Abstract:

The genes associated with nitrogen fixation are often grouped in one or several contiguous units of the diazotrophic genome, which are the genetic basis of biological nitrogen fixation. Among them there are nitrogenase structural genes nifHDK, and many additional genes involved in electron transport and FeMocofactor biosynthesis and assembly. This paper conducted simple comparative analysis on the relationship between organization and evolution of nitrogenfixation gene clusters. Through comparing the nitrogenfixation gene clusters in all sequenced diazotrophs, we found that there were at least 6 conservative genes: nifH, nifD, nifK, nifE, nifN, and nifB, and all of them were essential for nitrogen fixation in characterized systems. Although there are some differences in their structures and organizing patterns by different diazotrophs. These nitrogenfixation gene clusters are structurally, mechanistically, and phylogenetically closely related. Meanwhile, the paper also prospected directions for studying nitrogenfixation genes. It aimed to provide theoretical basis for further studying the mechanism of biological nitrogen fixation and understanding the evolution of microbial nitrogen fixation.

Key words: biological nitrogen fixation, nitrogenfixation gene clusters, structure and evolution

摘要：

在固氮菌基因组中,固氮相关基因都是作为一个或几个基因簇存在,是细菌生物固氮的遗传基础。这其中包括固氮酶结构基因nifHDK,以及参与电子转运和铁钼辅因子合成及组装的其他相关基因。对不同菌中固氮基因簇的结构和进化进行了简要的比较分析。比较所有已测序固氮菌中的固氮基因簇,发现均至少含有六个保守基因:nifH、nifD、nifK、nifE、nifN和nifB,并且这6个基因在所有已鉴定的系统中都是固氮所必需的。尽管在不同种类的固氮微生物中,固氮基因簇的构成及组织模式有所不同,但是它们在结构、催化机制和系统进化上紧密相关。同时也对固氮基因的研究方向提出了展望。旨在为今后进一步研究生物固氮机制,了解固氮微生物的进化,扩展生物固氮多样性提供理论基础。

关键词: 生物固氮；固氮基因簇；结构与进化