Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Edificio Severo Ochoa, 1a planta, Campus de Rabanales, Córdoba, 14071, Spain.
Biochem Soc Trans. 2011 Dec;39(6):1838-43. doi: 10.1042/BST20110688.
In the context of the global nitrogen cycle, the importance of inorganic nitrate for the nutrition and growth of marine and freshwater autotrophic phytoplankton has long been recognized. In contrast, the utilization of nitrate by heterotrophic bacteria has historically received less attention because the primary role of these organisms has classically been considered to be the decomposition and mineralization of dissolved and particulate organic nitrogen. In the pre-genome sequence era, it was known that some, but not all, heterotrophic bacteria were capable of growth on nitrate as a sole nitrogen source. However, examination of currently available prokaryotic genome sequences suggests that assimilatory nitrate reductase (Nas) systems are widespread phylogenetically in bacterial and archaeal heterotrophs. Until now, regulation of nitrate assimilation has been mainly studied in cyanobacteria. In contrast, in heterotrophic bacterial strains, the study of nitrate assimilation regulation has been limited to Rhodobacter capsulatus, Klebsiella oxytoca, Azotobacter vinelandii and Bacillus subtilis. In Gram-negative bacteria, the nas genes are subjected to dual control: ammonia repression by the general nitrogen regulatory (Ntr) system and specific nitrate or nitrite induction. The Ntr system is widely distributed in bacteria, whereas the nitrate/nitrite-specific control is variable depending on the organism.
在全球氮循环的背景下，无机硝酸盐对海洋和淡水自养浮游植物的营养和生长的重要性早已得到认可。相比之下，异养细菌对硝酸盐的利用在历史上受到的关注较少，因为这些生物体的主要作用传统上被认为是溶解和颗粒有机氮的分解和矿化。在基因组序列出现之前，人们就知道一些，但不是所有的异养细菌都能够以硝酸盐作为唯一氮源进行生长。然而，对目前可用的原核基因组序列的研究表明，同化硝酸盐还原酶（Nas）系统在细菌和古菌异养生物中具有广泛的系统发育分布。到目前为止，硝酸盐同化的调控主要在蓝细菌中进行研究。相比之下，在异养细菌菌株中，硝酸盐同化调控的研究仅限于荚膜红细菌、产酸克雷伯氏菌、维氏固氮菌和枯草芽孢杆菌。在革兰氏阴性菌中，nas 基因受到双重控制：一般氮调节（Ntr）系统对氨的抑制和特定硝酸盐或亚硝酸盐的诱导。Ntr 系统在细菌中广泛分布，而硝酸盐/亚硝酸盐的特异性控制则因生物体而异。
