Lieder Sarah, Jahn Michael, Seifert Jana, von Bergen Martin, Müller Susann, Takors Ralf
Institute for Biochemical Engineering, University of Stuttgart, Allmandring 31, Stuttgart, Germany.
Department of Environmental Microbiology, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, Leipzig, 04318, Germany.
AMB Express. 2014 Aug 29;4:71. doi: 10.1186/s13568-014-0071-6. eCollection 2014.
Population heterogeneity occurring in industrial microbial bioprocesses is regarded as a putative effector causing performance loss in large scale. While the existence of subpopulations is a commonly accepted fact, their appearance and impact on process performance still remains rather unclear. During cell cycling, distinct subpopulations differing in cell division state and DNA content appear which contribute individually to the efficiency of the bioprocess. To identify stressed or impaired subpopulations, we analyzed the interplay of growth rate, cell cycle and phenotypic profile of subpopulations by using flow cytometry and cell sorting in conjunction with mass spectrometry based global proteomics. Adjusting distinct growth rates in chemostats with the model strain Pseudomonas putida KT2440, cells were differentiated by DNA content reflecting different cell cycle stages. The proteome of separated subpopulations at given growth rates was found to be highly similar, while different growth rates caused major changes of the protein inventory with respect to e.g. carbon storage, motility, lipid metabolism and the translational machinery. In conclusion, cells in various cell cycle stages at the same growth rate were found to have similar to identical proteome profiles showing no significant population heterogeneity on the proteome level. In contrast, the growth rate clearly determines the protein composition and therefore the metabolic strategy of the cells.
工业微生物生物过程中出现的群体异质性被认为是导致大规模生产性能损失的一个假定因素。虽然亚群体的存在是一个普遍公认的事实，但它们的出现及其对过程性能的影响仍相当不清楚。在细胞周期中，会出现细胞分裂状态和DNA含量不同的独特亚群体，它们各自对生物过程的效率有贡献。为了识别受胁迫或受损的亚群体，我们通过使用流式细胞术和细胞分选技术，并结合基于质谱的全局蛋白质组学，分析了亚群体的生长速率、细胞周期和表型特征之间的相互作用。使用模式菌株恶臭假单胞菌KT2440在恒化器中调整不同的生长速率，细胞根据反映不同细胞周期阶段的DNA含量进行区分。发现在给定生长速率下分离出的亚群体的蛋白质组高度相似，而不同的生长速率会导致蛋白质库在例如碳储存、运动性、脂质代谢和翻译机制等方面发生重大变化。总之，发现在相同生长速率下处于不同细胞周期阶段的细胞具有相似乃至相同的蛋白质组图谱，在蛋白质组水平上没有明显的群体异质性。相比之下，生长速率明显决定了细胞的蛋白质组成，进而决定了细胞的代谢策略。
