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.
出处
《核农学报》
CAS
CSCD
北大核心
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)
