Kleiner D, Kleinschmidt J A
J Bacteriol. 1976 Oct;128(1):117-22. doi: 10.1128/jb.128.1.117-122.1976.
When the exhaustion of sucrose or sulfate or the induction of encystment (by incubation in 0.2% beta-hydroxybutyrate) leads to termination of growth in Azotobacter vinelandii batch cultures, the nitrogenase levels in the organisms decreased rapidly, whereas glutamate synthase and glutamine synthetase levels remained unaltered. Glutamate dehydrogenase activities were low during the whole culture cycle, indicating that ammonia assimilation proceeds via glutamine. Toward depletion of sucrose or during induction of encystment, slight secretion of ammonia with subsequent reabsorption was occasionally observed, whereas massive ammonia excretion occurred when the sulfate became exhausted. The extracellular ammonia levels were paralleled by changes in the glutamine synthetase activity. The inactivation of the nitrogenase is explained as a result of rising oxygen tension, a consequence of a metabolic shift-down (reduced respiration) that occurs in organisms entering the stationary phase.
当维涅兰德固氮菌分批培养物中蔗糖或硫酸盐耗尽或诱导形成包囊（通过在0.2%β-羟基丁酸盐中培养）导致生长终止时，生物体中的固氮酶水平迅速下降，而谷氨酸合酶和谷氨酰胺合成酶水平保持不变。在整个培养周期中，谷氨酸脱氢酶活性较低，这表明氨的同化通过谷氨酰胺进行。在蔗糖耗尽时或包囊诱导期间，偶尔会观察到少量氨的分泌及随后的再吸收，而当硫酸盐耗尽时则会发生大量氨的排泄。细胞外氨水平与谷氨酰胺合成酶活性的变化平行。固氮酶的失活被解释为是由于氧张力升高所致，而氧张力升高是进入稳定期的生物体中发生的代谢下调（呼吸减弱）的结果。
