Ampicillin, streptomycin and sulphamethoxazole resistant commensal E. coli 838-3B contains five plasmids that range in size from >90 kb to <2 kb. The resistance genes blaTEM (ampicillin), strA (streptomycin) and sul2 (sulphamethoxazole) transferred along with a B/O plasmid named p838B-R. However, three plasmids smaller than 7 kb were also found in transconjugants, suggesting that they could be mobilised by the B/O plasmid. The complete sequences of p838B-R and pBuzz, a small plasmid mobilised by p838B-R with 70% efficiency, were determined. p838B-R is 94,803 bp and contains an 8400 bp resistance island that includes the three antibiotic resistance genes. The p838B-R backbone contains a complete conjugative transfer region, including an oriT site upstream of nikAB that resembles the experimentally-defined oriT of R64. The 1982 bp pBuzz contains a rep gene and sites associated with replication that resemble those of pC194/pUB110 family rolling-circle plasmids. It also contains two, inversely oriented copies of an 84 bp sequence that differs from the oriT region in p838B-R at just 6 positions. These oriT-like sites likely explain the ability of pBuzz to co-transfer with the B/O plasmid using the NikB relaxase and NikA accessory protein encoded by p838B-R, i.e. pBuzz utilises relaxase-in trans mobilisation. Several rolling-circle plasmids related to pBuzz were found in the GenBank non-redundant nucleotide database. They contain diverse potential oriTs, including sequences similar to known oriTs found in conjugative plasmids of I-complex (I1, B/O, K, Z and I2), L or M types.

中文翻译：

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pBuzz：一种来自大肠埃希氏大肠杆菌的隐性滚环质粒，具有两个反向定向的oriT，并通过B / O质粒动员。

耐氨苄青霉素，链霉素和磺胺甲恶唑的普通大肠杆菌838-3B包含5个质粒，大小从> 90 kb到<2 kb。耐药基因blaTEM（氨苄青霉素），strA（链霉素）和sul2（磺胺甲恶唑）与名为p838B-R的B / O质粒一起转移。但是，在转导结合物中还发现了三个小于7 kb的质粒，表明它们可以被B / O质粒动员。确定了p838B-R和pBuzz的完整序列，p838B-R是p838B-R激活的小质粒，效率为70％。p838B-R为94,803 bp，包含一个8400 bp的抗性岛，其中包括三个抗生素抗性基因。p838B-R主链包含一个完整的共轭转移区，包括nikAB上游的一个oriT位点，类似于R64的实验定义的oriT。1982 bp的pBuzz包含一个rep基因和与复制相关的位点，类似于pC194 / pUB110家族滚环质粒的复制位点。它还包含一个84 bp序列的两个反向定向拷贝，该拷贝与p838B-R中oriT区域的仅6个位置不同。这些oriT样位点可能解释了pBuzz使用由p838B-R编码的NikB松弛酶和NikA辅助蛋白与B / O质粒共转移的能力，即pBuzz利用松弛酶进行反式动员。在GenBank非冗余核苷酸数据库中发现了与pBuzz相关的几种滚环质粒。它们包含多种潜在的oriT，包括与I型复合物（I，B / O，K，Z和I2），L或M型结合质粒中发现的已知oriT相似的序列。