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首页> 美国卫生研究院文献>Applied and Environmental Microbiology >Physiological Events in Clostridium acetobutylicum during the Shift from Acidogenesis to Solventogenesis in Continuous Culture and Presentation of a Model for Shift Induction
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Physiological Events in Clostridium acetobutylicum during the Shift from Acidogenesis to Solventogenesis in Continuous Culture and Presentation of a Model for Shift Induction

机译：连续培养中从产酸向溶剂生成转变过程中丙酮丁醇梭菌的生理事件和转变诱导模型的提出

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The pH of continuous cultures of Clostridium acetobutylicum growing at pH 5.6 was allowed to decrease to 4.3 after acid production and thereby to shift the cultures from acetate and butyrate to acetone and butanol formation. Several parameters were determined during the shift. An increase in the intracellular acid concentration to 440 mM was recorded. An excess of undissociated butyric acid but not of acetic acid just before the shift to solventogenesis was followed by a decline in acid production and subsequently by the uptake of acids. The intracellular ATP concentration reached a minimum before the onset of solventogenesis; this presumably reflects the ATP-consuming proton extrusion connected with the increase in the ΔpH from 0.7 to 1.4 units. The pool of NADH plus NADPH exhibited a drastic increase until solventogenesis was induced. The changes in the ATP and ADP and NADH plus NADPH pools during these pH shift experiments were the beginning of a stable metabolic oscillation which could also be recorded as an oscillation of the culture redox potential under steady-state solventogenic conditions. Similar changes were observed when the shift was induced by the addition of butyrate and acetate (50 mM each) to the continuous culture. However, when methyl viologen was added, important differences were found: ATP levels did not reach a minimum, acetoacetate decarboxylase activity could not be measured, and butanol but not acetone was produced. A model for the shift is proposed; it assumes the generation of two signals, one by the changed ATP and ADP levels and the other by the increased NAD(P)H level.
机译：在产酸后，使在pH 5.6下生长的丙酮丁醇梭菌连续培养物的pH降低至4.3，从而将培养物从乙酸盐和丁酸盐转变为丙酮和丁醇的形成。在换班期间确定了几个参数。记录到细胞内酸浓度增加到440mM。紧接向溶剂生成之前，过量的未离解的丁酸而不是乙酸，随后是产酸量下降，随后是酸的吸收。在溶剂生成开始之前，细胞内ATP浓度达到最低；这大概反映了ATP消耗的质子挤压与ΔpH从0.7单位增加到1.4单位有关。 NADH加NADPH的库显示出急剧增加，直到诱导溶剂生成为止。在这些pH转换实验过程中，ATP和ADP，NADH和NADPH池的变化是稳定的代谢振荡的开始，也可以记录为稳态溶剂生成条件下培养物氧化还原电位的振荡。当通过向连续培养物中添加丁酸盐和乙酸盐（各50 mM）诱导转变时，观察到类似的变化。但是，当添加甲基紫精时，发现了重要的区别：ATP水平未达到最低要求，乙酰乙酸酯脱羧酶活性无法测量，丁醇但未生成丙酮。提出了转变的模型；它假定生成了两个信号，一个是通过更改ATP和ADP的水平，另一个是通过增加NAD（P）H的水平。

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