烟粉虱内共生菌16S rDNA的特性研究

Studies on Characteristics of 16S rDNA Sequences from Endosymbionts in Bemisia tabaci

摘要:

对烟粉虱内共生菌16S rDNA的酶切结果及部分生物体16S rDNA的（G+C）%分析结果表明：烟粉虱初生内共生菌的16S rDNA能够被EcoR I酶切成两个片段、而不能够分别被BamH I与Sac I酶切；烟粉虱次生内共生菌的16S rDNA没有BamH I内切酶位点、而能够分别被EcoR I或Sac I酶切成大小不同的两个片段。（G+C）mol%与菌的分类地位有关，同时还与菌的可培养能力有关。Proteobacteria γ亚纲的烟粉虱初生内共生菌与α亚纲的Rickettsia、线粒体的16S rDNA相似，富含（A+T）mol%，具低的（G+C）mol%。而γ亚纲的次生内共生菌及大肠杆菌与β亚纲的mealybugs初生内共生菌的16S rDNA相似，富含（G+C）mol%。说明初生内共生菌可能与烟粉虱同时发生,并且形成一种非常紧密的共生关系,次生内共生菌与烟粉虱关系松散一些,其特性近似于自由生活的细菌,更有可能获得纯培养体。16S rDNA的系统进化树表明，烟粉虱次生内共生菌属于Proteobacteria γ-3亚纲，而初生内共生菌属于Proteobacteria γ亚纲的另一分支。

关键词:烟粉虱,16S rDNA,内共生菌,系统发育

Abstract:

The studies on enzymes digested sites and (G+C)mol% of 16S rDNA gene from endosymbionts in B.tabaci were conducted.The results showed that:16S rDNA from primary endosymbiont in B. tabaci could be digested into two segments by EcoR I,but not by BamH I or Sac I.16S rDNA from secondary endosymbiont in B. tabaci could be digested into two segments by EcoR I or Sac I respectively, but not by BamH I. The (G+C)mol% of 16S rDNA varied according to creature species and culturable characters. For example, 16S rDNA of primary endosymbiont (Proteobacteria γ subdivision) in B. tabaci were as rich in （A+T）mol% and poor in（G+C）mol% as 16S rDNA of Rickettsia and mitochondria (Proteobacteria α subdivision), which are cell ware or unculturable microbes.The 16S rDNA from secondary endosymbiont (Proteobacteria γ subdivision) in B. tabaci and primary endosymbiont (Proteobacteria β subdivision) in mealybugs, both were unculturable, were as rich in (G+C)mol% as those of E.coli (Proteobacteria γ subdivision), a kind of culturable bacterium.As a result,primary endosymbiont was a concurrence and concerted evolution with B. tabaci. Secondary endosymbiont was similar to free-living bacteria and might be easier to be cultured. Molecular phylogenetic trees based on 16S rDNA of different creatures showed that secondary endosymbiont in B. tabaci was Proteobacteria γ-3 subdivision.Primary endosymbiont in B. tabaci was aonther Proteobacteria γ subdivision.

Key words:Bemisia tabaci, 16S rDNA,Endosymbionts, Phylogeny