Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada.
Can J Microbiol. 2009 Nov;55(11):1229-39. doi: 10.1139/w09-079.
Two uncharacterized small cryptic plasmids (SCPs) were isolated from enteropathogenic Escherichia coli strain E2348/69. Genomic DNA sequence analysis of both SCPs indicated that the smaller plasmid, p5217, encoded several mobilization genes, whereas the larger plasmid, p6148, encoded several putative antibiotic resistance determinants. Complementation analysis showed that p6148 encodes functional streptomycin resistance genes but, owing to the presence of several frameshift mutations, a nonfunctional sulfonamide resistance determinant. A plasmid similar to p6148 has previously been shown to confer a slight growth advantage on E. coli. However, we were unable to observe any significant growth advantage in different E. coli strains transformed with p6148. The p6148 DNA sequence is homologous in sequence and arrangement to DNA from other plasmid families, including large conjugative plasmids and SXT integrative and conjugative elements. This study suggests that gene clusters of the sul2-strAB antibiotic resistance genes are widespread and highly transferable, owing to their presence in a wide variety of mobile genetic elements.
从肠致病性大肠杆菌 E2348/69 株中分离得到两个未被描述的小型隐秘质粒（SCP）。对两个 SCP 的基因组 DNA 序列分析表明，较小的质粒 p5217 编码了几个移动基因，而较大的质粒 p6148 编码了几个推定的抗生素抗性决定簇。互补分析表明，p6148 编码功能性链霉素抗性基因，但由于存在几个移码突变，导致磺胺类药物抗性决定簇失活。以前的研究表明，类似 p6148 的质粒可赋予大肠杆菌轻微的生长优势。然而，我们无法观察到用 p6148 转化的不同大肠杆菌菌株有任何明显的生长优势。p6148 的 DNA 序列在序列和排列上与其他质粒家族的 DNA 同源，包括大型接合质粒和 SXT 整合和接合元件。本研究表明，sul2-strAB 抗生素抗性基因簇由于存在于多种可移动遗传元件中而广泛存在且高度可转移。
