固氮斯氏假单胞菌铵载体amtB基因的功能和结构分析  

MOLECULAR CLONING AND FUNCTIONAL ANALYSIS OF AMMONIUM TRANSPORTERENCODING GENES AMTB IN ASSOCIATIVE NITROGEN-FIXING BACTERIUM PSEUDOMONAS STUTZERI A1501

作　　者：侯胜强[1] 何升[1] 窦岳坦[1] 平淑珍[1] 林敏[1] 陈明[1] 

机构地区：[1]中国农业科学院生物技术研究所,北京100081

出　　处：《核农学报》2007年第6期572-576,566,共6页Journal of Nuclear Agricultural Sciences

基　　金："863"计划(2004AA214170);"973"项目(2001CB108904)

摘　　要：固氮斯氏假单胞菌(Pseudomonas stutzeri)A1501是分离自水稻根际的联合固氮细菌,属变形细菌γ亚族。全基因组序列分析表明该菌含有2个紧密连锁的的铵载体蛋白编码基因amtB1和amtB2,位于同一个操纵子中glnK基因下游。铵载体蛋白AmtB1和AmtB2分别包含12和11个跨膜结构域。为研究amtB的功能,构建了amtB极性双突变株(PKOB1)。amtB极性双突变导致菌株生长缓慢;在铵浓度分别为3.3和10mmol/L条件下,其固氮酶活仍保持在0.01mmol/L的最佳固氮条件的87%和74%,而野生型已经基本尚失固氮能力。以硝酸盐为唯一氮源时,突变株细胞培养液的铵浓度可达到3.4mmol/L,而野生型并未检测到铵,表明AmtB可能参与了P.stutzeriA1501的铵离子转运,并与固氮酶活和氮代谢相关。Pseudomonas stutzeri A1501 is a nitrogen-fixing bacterium associated with rice and classified into gamma subgroup of proteo-bacteria. Analysis of the genome revealed two linked amtB genes coding for ammonium transporter just down stream of glnK in the same operon. The AmtB1 contains 12 trans-membrane domains and the AmtB2 contains ll trans-membrane domains respectively. The amtB mutant was constructed and the mutant showed retard growth compared to the wild-type strain. The optimal ammonium concentration for high nitrogen fixation by P. stutzeri wild-type and mutant strains is O.Olmmol/L. When cultured in the medium containing 3.3 and 10mmol/L NH4^＋ , the wild type A1501 did not have any nitrogenase activity while the amtB mutant showed 86.6% and 74% of the maximal nitrogen activity cultured in the optimal ammonium concentration （0.01mmol/L）. When nitrate was used as the sole nitrogen source, the ammonium concentration of the amtB mutant in the broth reached 3.4mmol/L while that of the wild-type of strain A1501 was not detected. Thus we concluded that the AmtB is involved in the transport of ammonium and related to nitrogen fixation and metabolism.

关 键 词：斯氏假单胞菌A1501 铵载体 跨膜结构 AMTB 

分 类 号：S154.381[农业科学—土壤学]