固氮粪产碱菌ntrC基因的表达及固氮调节功能研究  

Expression of ntrC Gene and Its Regulatory Function of Nitrogen Fixation in Alcaligenes faecalis

作　　者：程红梅[1] 林敏[1] 贾士荣[2] 

机构地区：[1]中国农业科学院原子能利用研究所,北京100094 [2]中国农业科学院生物技术研究中心,北京100081

出　　处：《农业生物技术学报》1996年第1期81-86,共6页Journal of Agricultural Biotechnology

摘　　要：采用双亲结合方法,将粪产碱菌(Alcaligenes faecalis)A1501ntrC 和 ntrC-lacZ 融合基因转入 A1501中,获得携带双拷贝 ntrC 的结合子 A1501(pLAC1)和 ntrC-lacZ 融合基因的结合子A1501(pLAC2)。在微好氧条件下,当铵为6 mmol 时结合子 A1501(pLAC1)仍保持34.8%的固氮活性,表明在粪产碱菌中 ntrC 具有固氮正调节功能。在不同铵、氧、pH 和盐浓度等条件下测定结合子 A1501(pLAC2)的β-Galactosidase 活性,结果表明在微好氧条件下,ntrC 表达不受铵浓度调节,呈组成型表达,最高活性为891β。在好氧条件下,ntrC 表达活性随铵浓度提高而递减,无铵条件下β-Galactosidase 活性为2161.53μ,当 NH_4^-浓度为30 mmol 时,为149μ。pH 为6～10及 NaCl浓度在0～2.4 mol 之间,粪产碱菌 ntrC-lacZ 融合基因仍能保持高水平的表达活性。The plasmid pLAC1 or pLAC2 contained ntrC gene or ntrC-lacZ fusion respectively was in- troduced into Alcaligenes faecalis wild type strain A1501 by conjugation.At microaerobic condition,34. 8% of nitrogen fixing activity of A1501(pLAC1),that contained two copies of ntrC gene,was recovered when the concentration of NH_4^+ was 6 mmol·L^(-1).This suggested that the ntrC gene in Alcaligenes fae- calis had positive regulatory function for nitrogen fixation.The β-Galactosidase activity of A1501(pLAC2) was analyzed at different concentrations ofNH_4^+,O_2,Na^+ and pH values.Results showed that:a)At mi- croaerobic condition,the expression of ntrC-lacZ fusion was constitutive and was not inhibited by ammoni- a,The highest activity of β-Galactosidase was 891μ;b)At aerobic condition,the β-Galactosidase activity of A1501(pLAC2)decreased gradually with the increase of ammonia concentration.β-Galactosidase activi- ty of A1501(pLAC2)was 2161.53 μ in NH_4^+-free medium while the value for medium contained 30 mmol ·L^(-1)NH_4^+ was only 149 μ.When pH ranged 6～10 and the concentration of Na^+ was 0～2.4 mol,the expression of ntrC-lacZ fusion in Alcaligenes faecalis maintained higher activities.

关 键 词：粪产碱菌 融合基因 固氮 表达调节 

分 类 号：Q753[生物学—分子生物学] S154.381[农业科学—土壤学]