Assembly and functional analysis of the K. pneumoniae nif gene cluster in E. coli.
(A) Linear view of the nif gene region in the plasmid pKU7017 with the BioBrick interfaces. E, EcoRI; X, XbaI; S, SpeI; P, PstI; (B) relative nitrogenase activity of wild-type K. pneumoniae M5a1, K. pneumoniae UNF921 (pRD1), E. coli JM109 (pKU7017), and E. coli JM109 (pACYC184). Plasmid pKU7017 refers to the plasmid containing the reconstituted σ54-dependent nif system and pACYC184 was used as a negative control. Each experiment was repeated at least three times, and the error bars represent standard error.