Janczarek Monika, Rachwał Kamila
Department of Genetics and Microbiology, Institute of Microbiology and Biotechnology, Maria Curie-Sklodowska University, Akademicka 19 st., Lublin 20-033, Poland.
Int J Mol Sci. 2013 Dec 5;14(12):23711-35. doi: 10.3390/ijms141223711.
The symbiotic nitrogen-fixing bacterium Rhizobium leguminosarum bv. trifolii 24.2 secretes large amounts of acidic exopolysaccharide (EPS), which plays a crucial role in establishment of effective symbiosis with clover. The biosynthesis of this heteropolymer is conducted by a multi-enzymatic complex located in the bacterial inner membrane. PssA protein, responsible for the addition of glucose-1-phosphate to a polyprenyl phosphate carrier, is involved in the first step of EPS synthesis. In this work, we characterize R. leguminosarum bv. trifolii strain Rt270 containing a mini-Tn5 transposon insertion located in the 3'-end of the pssA gene. It has been established that a mutation in this gene causes a pleiotropic effect in rhizobial cells. This is confirmed by the phenotype of the mutant strain Rt270, which exhibits several physiological and symbiotic defects such as a deficiency in EPS synthesis, decreased motility and utilization of some nutrients, decreased sensitivity to several antibiotics, an altered extracellular protein profile, and failed host plant infection. The data of this study indicate that the protein product of the pssA gene is not only involved in EPS synthesis, but also required for proper functioning of Rhizobium leguminosarum bv. trifolii cells.
共生固氮细菌三叶草根瘤菌24.2分泌大量酸性胞外多糖（EPS），其在与三叶草建立有效的共生关系中起着关键作用。这种杂聚物的生物合成由位于细菌内膜的多酶复合物进行。负责将1-磷酸葡萄糖添加到聚异戊二烯磷酸载体上的PssA蛋白参与EPS合成的第一步。在这项工作中，我们对三叶草根瘤菌菌株Rt270进行了表征，该菌株含有一个位于pssA基因3'端的mini-Tn5转座子插入。已经确定该基因的突变在根瘤菌细胞中引起多效性效应。突变菌株Rt270的表型证实了这一点，该菌株表现出几种生理和共生缺陷，如EPS合成缺陷、运动性降低和某些营养物质的利用减少、对几种抗生素的敏感性降低、细胞外蛋白质谱改变以及宿主植物感染失败。本研究的数据表明，pssA基因的蛋白质产物不仅参与EPS合成，而且是三叶草根瘤菌细胞正常功能所必需的。
