Control of gene expression in blue-green algae
Control of gene expression in blue-green algae
复制标题
蓝绿藻基因表达的控制
作者：
R. A. Singer;W. Doolittle
蓝绿藻是原核生物的一个主要类群，在许多方面与光合真核生物的叶绿体相似，也许在遗传学上与之相关。在这个组中的代谢控制机制是感兴趣的，因为它的独特的进化位置，因为它的许多成员是专性光合自养生物，因此可能会显示模式的控制不同于那些已知的异养细菌。事实上，卡尔和他的合作者1 -3提出，蓝绿色一般不像异养生物通常那样在基因表达水平上调节代谢。外源代谢物可以被同化，但它在细胞中的存在并不诱导（或抑制）负责其自身代谢（或生物合成）的酶的合成。因此，这些工作者认为，外源性底物通常不支持显着的黑暗生长，甚至不刺激光照下的生长，因为蓝绿色根本无法调节中间代谢酶的水平，以适应除CO2以外的任何碳源或除光照以外的任何能源。
THE blue-green algae are a major group of prokaryotes in many ways resembling, and perhaps phylogenetically related to, the chloroplasts of photosynthetic eukaryotes. Metabolic control mechanisms in this group are of interest because of its unique evolutionary position and because many of its members are obligate photoautotrophs and as such may show patterns of control different from those known in heterotrophic bacteria. Indeed, Carr and his collaborators1–3 have proposed that blue-greens do not in general regulate metabolism at the level of gene expression, as heterotrophs commonly do. An exogenous metabolite may be assimilated, but its presence in the cell does not induce (or repress) the synthesis of enzymes responsible for its own catabolism (or biosynthesis). Thus, these workers argue, exogenous substrates do not usually support significant dark growth, or even stimulate growth in the light, because blue-greens simply cannot adjust the levels of the enzymes of intermediary metabolism to accommodate any source of carbon other than CO2 or any source of energy other than light1.