Institute of Molecular Medicine and Biological Technology, National Chiao Tung University, Hsin Chu, Taiwan, Republic of China.
PLoS One. 2013 Jul 23;8(7):e66740. doi: 10.1371/journal.pone.0066740. Print 2013.
This study shows that the expression of yjcC, an in vivo expression (IVE) gene, and the stress response regulatory genes soxR, soxS, and rpoS are paraquat inducible in Klebsiella pneumoniae CG43. The deletion of rpoS or soxRS decreased yjcC expression, implying an RpoS- or SoxRS-dependent control. After paraquat or H2O2 treatment, the deletion of yjcC reduced bacterial survival. These effects could be complemented by introducing the ΔyjcC mutant with the YjcC-expression plasmid pJR1. The recombinant protein containing only the YjcC-EAL domain exhibited phosphodiesterase (PDE) activity; overexpression of yjcC has lower levels of cyclic di-GMP. The yjcC deletion mutant also exhibited increased reactive oxygen species (ROS) formation, oxidation damage, and oxidative stress scavenging activity. In addition, the yjcC deletion reduced capsular polysaccharide production in the bacteria, but increased the LD50 in mice, biofilm formation, and type 3 fimbriae major pilin MrkA production. Finally, a comparative transcriptome analysis showed 34 upregulated and 29 downregulated genes with the increased production of YjcC. The activated gene products include glutaredoxin I, thioredoxin, heat shock proteins, chaperone, and MrkHI, and proteins for energy metabolism (transporters, cell surface structure, and transcriptional regulation). In conclusion, the results of this study suggest that YjcC positively regulates the oxidative stress response and mouse virulence but negatively affects the biofilm formation and type 3 fimbriae expression by altering the c-di-GMP levels after receiving oxidative stress signaling inputs.
本研究表明，活体表达（IVE）基因 yjcC 及其应激反应调节基因 soxR、soxS 和 rpoS 的表达在肺炎克雷伯菌 CG43 中受百草枯诱导。rpoS 或 soxRS 的缺失降低了 yjcC 的表达，表明存在 RpoS 或 SoxRS 依赖性调控。在百草枯或 H2O2 处理后，yjcC 的缺失降低了细菌的存活率。这些效应可以通过引入含有 YjcC-EAL 结构域的表达质粒 pJR1 来补偿 ΔyjcC 突变体。仅含有 YjcC-EAL 结构域的重组蛋白表现出磷酸二酯酶（PDE）活性；yjcC 的过表达导致环二鸟苷酸（c-di-GMP）水平降低。yjcC 缺失突变体还表现出活性氧（ROS）形成增加、氧化损伤和氧化应激清除活性降低。此外，yjcC 缺失减少了细菌荚膜多糖的产生，但增加了 LD50 小鼠、生物膜形成和 III 型菌毛主要 pilin MrkA 的产生。最后，比较转录组分析显示，随着 YjcC 的产生增加，有 34 个上调基因和 29 个下调基因。激活的基因产物包括谷氧还蛋白 I、硫氧还蛋白、热休克蛋白、伴侣蛋白和 MrkHI，以及与能量代谢（转运蛋白、细胞表面结构和转录调控）相关的蛋白。总之，本研究结果表明，YjcC 通过改变 c-di-GMP 水平来正向调节氧化应激反应和小鼠毒力，但通过改变 c-di-GMP 水平来负向调节生物膜形成和 III 型菌毛表达。氧化应激信号输入后。
