Department of Crop Sciences, University of Illinois, Urbana, Illinois, United States of America.
PLoS One. 2011;6(9):e25293. doi: 10.1371/journal.pone.0025293. Epub 2011 Sep 27.
YbjN, encoding an enterobacteria-specific protein, is a multicopy suppressor of temperature sensitivity in the ts9 mutant strain of Escherichia coli. In this study, we further explored the role(s) of ybjN. First, we demonstrated that the ybjN transcript was about 10-fold lower in the ts9 strain compared to that of E. coli strain BW25113 (BW). Introduction of multiple copies of ybjN in the ts9 strain resulted in over-expression of ybjN by about 10-fold as compared to that of BW. These results suggested that temperature sensitivity of the ts9 mutant of E. coli may be related to expression levels of ybjN. Characterization of E. coli ybjN mutant revealed that ybjN mutation resulted in pleiotropic phenotypes, including increased motility, fimbriation (auto-aggregation), exopolysaccharide production, and biofilm formation. In contrast, over-expression of ybjN (in terms of multiple copies) resulted in reduced motility, fimbriation, exopolysaccharide production, biofilm formation and acid resistance. In addition, our results indicate that a ybjN-homolog gene from Erwinia amylovora, a plant enterobacterial pathogen, is functionally conserved with that of E. coli, suggesting similar evolution of the YbjN family proteins in enterobacteria. A microarray study revealed that the expression level of ybjN was inversely correlated with the expression of flagellar, fimbrial and acid resistance genes. Over-expression of ybjN significantly down-regulated genes involved in citric acid cycle, glycolysis, the glyoxylate shunt, oxidative phosphorylation, amino acid and nucleotide metabolism. Furthermore, over-expression of ybjN up-regulated toxin-antitoxin modules, the SOS response pathway, cold shock and starvation induced transporter genes. Collectively, these results suggest that YbjN may play important roles in regulating bacterial multicellular behavior, metabolism, and survival under stress conditions in E. coli. These results also suggest that ybjN over-expression-related temperature rescue of the ts9 mutant may be due to down-regulation of metabolic activity and activation of stress response genes in the ts9 mutant.
YbjN 编码一种特定于肠杆菌的蛋白质，是大肠杆菌 ts9 突变株温度敏感性的多拷贝抑制子。在本研究中，我们进一步探讨了 ybjN 的作用。首先，我们证明与 BW25113（BW）相比，ts9 菌株中的 ybjN 转录物约低 10 倍。在 ts9 菌株中引入多个 ybjN 拷贝，导致 ybjN 的表达比 BW 高约 10 倍。这些结果表明，大肠杆菌 ts9 突变体的温度敏感性可能与 ybjN 的表达水平有关。E. coli ybjN 突变体的表征表明，ybjN 突变导致表型多效性，包括运动性增强、纤毛形成（自动聚集）、胞外多糖产生和生物膜形成。相比之下，ybjN 的过度表达（以多个拷贝计）导致运动性、纤毛形成、胞外多糖产生、生物膜形成和耐酸性降低。此外，我们的结果表明，植物肠杆菌病原体埃希氏菌属的 ybjN 同源基因在功能上与大肠杆菌的同源，这表明肠杆菌中 YbjN 家族蛋白的进化相似。微阵列研究表明，ybjN 的表达水平与鞭毛、纤毛和耐酸基因的表达呈负相关。ybjN 的过度表达显著下调了柠檬酸循环、糖酵解、乙醛酸支路、氧化磷酸化、氨基酸和核苷酸代谢相关基因。此外，ybjN 的过度表达上调了毒素-抗毒素模块、SOS 反应途径、冷休克和饥饿诱导的转运体基因。总的来说，这些结果表明 YbjN 可能在调节细菌的多细胞行为、代谢和应激条件下的生存方面发挥重要作用。这些结果还表明，ybjN 过表达相关的 ts9 突变体温度拯救可能是由于代谢活性下调和 ts9 突变体中应激反应基因的激活。
