷脂酰乙醇胺占膜部分中磷脂的大部分（60%至70%）。然而，几乎所有的磷脂酰丝氨酸和心磷脂都在部分I中发现。部分III似乎含有较高量的溶血磷脂，其总磷脂含量几乎是部分I的三倍。十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳在总膜部分中分离出大约40种多肽。其中三分之二的多肽在部分I中富集，其余的在部分III中富集。部分II包含与总膜部分相似的条带模式。电子显微镜显示，黄色粘球菌的营养细胞具有与其他革兰氏阴性细菌相似的包膜；然而，分离膜的囊泡外观与大肠杆菌和鼠伤寒沙门氏菌报道的有所不同。关于黄色粘球菌外膜异常低的浮力密度，讨论了外膜中高磷脂含量的问题。
