光合细菌(Rhodopseudomonas capsulata)固氮活性与钼的吸收

利用紫色非硫细菌能在厌气光照下和好气黑暗下交替生长的特点和同位素~(99)Mo示踪,来探讨Rhodopseudomonas capsulata中Mo的积累与固氮酶合成的关系。 用硫酸铵和谷氨酸盐作为氮源,把Rps. capsulata置于厌气光照下生长。由于硫酸铵阻遏固氮酶,所以菌体内既无固氮酶活性也无~(99)Mo积累。而谷氨酸盐解遏固氮酶的合成,菌体则显示固氮活性并有~(99)Mo积累。 黑暗好气生长的Rps. capsulata菌体既无固氮活性,也没有~(99)Mo的积累。将这样的菌体转移到含~(99)Mo(无谷氨酸)的培养液进行光照,固氮酶活性迅速出现,同时有~(99)Mo的积累。在Rps. capsulata中钼的吸收与固氮酶的合成及活性是紧密偶联的。

MoO_4~= UPTAKE AND ACTIVITY OF NITROGEN FIXATION IN Rhodopseudomonas capsulata

Purple non-sulfur bacteria are able to readily undergo interchange between light anaerobic and dark aerobic modes of life depending on the growth conditions. The present study has made use of this flexibility in growth characteristics to examine whether Mo-accumulation is closely relate to synthesis of nitrogenase in Rhodopseudomonas capsulata.By using the radioisotope, ~(99)Mo, the results of our experiments are as follows:1. In light anaerobic grown cultures when ammonium sulfate, a repressor of nitrogenase synthesis, was used as N-source, neither nitrogenase activity nor ~(99)Mo accumulation was observed, when glutamate, a derepressor of nitrogenase synthesis, was used as N-source, both nitrogenase activity and ~(99)Mo accumulation were appeared.2. Dark aerobic grown cells of Rps. capsulata showed neither nitrogenase activity nor~(99)Mo accumulation, when such populations were transfered to the Rr-without glutamate medium containing ~(99)Mo upon illumination, the nitrogenase activity rapidly appeared and simultaneously the ~(99)Mo accumultion was detected.It is concluded that Mo uptake is closely coupled to the synthesis and activity of notrogenase in Rps. capsulata.