Effects of additives on efficiency and specificity of ligase detection reaction.

Ligase detection reaction (LDR) is adaptable to a wide variety of applications ranging from scientific research to clinical diagnosis, especially in the field of nucleotide polymorphism discrimination and analysis. Efficiency and specificity of LDR are the most two important characteristics that influence its application. To improve the specificity or efficiency of ligase, optimization of the design of LDR probes and the reaction of LDR were investigated previously by most researchers. But the effects of additives on LDR have not been reported. In this study, the effects of additives (DMSO, Tween-20, glycerol, formamide, and PEG- 6000) on LDR efficiency and specificity were investigated. The results showed that all of these compounds, except for Tween-20, could improve the specificity of LDR. PEG-6000 was proved to be the best additive among the five tested with an optimal concentration of 5% at which the highest yield was obtained with a relatively improved specificity.

Comparative quantification of human intestinal bacteria based on cPCR and LDR/LCR.

AIM: To establish a multiple detection method based on comparative polymerase chain reaction (cPCR) and ligase detection reaction (LDR)/ligase chain reaction (LCR) to quantify the intestinal bacterial components. METHODS: Comparative quantification of 16S rDNAs from different intestinal bacterial components was used to quantify multiple intestinal bacteria. The 16S rDNAs of different bacteria were amplified simultaneously by cPCR. The LDR/LCR was examined to actualize the genotyping and quantification. Two beneficial (Bifidobacterium, Lactobacillus) and three conditionally pathogenic bacteria (Enterococcus, Enterobacterium and Eubacterium) were used in this detection. With cloned standard bacterial 16S rDNAs, standard curves were prepared to validate the quantitative relations between the ratio of original concentrations of two templates and the ratio of the fluorescence signals of their final ligation products. The internal controls were added to monitor the whole detection flow. The quantity ratio between two bacteria was tested. RESULTS: cPCR and LDR revealed obvious linear correlations with standard DNAs, but cPCR and LCR did not. In the sample test, the distributions of the quantity ratio between each two bacterial species were obtained. There were significant differences among these distributions in the total samples. But these distributions of quantity ratio of each two bacteria remained stable among groups divided by age or sex. CONCLUSION: The detection method in this study can be used to conduct multiple intestinal bacteria genotyping and quantification, and to monitor the human intestinal health status as well.