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目的:比较16S rRNA和secA1基因构建诺卡菌分属Nocardia wallacei、Nocardia farcinica、Nocardia cyriacigeorgica及Nocardia otitidiscaviarum4个种系统发育树的多样性。方法:将8株临床分离的诺卡菌菌株分别接种于脑心浸出液琼脂培养基分离培养,观察其生长情况;提取细菌DNA,采用聚合酶链式反应扩增其16S rRNA和secA1基因序列并测序,所获序列与NCBI数据库进行BLAST比对,鉴定其菌种名;选取本研究鉴定的4个属共有的40个有效发表种及本研究分离的8株诺卡菌菌株的种,通过邻接法、最大似然法分别构建16S rRNA和secA1基因序列的系统发育树并比较。结果:本研究所收集的诺卡菌分属Nocardia wallacei、Nocardia farcinica、Nocardia cyriacigeorgica及Nocardia otitidiscaviarum 4个种,且Nocardia wallacei、Nocardia farcinica及Nocardia cyriacigeorgica基于secA1基因构建的系统发育树较16S rRNA在种内菌株亲缘关系的分化差异程度高及分类多样性多(P<0.05),而Nocardia otitidiscaviarum的分化程度和分类多样性在16S rRNA和secA1基因构建的系统发育树间差异无统计学意义(P>0.05)。结论:secA1基因用于诺卡菌种群的系统发育分析和分子进化的研究,较16S rRNA具有高度分辨率的优势。
OBJECTIVE: To compare the diversity of 4 phylogenetic trees of Nocardia wallacei, Nocardia farcinica, Nocardia cyriacigeorgica and Nocardia otitidiscaviarum constructed by 16S rRNA and secA1 genes. Methods: Eight strains of Nocardia isolates were inoculated separately into agar medium of brain heart extract to observe their growth. The bacterial DNA was extracted and the 16S rRNA and secA1 gene sequences were amplified by polymerase chain reaction and sequenced , The obtained sequences were compared with the NCBI database BLAST to identify their strain name; selection of 40 genera of the 4 genera identified in this study and the strains of the 8 strains of Nocardia isolated in this study were selected by the adjoining method , The maximum likelihood method was used to construct the phylogenetic tree of 16S rRNA and secA1 gene sequences respectively and compare them. Results: Nocardia collected from this study belongs to 4 species of Nocardia wallacei, Nocardia farcinica, Nocardia cyriacigeorgica and Nocardia otitidiscaviarum. The phylogenetic trees based on the secA1 gene of Nocardia wallacei, Nocardia farcinica and Nocardia cyriacigeorgica are better than 16S rRNA in species (P <0.05). However, the differentiation degree and taxonomic diversity of Nocardia otitidiscaviarum were not significantly different between phylogenetic trees constructed by 16S rRNA and secA1 genes (P> 0.05) ). Conclusion: The secA1 gene is used for the phylogenetic analysis and molecular evolution of Nocardia populations, which has a higher resolution than 16S rRNA.