甘蔗茎内两个内生菌株16S rRNA序列分析及其生长特性

The 16S rRNA Gene Sequences and Growth Characteristics of Two Nitrogen Fixing Endobacteria Strains from Sugarcane Stalk

从两个甘蔗品种GT11和RB86-7515表面灭菌的茎中分离到两株具有固氮活性的菌株,分别编号为B11S和B8S。利用16S rRNA序列分析对其进行鉴定,并对两个菌株的生物学特性进行了比较。结果表明:B11S菌株与Stenotrophomonas maltophili菌株处在同一个分支,其序列与多个Stenotrophomonas maltophili菌株的序列相似性都达到98%以上,菌株B8S与多个土壤杆菌属细菌的序列相似性达到100%;两个菌株在温度31°C、pH为6左右时生长量最高;温度31°C、pH为6.5～7.0时固氮酶活性最高;相同浓度的蔗糖生长量大于葡萄糖,且表达固氮酶活性也最强;添加一定量的氮素有利于细菌生长和固氮酶活性的表达,但随着N含量的增加,抑制作用越来越明显。

Two N2-fixing isolates,B11S and B8S,were obtained from the surface-sterilized stalks of sugarcane variety GT11and RB86-7515 which were bred in Guangxi,China and introduced from Brazil,respectively.Both isolates showed acetylene reduction in nitrogen free media.Classification of both B11S and B8S was made on the basis of 16S rRNA sequence analysis,and the biological characteristics of the two isolates were studied.The 16S rRNA sequence of the isolate B11S had a 98.5% sequence similarity to those of many Stenotrophomonas maltophili and the 16S rRNA sequence of the isolate B8S had a 100% similarity to that of Agrobacterium tumefaciens（Rhizobium radiobacter）.For both growth and nitrogenase activity of the isolates,the optimum temperature was about 31°C.The optimum pH was about 6.0 for their growth but their nitrogenase activity.The two strains propagated more quickly and showed higher nitrogenase activity with the increase of carbon concentration in the culture media,and the effect of sucrose was better than that of the glucose.The growth and nitrogenase activity could be detected when the two strains were cultured in the media containing different concentration NH4^＋ and NO3^-,and they grew better and showed higher nitrogenase activity under suitable nitrogen contents,but the growth of the two isolates was hindered more and more strongly with the increasing of the nitrogen content.