Transcription and activities of NOx reductases in Agrobacterium tumefaciens:: the influence of nitrate, nitrite and oxygen availability
Transcription and activities of NOx reductases in Agrobacterium tumefaciens:: the influence of nitrate, nitrite and oxygen availability
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DOI：
10.1111/j.1462-2920.2007.01557.x
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发表时间：
2008-11-01
影响因子：
5.1
通讯作者：
Bakken, Lars
中科院分区：
文献类型：
--
作者：
Bergaust, Linda;Shapleigh, James;Bakken, Lars
通过监测不同初始氧、硝酸盐或亚硝酸盐浓度的搅拌分批培养物中的氧消耗、nirK和norB的转录以及亚硝酸盐、一氧化氮（NO）和一氧化二氮的浓度，研究了根癌农杆菌进行从有氧呼吸到无氧呼吸的平衡过渡的能力。硝酸盐浓度（0.2-2 mM）不影响氧消耗，也不影响反硝化作用开始时的氧浓度（1-2 μ M）。另一方面，亚硝酸盐（0.2-2 mM）在达到约20 μ M时会减缓氧气消耗，并在氧气浓度达到10-17 μ M时引起主动反硝化的启动。不平衡的转换发生在治疗与高细胞密度（即从好氧到缺氧条件的快速过渡），被视为NO积累到μ M浓度，并阻碍一氧化二氮的生产。这种现象在亚硝酸盐处理中最为严重，并降低了细胞在随后的有氧条件下呼吸氧气的能力。norB的转录本仅在反硝化作用活跃期间检测到。相反，在此期间之前和之后，检测到低水平的nirK转录本。结果表明，从有氧代谢到厌氧代谢的转变是一个监管的挑战，与生存和微量气体从微生物细菌的排放的影响。
The ability of Agrobacetrium tumefaciens to perform balanced transitions from aerobic to anaerobic respiration was studied by monitoring oxygen depletion, transcription of nirK and norB, and the concentrations of nitrite, nitric oxide (NO) and nitrous oxide in stirred batch cultures with different initial oxygen, nitrate or nitrite concentrations. Nitrate concentrations (0.2-2 mM) did not affect oxygen depletion, nor the oxygen concentration at which denitrification was initiated (1-2 mu M). Nitrite (0.2-2 mM), on the other hand, retarded the oxygen depletion as it reached approximate to 20 mu M, and caused initiation of active denitrification as oxygen concentrations reached 10-17 mu M. Unbalanced transitions occurred in treatments with high cell densities (i.e. with rapid transition from oxic to anoxic conditions), seen as NO accumulation to mu M concentrations and impeded nitrous oxide production. This phenomenon was most severe in nitrite treatments, and reduced the cells' ability to respire oxygen during subsequent oxic conditions. Transcripts of norB were only detectable during the period with active denitrification. In contrast, nirK transcripts were detected at low levels both before and after this period. The results demonstrate that the transition from aerobic to anaerobic metabolism is a regulatory challenge, with implications for survival and emission of trace gases from denitrifying bacteria.