School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China.
Cells. 2020 Feb 8;9(2):391. doi: 10.3390/cells9020391.
The processes involved in cell growth are extremely complicated even for a single cell organism such as , while the relationship between growth rate and cell size is simple. We aimed to reveal the systematic link between them from the aspect of the genome-scale metabolic network. Since the growth rate reflects metabolic rates of bacteria and the cell size relates to phospholipid synthesis, a part of bacterial metabolic networks, we calculated the cell length from the cardiolipin synthesis rate, where the cardiolipin synthesis reaction is able to represent the phospholipid metabolism of in the exponential growth phase. Combined with the flux balance analysis, it enables us to predict cell length and to examine the quantitative relationship between cell length and growth rate. By simulating bacteria growing in various nutrient media with the flux balance analysis and calculating the corresponding cell length, we found that the increase of the synthesis rate of phospholipid, the cell width, and the protein fraction in membranes caused the increase of cell length with growth rate. Different tendencies of phospholipid synthesis rate changing with growth rate result in different relationships between cell length and growth rate. The effects of gene deletions on cell size and growth rate are also examined. Knocking out the genes, such as Δ , Δ , Δ , Δ , and Δ , affects growth rate largely while affecting cell length slightly. Results of this method are in good agreement with experiments.
即使对于像 这样的单细胞生物，细胞生长所涉及的过程也极其复杂，而生长速率与细胞大小之间的关系却很简单。我们旨在从基因组代谢网络的角度揭示它们之间的系统联系。由于生长速率反映了细菌的代谢速率，而细胞大小与磷脂合成有关，磷脂是细菌代谢网络的一部分，我们从心磷脂合成速率计算了细胞长度，其中心磷脂合成反应能够代表指数生长阶段 中的磷脂代谢。结合通量平衡分析，它使我们能够预测细胞长度，并检验细胞长度与生长速率之间的定量关系。通过用通量平衡分析模拟在各种营养培养基中生长的细菌，并计算相应的细胞长度，我们发现磷脂合成率、细胞宽度和膜中蛋白质分数的增加导致细胞长度随生长速率增加。不同的磷脂合成率随生长速率变化的趋势导致细胞长度与生长速率之间的不同关系。还检查了基因缺失对细胞大小和生长速率的影响。敲除基因，如 Δ 、Δ 、Δ 、Δ 、和 Δ ，会极大地影响生长速率，而对细胞长度的影响则较小。该方法的结果与实验结果非常吻合。
