日勾维肠杆菌中固氮基因表达的调节

用^(32)P中标记的nifHDK和nifA基因探针与日勾维肠杆菌(E.gergoviae 57-7)DNA杂交,证明在E.gergoviae 57-7中存在类似nifHDK及nifA的基因.经接合转移法把nifHpromotor:IacZ融合子引入E.gergoviae 57-7,在转交子中可测到较高的β-半乳糖苷酶活性,表明在E.gergoviae 57-7中类似nifA基因对固氮基因表达的调节特性与K.pneumoniae的类似.载有组成型表达nifA基因的质粒pCK3经接合转移法引入E.gergoviae 57-7,转交子生长速率与野生型相似,在高氨下合成固氮酶并能恢复50%以上的固氮活性.

REGULATION OF NIF GENE EXPRESSION IN AN ASSOCIATIVE DIAZOTROPH-ENTEROBACTER GERGOVIAE 57-7

The nifA-like gene and nifHDK gene of E. gergoviae 57-7 were identified by southern DNA-DNA hybridization with a 32P-labeled nifA and a nifHDK probe. The nifA-like gene in E. gergoviae 57-7 activated the nifH:lacZ fusion which was introduced into E. gergoviae 57-7 by plasmid pSF2. The properties of nifA-like gene in E. gergoviae 57-7 was very similar with nifA in K. pneumoniae. A K. pneumoniae nifA gene expressed constitutively was introduced into E. gergoviae 57-7 by plasmid pCK3. A NH4 tolerant transconjugate was obtained and its characterization was studied.