Bacillus subtilis metabolism and energetics in carbon-limited and excess-carbon chemostat culture
Bacillus subtilis metabolism and energetics in carbon-limited and excess-carbon chemostat culture
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DOI：
10.1128/jb.183.24.7308-7317.2001
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发表时间：
2001-12-01
影响因子：
3.2
通讯作者：
Sauer, U
中科院分区：
文献类型：
--
作者：
Dauner, M;Storni, T;Sauer, U
与在葡萄糖限制下生长的培养物相比，在葡萄糖过量下生长的培养物中微生物生长的能量效率显著降低，但是不同能量耗散过程导致效率降低的程度目前还不清楚。我们在这里介绍了一个新的概念，用于平衡的总细胞能量通量的基础上转换成能量当量的能量和碳通量，我们将这一概念应用于葡萄糖，氨，和磷酸盐限制恒化培养核黄素生产枯草芽孢杆菌。基于[U-C-13（6）]葡萄糖标记实验和代谢通量分析，在生长缓慢、葡萄糖限制的B.枯草芽孢杆菌几乎专门分配在维持代谢和生物质形成。相反，在过量葡萄糖培养物中，主要通过溢流代谢来实现前体和后体的解偶联，而两个量化的无效酶循环和代谢转移到能量效率较低的途径是可以忽略的。在大多数文化中，总能量通量的约20%不能被分配给特定的能量消耗过程，因此可能被目前未被考虑的离子泄漏等过程耗散。与葡萄糖或氨限制的培养物相反，代谢通量分析显示磷酸盐限制的B中的三羧酸（TCA）循环通量较低。枯草芽孢杆菌，这是一致的CcpA依赖性的分解代谢物抑制的循环和/或转录激活的基因参与溢出代谢的存在下，过量的葡萄糖。体内酶活性的ATP依赖性控制似乎与观察到的TCA循环通量差异无关。
The energetic efficiency of microbial growth is significantly reduced in cultures growing under glucose excess compared to cultures growing under glucose limitation, but the magnitude to which different energy-dissipating processes contribute to the reduced efficiency is currently not well understood. We introduce here a new concept for balancing the total cellular energy flux that is based on the conversion of energy and carbon fluxes into energy equivalents, and we apply this concept to glucose-, ammonia-, and phosphate-limited chemostat cultures of riboflavin-producing Bacillus subtilis. Based on [U-C-13(6)] glucose-labeling experiments and metabolic flux analysis, the total energy flux in slow-growing, glucose-limited B. subtilis is almost exclusively partitioned in maintenance metabolism and biomass formation. In excess-glucose cultures, in contrast, uncoupling of anabolism and catabolism is primarily achieved by overflow metabolism, while two quantified futile enzyme cycles and metabolic shifts to energetically less efficient pathways are negligible. In most cultures, about 20% of the total energy flux could not be assigned to a particular energy-consuming process and thus are probably dissipated by processes such as ion leakage that are not being considered at present. In contrast to glucose- or ammonia-limited cultures, metabolic flux analysis revealed low tricarboxylic acid (TCA) cycle fluxes in phosphate-limited B. subtilis, which is consistent with CcpA-dependent catabolite repression of the cycle and/or transcriptional activation of genes involved in overflow metabolism in the presence of excess glucose. ATP-dependent control of in vivo enzyme activity appears to be irrelevant for the observed differences in TCA cycle fluxes.