Liaw Shwu-Jen, Lai Hsin-Chih, Ho Shen-Wu, Luh Kwen-Tay, Wang Won-Bo
School and Graduate Institute of Medical Technology1 and Graduate Institute of Microbiology3, College of Medicine, National Taiwan University, 1 Jen Ai Road, 1st Section, Taipei, Taiwan, Republic of China 2Department of Laboratory Medicine, National Taiwan University Hospital, Taipei, Taiwan, Republic of China.
J Med Microbiol. 2003 Jan;52(Pt 1):19-28. doi: 10.1099/jmm.0.05024-0.
Swarming by Proteus mirabilis involves differentiation of typical short vegetative rods into filamentous hyper-flagellated swarm cells that undergo cycles of rapid and co-ordinated population migration across surfaces and exhibit high levels of virulence gene expression. RsmA (repressor of secondary metabolites) and CsrA, its homologue in Escherichia coli, control many phenotypic traits, such as motility and pathogenesis in Erwinia species, glycogen biosynthesis, cell size and biofilm formation in Escherichia coli and swarming motility in Serratia marcescens. To investigate the role of RsmA in Proteus mirabilis, the rsmA gene from Proteus mirabilis (hereafter referred to as rsmA(Pm)) was cloned. RsmA(Pm) showed high sequence similarity to Escherichia coli CsrA and RsmA cloned from Erwinia carotovora subsp. carotovora, Serratia marcescens, Haemophilus influenzae and Bacillus subtilis and could complement an Escherichia coli csrA mutant in glycogen synthesis. A low-copy-number plasmid carrying rsmA(Pm) expressed from its native promoter caused suppression of swarming motility and expression of virulence factors in Proteus mirabilis. mRNA stability assays suggested that RsmA(Pm) inhibited virulence factor expression through promoting mRNA degradation. RsmA homologues cloned from Serratia marcescens and Erwinia carotovora subsp. carotovora could also inhibit swarming and virulence factor expression in Proteus mirabilis.
奇异变形杆菌的群体游动涉及典型的短营养杆状细胞分化为丝状、超鞭毛化的群体细胞，这些细胞经历跨表面的快速且协调的群体迁移循环，并表现出高水平的毒力基因表达。RsmA（次生代谢产物阻遏物）及其在大肠杆菌中的同源物CsrA控制许多表型特征，如欧文氏菌属中的运动性和致病性、大肠杆菌中的糖原生物合成、细胞大小和生物膜形成以及粘质沙雷氏菌中的群体游动性。为了研究RsmA在奇异变形杆菌中的作用，克隆了奇异变形杆菌的rsmA基因（以下简称rsmA(Pm)）。rsmA(Pm)与大肠杆菌CsrA以及从胡萝卜软腐欧文氏菌胡萝卜亚种、粘质沙雷氏菌、流感嗜血杆菌和枯草芽孢杆菌中克隆的RsmA具有高度序列相似性，并且可以在糖原合成方面互补大肠杆菌的csrA突变体。携带从其天然启动子表达的rsmA(Pm)的低拷贝数质粒导致奇异变形杆菌的群体游动性和毒力因子表达受到抑制。mRNA稳定性分析表明，RsmA(Pm)通过促进mRNA降解来抑制毒力因子表达。从粘质沙雷氏菌和胡萝卜软腐欧文氏菌胡萝卜亚种中克隆的RsmA同源物也可以抑制奇异变形杆菌的群体游动和毒力因子表达。
