State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, 214122, China; Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China.
Department of Biological Engineering, College of Life Science, Yantai University, Yantai, 264005, China.
Microbiol Res. 2020 Oct;239:126527. doi: 10.1016/j.micres.2020.126527. Epub 2020 Jun 18.
Lipopolysaccharide and colanic acid are important forms of exopolysaccharides located on the cell surface of Escherichia coli, but their interrelation with the cell stress response is not well understood. In this study, nine mutant strains with different structures of lipopolysaccharide were constructed from E. coli MG1655 by deletion of a single gene or multiple genes. All mutant strains did not produce colanic acid when grown in LB medium, but six of them could produce colanic acid when grown either in M9 medium in which glucose is the sole carbon source or in LB medium supplemented with glucose. The results indicate that colanic acid production in E. coli is dependent on both lipopolysaccharide structure and glucose availability. However, transcriptional analysis showed that 20 genes related to the colanic acid biosynthesis and the key gene rcsA in the Rcs system were all transcriptionally up-regulated in all of the nine mutant strains no matter they were grown in M9 or LB medium. This suggests that the availability of some nucleotide-sugar precursors shared by the biosynthesis of lipopolysaccharide and colanic acid might play a major role in colanic acid production in E. coli. Lipopolysaccharide pathway might have a huge priority to colanic acid pathway to use the common precursors; therefore, the colanic acid is not produced in MG1655 and the nine mutants when grown in LB medium. In the six mutant strains that can produce colanic acid in the glucose rich media, the common precursors might be abundant because they were not needed for synthesizing the mutant lipopolysaccharide.
脂多糖和菌毛酸是大肠杆菌细胞表面重要的胞外多糖形式，但它们与细胞应激反应的关系尚不清楚。在这项研究中，通过缺失单个或多个基因，从大肠杆菌 MG1655 中构建了 9 株具有不同脂多糖结构的突变株。所有突变株在 LB 培养基中生长时都不产生菌毛酸，但其中 6 株在以葡萄糖为唯一碳源的 M9 培养基或补充葡萄糖的 LB 培养基中生长时可以产生菌毛酸。结果表明，大肠杆菌中菌毛酸的产生既依赖于脂多糖结构，也依赖于葡萄糖的可用性。然而，转录分析表明，在所有 9 株突变株中，与菌毛酸生物合成相关的 20 个基因和 Rcs 系统中的关键基因 rcsA 均转录上调，无论它们是在 M9 培养基还是 LB 培养基中生长。这表明，用于合成脂多糖和菌毛酸的一些核苷酸糖前体的可用性可能在大肠杆菌中菌毛酸的产生中起主要作用。脂多糖途径可能优先于菌毛酸途径来利用共同的前体；因此，当在 LB 培养基中生长时，MG1655 和 9 株突变株都不产生菌毛酸。在 6 株能够在富含葡萄糖的培养基中产生菌毛酸的突变株中，由于不需要用于合成突变脂多糖，共同的前体可能很丰富。
