A hybrid experimental-modelling study of SOS response-induced filamentation and its effect on bacterial colony growth

细菌对抗生素的耐药性是一个全球性问题，已经与许多细菌感染造成的死亡有关。细菌可以通过DNA损伤诱导的SOS反应介导的突变进化出耐药性，这也导致DNA修复和细胞分裂抑制。虽然已知破坏DNA的抗生素和紫外线辐射可激活SOS反应，但其他非主要破坏DNA的杀菌抗生素是否能够诱导SOS反应仍未解决。sos诱导的细胞分裂抑制也导致细胞形态的变化，因为细胞变成丝状。在一些野生型细胞中，SOS反应是自发诱导的，导致细胞间突变和形态的变化。在这个项目中，我们提出了一种混合实验和建模的方法。利用单分子跟踪，我们将通过观察SOS调节因子LexA的浓度动态及其共蛋白酶RecA的表达来研究SOS对不同种类抗生素的反应。然后，我们将使用由LexA调节并编码细胞分裂抑制剂sulA的sulA的表达测量，以产生连接LexA动力学和细胞丝化表型的数学模型。最后，我们将使用微流体测量大肠杆菌在机械力下的弯曲，以及在进行成丝时的生长速率，并使用它来开发一个基于个体的细菌菌落生长的计算模型，实现成丝。然后，我们将使用该模型，结合标准微生物学实验，了解SOS异质性在群体尺度上的影响。

Bacterial resistance to antibiotics is a global problem which is already implicated in many deaths by bacterial infection. Bacteria can evolve resistance through mutations mediated by the DNA damage-induced SOS response, which also results in DNA repair and cell division inhibition. Whilst DNA-damaging antibiotics and UV radiation are known to activate the SOS response, it remains unresolved whether other, non-primarily DNA damaging bactericidal antibiotics are capable of inducing the SOS response. SOS-induced cell division inhibition also leads to changes in cell morphology as the cells become filamentous. In some wild type cells, the SOS response is spontaneously induced, leading to variations in mutations and morphology between cells. In this project, we propose a hybrid experimental and modelling approach. Using single molecule tracking, we will examine SOS responses to different kinds of antibiotics by looking at concentration dynamics of the SOS regulator LexA and expression of its coprotease RecA. We will then use measurements of expression of sulA, which is regulated by LexA and codes for the cell division inhibitor SulA, to produce a mathematical model linking LexA dynamics and the cell filamentation phenotype. Finally, we will take measurements of E. coli bending under mechanical forces using microfluidics, and growth rates when undergoing filamentation, and use this to develop an individual-based computational model of bacterial colony growth that implements filamentation. We will then use this model, combined with standard microbiology experiments, to understand the effect of SOS heterogeneity at the population scale.