Rode C K, Melkerson-Watson L J, Johnson A T, Bloch C A
Department of Pediatrics and Communicable Diseases, University of Michigan School of Medicine, Ann Arbor 49109-0656, USA.
Infect Immun. 1999 Jan;67(1):230-6. doi: 10.1128/IAI.67.1.230-236.1999.
The Escherichia coli genome varies in size from 4.5 to 5.5 Mb. It is unclear whether this variation may be distributed finely throughout the genome or is concentrated at just a few chromosomal loci or on plasmids. Further, the functional correlates of size variation in different genome copies are largely unexplored. We carried out comparative macrorestriction mapping using rare-restriction-site alleles (made with the Tn10dRCP2 family of elements, containing the NotI, BlnI, I-CeuI, and ultra-rare-cutting I-SceI sites) among the chromosomes of laboratory E. coli K-12, newborn-sepsis-associated E. coli RS218, and uropathogenic E. coli J96. These comparisons showed just a few large accessory chromosomal segments accounting for nearly all strain-to-strain size differences. Of 10 sepsis-associated and urovirulence genes, previously isolated from the two pathogens by scoring for function, all were colocalized exclusively with one or more of the accessory chromosomal segments. The accessory chromosomal segments detected in the pathogenic strains from physical, macrorestriction comparisons may be a source of new virulence genes, not yet isolated by function.
大肠杆菌基因组大小在4.5至5.5兆碱基之间变化。目前尚不清楚这种变化是均匀分布于整个基因组，还是集中在少数几个染色体位点或质粒上。此外，不同基因组拷贝中大小变化的功能相关性在很大程度上尚未得到探索。我们利用稀有限制性位点等位基因（由Tn10dRCP2元件家族构建，包含NotI、BlnI、I-CeuI和极稀有切割的I-SceI位点），对实验室大肠杆菌K-12、新生儿败血症相关大肠杆菌RS218和尿路致病性大肠杆菌J96的染色体进行了比较宏观限制性图谱分析。这些比较表明，只有少数几个大的辅助染色体片段几乎占了所有菌株间大小差异。在之前通过功能筛选从这两种病原体中分离出的10个败血症相关基因和尿路致病基因中，所有基因都仅与一个或多个辅助染色体片段共定位。通过物理宏观限制性比较在致病菌株中检测到的辅助染色体片段可能是新毒力基因的来源，尚未通过功能分离出来。
