中文摘要：

为研究外源寡核苷酸对2种典型肠道菌—双歧杆菌（Bifidobacterium adolescentis）和大肠杆菌（Escherichia coli）的影响,向核酸营养缺乏型的培养基中分别添加39和61nt的2种寡核苷酸,利用平板菌落计数和16SrDNA定量法比较了外源核酸对双歧杆菌和大肠杆菌单独生长及2种细菌混合生长的影响。研究显示,虽然添加2种外源寡核苷酸对单独培养的2种细菌的生长都有不同程度的促进效果,但对于混合培养的2种细菌,大肠杆菌的生长会因双歧杆菌的生长而受到一定的抑制,当大肠杆菌和双歧杆菌比例增加到1∶10时,大肠杆菌生长的抑制率可达到27.7%。结果表明,肠道微生物可以通过降解本研究中的2种寡核苷酸,达到主动利用外源的核酸类物质、促进自身生长的目的,体外实验结果预示,一些特殊序列的寡核苷酸可能对改善肠道菌群的平衡具有潜在的积极作用。

英文摘要：

The safety and function of dietary nucleic acids on human body have received significant attentions in recent years.Adding exogenous nucleotides was widely recommended in infant formula milk powder and infant food for their beneficial functions.In the past,the researches mainly focused on the effect of mononucleotides on intestinal microorganisms.The nucleic acids are taken in mostly through food,and oligonucleotides are the important form of intake nucleic acids.However,there was less study on the influence of oligonucleotides on the intestinal microorganisms.In this study,we employed two kinds of oligonucleotides to investigate their effects on the growth of two typical intestinal bacteria Escherichia coli and Bifidobacteriumadolescentis.Firstly,E.coli and B.adolescentis were cultured separately in the medium lacking nucleic acids,and then two kinds of oligonucleotides（39nt and 61 nt in length）were added into the medium.The primary results showed that the two oligonucleotides promoted the growth of E.coli and B.adolescentis,respectively.Considering the complex intestinal bacterial community,E.coli and B.adolescentis were then culture together,and real time quantitative PCR was used to quantifying the 16 SrRNA gene（rDNA）of the two bacteria.Compared with the control,the added oligonucleotides promoted the B.adolescentis growth.However,it inhibited the growth of E.coli obviously.To study the form of the oligonucleotides appropriate for bacteria,the collected bacteria were broken with ultrasonic wave with the released cytoplasm mixed with the oligonucleotides in order to simulate the existence of oligonucleotides in bacteria.The results of electrophoresis showed that the oligonucleotides remained undestroyed in the medium;however,they were degradable in bacterial cytoplasm.The results also showed that the degradation rate of 39 nt oligonucleotide was faster than that of the 61 nt oligonucleotide in both bacteria.The results indicated that the intestinal microorganisms preferred to degrade oligonucleotides i