Faure D, Frederick R, Włoch D, Portier P, Blot M, Adams J
Plasticité et Expression des Génomes Microbiens, CNRS FRE2383, Université Joseph-Fourier, Grenoble, France.
J Bacteriol. 2004 Oct;186(19):6437-42. doi: 10.1128/JB.186.19.6437-6442.2004.
Genomic scans of clones isolated from long-term stab cultures of Escherichia coli K-12 showed the loss of two large segments of the genome, with each lost segment being approximately 20 kb long. A detailed analysis of one of the deletions, located between 5.4 and 5.9 min, revealed that similar deletions had arisen in several other stab cultures. All deletions of this type exhibited a right terminus ending precisely at an IS5A element and a left terminus that varied over an approximately 5-kb range but was bordered in all but two cases by sequences belonging to the preferred consensus target sequence for IS5, YTAR. The ubiquity of such deletions in independent stab cultures and the increase in their frequency over time argue that they have a selective advantage. It is speculated that the loss of the crl locus is responsible for the selective advantage of the deletions.
对从大肠杆菌K-12长期穿刺培养物中分离出的克隆进行基因组扫描，结果显示基因组的两个大片段缺失，每个缺失片段长度约为20 kb。对位于5.4至5.9分钟之间的其中一个缺失进行详细分析后发现，其他几个穿刺培养物中也出现了类似的缺失。所有这种类型的缺失都表现出一个精确终止于IS5A元件的右端点和一个在约5 kb范围内变化的左端点，但除了两例之外，在所有情况下其边界都由属于IS5的首选共有靶序列YTAR的序列构成。这种缺失在独立的穿刺培养物中普遍存在且其频率随时间增加，这表明它们具有选择优势。据推测，crl基因座的缺失是这些缺失具有选择优势的原因。
