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pBuzz:来自共生大肠杆菌的隐蔽滚环质粒具有两个反向定向的oriTs,并由B / O质粒动员

发布者:抗性基因网 时间:2018-11-26 浏览量:904

摘要

氨苄青霉素,链霉素和磺胺甲氧嘧啶抗性共生大肠杆菌838-3B含有5种质粒,大小范围从> 90kb到<2kb。抗性基因blaTEM(氨苄青霉素),strA(链霉素)和sul2(磺胺甲基异恶唑)与名为p838B-R的B / O质粒一起转移。然而,在转接合子中也发现了三个小于7kb的质粒,表明它们可以被B / O质粒动员。测定了p838B-R和pBuzz的完整序列,p838B是由p838B-R以70%的效率动员的小质粒。 p838B-R为94,803bp,含有一个8400bp的抗性岛,其中包含三种抗生素抗性基因。 p838B-R骨架含有完整的接合转移区,包括nikAB上游的oriT位点,其类似于实验定义的R64的oriT。 1982bp pBuzz含有rep基因和与复制相关的位点,类似于pC194 / pUB110家族滚环质粒。它还包含两个反向定向的84bp序列拷贝,它与p838B-R中仅有6个位置的oriT区域不同。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 - 反式动员。在GenBank非冗余核苷酸数据库中发现了几个与pBuzz相关的滚环质粒。它们含有多种潜在的oriT,包括与I-复合物(I1,B / O,K,Z和I2),L或M型的接合质粒中发现的已知oriTs相似的序列。


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.


https://www.ncbi.nlm.nih.gov/pubmed/30468749