奇古菌亚硝酸盐还原酶基因相似基因的多样性

Diversity of thaumarchaeal nitrite reductase (nirK)-like genes in environments

摘要:

摘要:【目的】氨氧化古菌(Ammonia-oxidizing archaea，AOA)是奇古菌门中的唯一类群，广泛分布于各个生态系统中，对氮素生物地球化学循环起着重要作用。亚硝酸还原酶是反硝化作用的关键酶，目前关于AOA反硝化作用的研究较少，对AOA 亚硝酸盐还原酶基因多样性的研究有利于揭示AOA在反硝化中的作用。【方法】本研究以水体、沉积物和土壤为研究对象，构建了奇古菌样的nirK基因克隆文库，研究了这些环境中nirK相似基因的多样性。【结果】对奇古菌样的nirK基因文库及其序列分析表明:湖水及其沉积物的 nirK基因克隆文库得到10个OTUs，菜田土壤和水样则有8个OTUs;系统发育进化树表明这些nirK氨基酸序列和Candidatus Nitrosopumilus koreensis AR1，Nitrosopumilus maritimus SCM1最为相似，但相似度较低(53%－68%)。克隆文库多样性指数分析表明:所有样品都存在不同类型的nirK基因，水体样品nirK基因类型的多样性和均匀度高于土壤样品，菜田土壤的nirK基因类型多样性最高，分布最均匀。【结论】本研究表明土壤和淡水环境中奇古菌门nirK基因也具有较高的多样性，并且这些基因型与海洋样品差异非常大，这些基因编码的亚硝酸盐还原酶可能对这些环境中的反硝化作用有重要意义。

Abstract:

Abstract:［Objective］Nitrite reductase encoded by nirK is a key enzyme to denitrification，and is found in ammoniaoxidizing archaea (AOA)．Based on the diversity of nirK，it was good to study the functions of nitrite reductase to AOA on denitrification.［Methods］ We constructed nirK gene clone libraries based on the nirK gene PCR products of water，sediment and soil，screened the positive clones by restriction fragment length polymorphism (RFLP)，and sequenced the representative fragments from positive clones．［Results］RFLP analysis of the clone libraries shows that there were 10 OTUs in fresh water and sediment，8 in vegetable soil and its nearby water．Phylogenetic analysis indicated that the amino acid sequences of these nirK were most closely related to the Candidatus Nitrosopumilus koreensis AＲ1 and Nitrosopumilus maritimus SCM1 with similarities ranging from 53% to 68%．Diversity index of clone libraries shows there were many different types of nirK genes in all samples．Diversity and evenness index of nirK gene of water samples was higher than soil samples whreas vegetable field samples were the richest.［Conclusion］Thaumarchaeote nirK gene had high diversity in soil and freshwater environments which were very different from ocean sample． The nirK gene encoding nitrite reductase might be important for thaumarchaeote denitrification．