Kosenko L V, Zatovskaia T V
Mikrobiologiia. 2004 May-Jun;73(3):350-7.
A comparative study of the lipopolysaccharides (LPS) isolated from Sinorhizobium meliloti SKHM 1-188 and two its LPS-mutants (Th29 and Ts22) with sharply decreased nodulation competitiveness was conducted. Polyacrylamide gel electrophoresis with sodium dodecyl sulfate revealed two forms of LPS in all the three strains: a higher molecular-weight LPS1, containing O-polysaccharide (O-PS), and a and lower molecular-weight LPS2 without O-PS. However, the LPS1 content in mutants was significantly smaller than in the parent strain. The LPS of the strains studied contained glucose, galactose, mannose, xylose, three nonidentified sugars--X1 (TGlc 0.53), X2 (TGlc 0.47), and X3 (TGlc 0.43), glucosamine, and ethanolamine, while the LPS of S. meliloti SKHM1-188 additionally contained galactosamine, glucuronic and galacturonic acids, and 2-keto-3-deoxyoctulosonic acid (KDO), as well as fatty acids, such as 3-OH C14:0, 3-OH C15:0, 3-OH C16:0, 3-OH C18:0, nonidentified hydroxy X (T3-OH C14:0 1.33), C18:0, and unsaturated C18:1 fatty acids. The LPS of both mutants were similar in the component composition but differed from the LPS of the parent strain by a lower X2, X3, and 3-OH C 14:0 content and a higher KDO, C18:0, and hydroxy X content. The LPS of all the strains were subjected to mild hydrolysis with 1% acetic acid and fractionated on a column with Sephadex G-25. The higher molecular weight fractions (2500-4000 Da) contained a set of sugars typical of intact LPS and, supposedly, corresponded to the LPS polysaccharide portion (PS1). In the lower molecular weight fractions (600-770 Da, PS2), glucose and uronic acids were the major components; galactose, mannose, and X1 were present in smaller amounts. The PS1/PS2 ratio for the two mutants was significantly lower than for strain SKHM1-188. The data obtained show that the amount of O-PS-containing molecules (LPS1) in the heterogeneous lipopolysaccharide complex of the mutants was smaller than in the SKHM1-188 LPS; this increases the hydrophobicity of the cell surface of the mutant bacteria. This supposedly contributes to their nonspecific adhesion on the roots of the host plant, thus decreasing their nodulation competitiveness.
对从苜蓿中华根瘤菌SKHM 1-188及其两个结瘤竞争力急剧下降的脂多糖（LPS）突变体（Th29和Ts22）中分离出的脂多糖进行了比较研究。十二烷基硫酸钠聚丙烯酰胺凝胶电泳显示，所有三个菌株中都有两种形式的LPS：一种分子量较高的LPS1，含有O-多糖（O-PS），另一种分子量较低的LPS2，不含O-PS。然而，突变体中LPS1的含量明显低于亲本菌株。所研究菌株的LPS含有葡萄糖、半乳糖、甘露糖、木糖、三种未鉴定的糖——X1（TGlc 0.53）、X2（TGlc 0.47）和X3（TGlc 0.43）、葡糖胺和乙醇胺，而苜蓿中华根瘤菌SKHM1-188的LPS还含有半乳糖胺、葡萄糖醛酸和半乳糖醛酸，以及2-酮-3-脱氧辛糖酸（KDO），还有脂肪酸，如3-OH C14:0、3-OH C15:0、3-OH C16:0、3-OH C18:0、未鉴定的羟基X（T3-OH C14:0 1.33）、C18:0和不饱和C18:1脂肪酸。两个突变体的LPS在组成成分上相似，但与亲本菌株的LPS不同，X2、X3和3-OH C 14:0的含量较低，而KDO、C18:0和羟基X的含量较高。所有菌株的LPS都用1%的乙酸进行轻度水解，并在Sephadex G-25柱上进行分级分离。较高分子量的级分（2500-4000 Da）含有一组完整LPS特有的糖，据推测，对应于LPS多糖部分（PS1）。在较低分子量的级分（600-770 Da，PS2）中，葡萄糖和糖醛酸是主要成分；半乳糖、甘露糖和X1的含量较少。两个突变体的PS1/PS2比值明显低于SKHM1-188菌株。获得的数据表明，突变体的异质脂多糖复合物中含O-PS的分子（LPS1）的量比SKHM1-188 LPS中的少；这增加了突变细菌细胞表面的疏水性。据推测，这有助于它们在宿主植物根部的非特异性粘附，从而降低它们的结瘤竞争力。
