Solaiman D K, Somkuti G A
U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, Philadelphia, Pennsylvania 19118.
Plasmid. 1993 Jul;30(1):67-78. doi: 10.1006/plas.1993.1034.
pER8 (2.2 kb), a native plasmid of Streptococcus thermophilus ST108, was used to develop pMEU-series shuttle vectors. In addition to the replication function of the pER8, these vectors contain origin of replication and beta-lactamase gene (bla) of Escherichia coli vector pUC18/19, the cat gene of pC194, and the pPV141-borne erm determinant of Staphylococcus hyicus ssp. chromogenes 3688. pMEU5a, pMEU5b, pMEU6a, and pMEU6b (all 5.7 kb in size) contain bla and erm markers, are capable of transforming E. coli and S. thermophilus at frequencies in the order of 10(5)-10(6) and 10(3) colony forming units (CFU)/microgram DNA, respectively, and are highly stable in the two host systems. pMEU9 and pMEU10 (both 6.9 kb) contain the cat marker in addition to the DNA elements found in pMEU5-6. These plasmids are also highly effective in transforming E. coli (at ca. 6 x 10(5) CFU/microgram DNA) and S. thermophilus (ca. 10(3) CFU/microgram DNA). Although expression of the resistance markers is not completely consistent, pMEU9 and pMEU10 remain important shuttle vectors for clonal selection by an insertional inactivation method.
pER8（2.2 kb）是嗜热链球菌ST108的天然质粒，用于构建pMEU系列穿梭载体。除了pER8的复制功能外，这些载体还包含大肠杆菌载体pUC18/19的复制起点和β-内酰胺酶基因（bla）、pC194的cat基因以及来自产色葡萄球菌亚种3688的pPV141携带的erm决定簇。pMEU5a、pMEU5b、pMEU6a和pMEU6b（大小均为5.7 kb）含有bla和erm标记，能够分别以10⁵ - 10⁶和10³集落形成单位（CFU）/微克DNA的频率转化大肠杆菌和嗜热链球菌，并且在这两种宿主系统中高度稳定。pMEU9和pMEU10（均为6.9 kb）除了含有pMEU5 - 6中的DNA元件外，还含有cat标记。这些质粒在转化大肠杆菌（约6×10⁵ CFU/微克DNA）和嗜热链球菌（约10³ CFU/微克DNA）方面也非常有效。尽管抗性标记的表达并不完全一致，但pMEU9和pMEU10仍然是通过插入失活法进行克隆选择的重要穿梭载体。
