PDF(Pubmed)
Abstract：
Most Escherichia coli isolates from humans do not utilize D-sucrose as a substrate for fermentation or growth. Previous work has shown that the Csc pathway allows some E. coli to utilize sucrose for slow growth, and this pathway has been engineered in E. coli W strains to enhance use of sucrose as a feedstock for industrial applications. An alternative sucrose utilization pathway, Scr, was first identified in Klebsiella pneumoniae and has been reported in some E. coli and Salmonella enterica isolates. We show here that the Scr pathway is native to an important subset of E. coli phylogroup B2 lineages that lack the Csc pathway but grow rapidly on sucrose. Laboratory E. coli strains derived from MG1655 (phylogroup A, ST10) are unable to utilize sucrose and lack the scr and csc genes, but a recombinant plasmid-borne scr locus enables rapid growth on and fermentation of sucrose. Genome analyses of Enterobacteriaceae indicate that the scr locus is widespread in other Enterobacteriaceae; including Enterobacter and Klebsiella species, and some Citrobacter and Proteus species. In contrast, the Csc pathway is limited mostly to E. coli, some Shigella species (in which csc loci are rendered non-functional by various mutations), and Citrobacter freundii. The more efficient Scr pathway likely has greater potential than the Csc pathway for bioindustrial applications of E. coli and other Enterobacteriaceae using sucrose as a feedstock.
摘要：
大多数来自人类的大肠杆菌分离物不利用D-蔗糖作为发酵或生长的底物。以前的工作表明，Csc途径允许一些大肠杆菌利用蔗糖进行缓慢生长，并且该途径已经在大肠杆菌W菌株中被工程化以增强蔗糖作为工业应用的原料的用途。一种替代的蔗糖利用途径，Scr,首次在肺炎克雷伯菌中鉴定，并已在一些大肠杆菌和沙门氏菌分离株中报道。我们在这里表明，Scr途径是大肠杆菌系统系B2谱系的一个重要子集的天然，这些谱系缺乏Csc途径，但在蔗糖上快速生长。实验室大肠杆菌菌株来自MG1655(系统群A，ST10)无法利用蔗糖，缺乏scr和csc基因，但是重组质粒携带的scr基因座可以使蔗糖快速生长和发酵。肠杆菌科的基因组分析表明，scr基因座广泛存在于其他肠杆菌科;包括肠杆菌和克雷伯氏菌属。还有一些柠檬酸杆菌和变形杆菌.相比之下,Csc途径主要局限于大肠杆菌,一些志贺氏菌（其中csc基因座通过各种突变变得无功能），和freundii柠檬酸杆菌.对于使用蔗糖作为原料的大肠杆菌和其他肠杆菌科的生物工业应用,更有效的Scr途径可能比Csc途径具有更大的潜力。
