关键词: 施氏假单胞菌A1501, 硝酸盐同化, 基因簇, 途径特异性控制

Abstract: Nitrogen-fixing Pseudomonas stutzeri A1501 can grow with nitrate/nitrite as the sole nitrogen source under aerobic conditions, suggesting that the strain has a nitrate/nitrite system in addition to nitrogen fixation and denitrification. In order to further clarify the metabolic mechanism of nitrate assimilation, bioinformatics method was used to analyze the composition and distribution of genes related to nitrate assimilation, and the pathway-specific control of nitrate assimilation was preliminarily studied. The results indicated that there were two nitrate assimilation gene clusters, nasST-nasA-nirBDnasBcobA and nasR-nasFED, distributed in different parts of the genome. In the first gene cluster, nasS-nasT encoded two-component regulatory system based on nitrate/nitrite sensing and transcription anti-termination, nasA encoded NarK/NasA family nitrate transporter, nirBD encoded nitrite reductase, nasB encoded assimilatory nitrate reductase, and cobA encodes uroporphyrin-Ⅲ C-methyltransferase involved in the synthesis of sirohaem. In the second gene cluster, nasR encoded a single-component transcription anti-terminator and nasFED encoded an ATP-dependent nitrate/nitrite transporter. Nitrate/nitrite reductase gene transcription was regulated by NasS-NasT, and nitrate/nitrite transporter gene transcription was regulated by NasR.

Key words: Pseudomonas stutzeri A1501, nitrate assimilation, gene cluster, Pathway-specific control