Bernhard F, Coplin D L, Geider K
Max-Planck-Institut für medizinische Forschung, Heidelberg, Germany.
Mol Gen Genet. 1993 May;239(1-2):158-68. doi: 10.1007/BF00281614.
A large ams gene cluster required for production of the acidic extracellular polysaccharide (EPS) amylovoran by the fire blight pathogen Erwinia amylovora was cloned. Tn5 mutagenesis and gene replacement were used to construct chromosomal ams mutants. Five complementation groups, essential for amylovoran synthesis and virulence in E. amylovora, were identified and designated ams A-E. The ams gene cluster is about 7 kb in size and functionally equivalent to the cps gene cluster involved in EPS synthesis by the related pathogen Erwinia stewartii. Mucoidy and virulence were restored to E. stewartii mutants in four cps complementation groups by the cloned E. amylovora ams genes. Conversely, the E. stewartii cps gene cluster was able to complement mutations in E. amylovora ams genes. Correspondence was found between the amsA-E complementation groups and the cpsB-D region, but the arrangement of the genes appears to be different. EPS production and virulence were also restored to E. amylovora amsE and E. stewartii cpsD mutants by clones containing the Rhizobium meliloti exo A gene.
克隆了由火疫病菌梨火疫欧文氏菌产生酸性细胞外多糖（EPS）淀粉果聚糖所需的一个大的ams基因簇。利用Tn5诱变和基因置换构建了染色体ams突变体。鉴定出了五个对梨火疫欧文氏菌中淀粉果聚糖合成和毒力至关重要的互补群，并将其命名为ams A - E。ams基因簇大小约为7 kb，在功能上等同于相关病原菌斯氏欧文氏菌中参与EPS合成的cps基因簇。通过克隆的梨火疫欧文氏菌ams基因，四个cps互补群中的斯氏欧文氏菌突变体恢复了黏液性和毒力。相反，斯氏欧文氏菌cps基因簇能够互补梨火疫欧文氏菌ams基因中的突变。发现amsA - E互补群与cpsB - D区域之间存在对应关系，但基因的排列似乎有所不同。含有苜蓿根瘤菌exo A基因的克隆也使梨火疫欧文氏菌amsE突变体和斯氏欧文氏菌cpsD突变体恢复了EPS产生和毒力。
