Impact of inorganic carbon availability on microcystin production by microcystis aeruginosa PCC 7806
Impact of inorganic carbon availability on microcystin production by microcystis aeruginosa PCC 7806
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DOI：
10.1128/aem.01253-07
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发表时间：
2007-11-01
影响因子：
4.4
通讯作者：
Benndorf, Juergen
中科院分区：
文献类型：
--
作者：
Jaehnichen, Sabine;Ihle, Tilo;Benndorf, Juergen
对铜绿微囊藻PCC7806进行了分批培养实验，以验证微囊藻毒素(MCYSTs)是在细胞内无机碳(C-I、C-I)相对缺乏的情况下产生的。在第一个实验中，研究了在C-I，C-I缺乏增加的条件下，通过用其钾类似物取代介质中的碳酸氢钠来限制钠依赖的碳酸氢盐的吸收，从而获得MCYST的生产。在第二个实验中使用了相同的实验方法来比较野生型铜绿假单胞菌PCC7806和其mcyB突变体的反应，mcyB突变体缺乏产生MCYSTs的能力。在第三个实验中，研究了改变C-I、C-I状态对MCYST生产的影响，但没有抑制依赖于钠的碳酸氢盐转运蛋白；相反，我们对暗-光周期进行了详细的研究。在所有的实验中，相对的C-I，C-I缺乏是由一个升高的可变荧光信号指示的，并导致藻蓝蛋白细胞配额增加。随着C-I、C-I缺乏率的增加，MCYST细胞配额(第一次和第三次实验)和总(细胞内和细胞外)MCYST产量增加(第一次实验)。此外，产生MCYST的野生型菌株及其mcyB突变体对抑制无机碳吸收的反应基本相同，可变荧光和藻蓝蛋白细胞配额增加，C-I，C-I缺乏率增加。然而，野生型的反应明显更强，还包括增加了叶绿素a细胞配额。这些差异表明该突变体适应低C-I、C-I条件的能力有限。我们的结论是，MCYSTs可能参与了提高蓝藻细胞中光合作用装置对波动的无机碳条件的适应效率。
Batch culture experiments with the cyanobacterium Microcystis aeruginosa PCC 7806 were performed in order to test the hypothesis that microcystins (MCYSTs) are produced in response to a relative deficiency of intracellular inorganic carbon (C-i,C-i). In the first experiment, MCYST production was studied under increased C-i,C-i deficiency conditions, achieved by restricting sodium-dependent bicarbonate uptake through replacement of sodium bicarbonate in the medium with its potassium analog. The same experimental approach was used in a second experiment to compare the response of the wild-type strain M. aeruginosa PCC 7806 with its mcyB mutant, which lacks the ability to produce MCYSTs. In a third experiment, the impact of varying the C-i,C-i status on MCYST production was examined without suppressing the sodium-dependent bicarbonate transporter; instead, a detailed investigation of a dark-light cycle was performed. In all experiments, a relative C-i,C-i deficiency was indicated by an elevated variable fluorescence signal and led to enhanced phycocyanin cell quotas. Higher MCYST cell quotas (in the first and third experiments) and increased total (intracellular plus extracellular) MCYST production (in the first experiment) were detected with increased C-i,C-i deficiency. Furthermore, the MCYST-producing wild-type strain and its mcyB mutant showed basically the same response to restrained inorganic carbon uptake, with elevated variable fluorescence and phycocyanin cell quotas with increased C-i,C-i deficiency. The response of the wild type, however, was distinctly stronger and also included elevated chlorophyll a cell quotas. These differences indicate the limited ability of the mutant to adapt to low-C-i,C-i conditions. We concluded that MCYSTs may be involved in enhancing the efficiency of the adaptation of the photosynthetic apparatus to fluctuating inorganic carbon conditions in cyanobacterial cells.