摘要
粪产碱菌A—15的氮素同化途径在铵培养下以GDH途径为主,而氮培养下则以GS/GOGAT途径为主,DEAE—纤维素层析,SDS—PAGE及免疫学试验均证明,粪产碱菌在铵浓度高达30mmol/L时仍有固氮酶合成,但没有固氮活性。铵和氮培养两者细菌粗提液在电泳条带上有些差异。铵培养的粪产碱菌合成的固氮酶,在解阻遏后,仍可出现固氮活性。
Associative nitrogen fixer Alcaligenes faecalis
A--15 has been isolated from rice root. It was
found that the GS and GOGAT activities in
A.faecalis were higher in N_2-grown cells than in
NH_4^+-grown cells. The opposite was true for
GDH. Thq results suggest that assimilation of
ammonia in cells fixing N_2 proceeds via the GS-
GOGAT pathway. By using DEAE-cellulose
column chromatography, SDS-PAGE, rocket
and rocket line immunoelectrophoresis etc.,
it has been shown that the nitrogenase was syn-
thesized by A. faecalis A-15 in the presence of
30 mmol/L ammonia in the culture medium even
though N_2 fixing activity is absent. The crude
extract prepared from N_2-grown cells, however,
showed another band with MW about 50 000
near the MoFe protein band on SDS-PAGE
and it disappeared in the crude extract from
NH_4^+ -grown cells. But the band reappeared
when ammonia was exhausted in the culture
medium. The results suggest that this protein
is related with the expression and regulation of
nitrogenase activity. By using antibiotic CM,
it has been shown that the activity of nitrogenase
synthesized during NH_4^+ -grown period was de-
repressed when NH_4^+ was removed from the cul-
ture medium.
关键词
粪产碱菌
固氮酶合成
铵抑制
associative nitrogen fixation
repression by ammonia
nitrogenase synthesis
