STUDY ON THE ANALYSIS OF TAXONOMIC DISTANCE AMONG

利用16 SrRNA序列对原核生物进行了系统分类，并通过比较16 SrRNA序列的差异，定量测定了各独立种间的遗传距离。然而，一些已建立的物种的16 SrRNA序列却很明显是相同的，在这种情况下，我们需要使用其他方法来区分密切相关的物种。定量DNA/DNA杂交方法是一种官方认可的确定细菌种属的方法。但该方法操作困难，且所用DNA常与多糖结合，影响DNA/DNA杂交体的定量分析。建立了DNA纯度的评价参数和DNA中鸟嘌呤和胞嘧啶含量的快速测定方法，以指导DNA/DNA杂交实验。通过测量235/260 nm的吸光度和糖的蒽酮定量方法成功地预测了RNA和多糖污染。用SYBR绿色1荧光灯，用光循环仪即时测定DNA中鸟嘌呤和胞嘧啶的含量。这些信息对于确定最佳温度下的定量DNA/DNA杂交非常有用。许多科学家成功地进行了区分物种内菌株的试验。我们使用Ceul限制性内切酶来评估菌株之间的距离。该方法具有优势，因为Ceul消化产生的条带指示核糖体RNA操纵子的拷贝数。通过对片段大小的分析，为分析基因重组历史提供了有用的信息。

Prokaryotes were phylogenetically classified by 16SrRNA sequences and genetic distance among independent species were quantitatively measured simply by comparing their 16SrRNA differences. However, it become clear that some established species shares same 16SrRNA sequences.In this case, we need to use other method to differentiate closely related species. Quantitative DNA/DNA hybridization method is a officially accepted method to define a bacterial species. However, this method is difficult to perform and DNA used for this method is often cotaminated with polysaccharide, which interfers quantitative analysis of DNA/DNA hybrid. We established several parameters to evaluate DNA purity and a rapid measuring method of guanine plus cytosine contents of DNA to define DNA/DNA hybridization experiments. RNA and polysaccharide contamination was successfully predicted by measuring absorbance of 235/260 nm and Anthrone quantitation method of sugars. Guanine plus cytosine content of DNA was instantly measured by Light cycler with SYBR Green 1 fluorescence. This information is very useful to define quantitative DNA/DNA hybridization at optimal temperature. Trials to differentiate strains within a species were successfully introduced by many scientists. We used Ceul restriction enzyme to evaluate distances among strains. This method has a advantage because bands generated by the Ceul digestion indicate numbers of copies of ribosomal RNA operon. From fragment analysis of generated size offered useful information to analyze gene recombination history.