花生根瘤菌在自生条件下固氮和吸氢相关性

Inter-connection between Activities of Nitrogenase and Hydrogenase in Free-living Strain of Rhizobium arachis

花生根瘤菌x_(-1)菌株在自生条件下和合适的培养基中,可诱导固氮酶及氢酶的活性,固氮酶反应产生的H_2(内源H_2)能直接诱导氢酶,氢酶活性表达的时间进程是在固氮反应之后,在外源H_2的存在下,固氮酶和氢酶则可同时表达,不同有机碳化合物对固氮酶与氢酶的影响不同,丙酮酸明显提高固氮活性,但对氨酶没有促进作用,蔗糖对固氮活性没有促进作用但对吸氢表现促进作用,分子H_2明显提高固氮活性,2.4-二硝基苯酚抑制需H_2的固氮活性,在外源H_2存在下其抑制作用更明显,铵抑制固氮酶的形成、固氮酶受铵抑制时氢酶也相应受到抑制。

Under normal condition, culture medium for expression of nitrogenase is differentiated from that of hydrogenase, by improvement of the medium, we proved that both niteogenase and hydrogenase activities of R. arachis strain X8-1 can be expressed in free-living cultures. H2, produced by nitrogenase, induced the hydrogenase, consequantly the time course plot of the hydrogenase activity lagged behind the nitrogenase activity. However, time course plots of the activities of nitroge-nase and hydrogenase activities were synchronous if the exogenous H2 was added in the begining of culture. Compared the effect of some carbon compounds on nitrogenase and hydrogenase activities, the results showed that pyruvate and succinate significantly supported the nitrogenase activity but their effect on hydrogenase activity was slight. On the contrary, sucrose and maltose were more efficient, for increasing hydrogenase activity than for nitrogenase activity. H2 significantly enhanced nitrogenase activity. 2, 4-Dinitrophenol, an uncoupler of oxidative phosphorylation, inhibited the H2-dependent C2H2 reduction. This inhibition was more efficient in the presence of exogenous H2. Ammonium inhibited nitrogenase activity. In this situation hydrogenase activity also was inhibited unless the exogenous H2 was added.