Stacey G, Bottomley P J, Van Baalen C, Tabita F R
J Bacteriol. 1979 Jan;137(1):321-6. doi: 10.1128/jb.137.1.321-326.1979.
The development of the heterocyst by filamentous nitrogen-fixing cyanobacteria provides an attractive model system for studying cellular differentiation. Heterocyst synthesis is repressed by the presence of exogenous combined nitrogen. In this report, it is shown that the tryptophan analog, D,L-7-azatryptophan (Aza-T), is capable of relieving the repressive effect of exogenous NH4NO3 on heterocyst and nitrogenase synthesis. In nitrogen-fixing cultures, the presence of 20 micron Aza-T increases the heterocyst frequency twofold. The glutamate analog, L-methionine-D,L-sulfoximine (MSX), has also been shown to cause a derepression in the synthesis of heterocysts and nitrogenase. However, unlike MSX, Aza-T does not appear to exert its effects by inhibiting the activity of glutamine synthetase. Therefore, glutamine synthetase may not be the sole key to the derepression of heterocyst and nitrogenase development in the cyanobacteria. It is hoped that a study of Aza-T action may lead to the elucidation of a novel control mechanism.
丝状固氮蓝细菌异形胞的发育为研究细胞分化提供了一个有吸引力的模型系统。外源化合态氮的存在会抑制异形胞的合成。在本报告中，研究表明色氨酸类似物D，L-7-氮杂色氨酸（Aza-T）能够解除外源NH4NO3对异形胞和固氮酶合成的抑制作用。在固氮培养物中，20微米的Aza-T可使异形胞频率增加两倍。谷氨酸类似物L-甲硫氨酸-D，L-亚砜亚胺（MSX）也已被证明会导致异形胞和固氮酶合成的去抑制。然而，与MSX不同，Aza-T似乎不是通过抑制谷氨酰胺合成酶的活性来发挥作用。因此，谷氨酰胺合成酶可能不是蓝细菌中异形胞和固氮酶发育去抑制的唯一关键因素。希望对Aza-T作用的研究可能会导致阐明一种新的控制机制。
