Collective membrane potential dynamics in bacterial colonies

枯草芽孢杆菌的结构化种群通过电子通讯来协调它们的代谢。目前，尚不清楚其他细菌物种是否与它们的电化学行为同步。我们发现，在淋球菌形成的球形菌落中，细菌在中心超极化，随后，超极化的细胞壳径向菌落的外围移动。这种超极化之后是菌落中心的去极化。在这个提议中，我们旨在发现超极化的触发因素，超极化的集体传播机制，以及它与生长停滞的关系，以及对种群适应度的相关影响。具体地说，我们将把菌落中心的生长停滞与膜电位联系起来。为此，我们将结合我们最近建立的具有时空分辨率的生长速度表征方法和表征膜电位的工具。然后，我们旨在研究超极化的两个可能的触发因素。我们将评估氧气或营养物质的耗尽是否会导致超极化。此外，我们将检验这样一种假设，即在菌落中心积累的机械压力限制了生长并导致超极化。我们将通过调节菌落中淋球菌之间的吸引力来改变压力。诱惑力将通过对4型菌毛进行基因改造来调整，并以激光镊子为特征。最后，我们将讨论超极化传播是否需要细胞间通信的问题。为此，我们将研究不同群体结构中超极化波的时空动力学。从长远来看，重要的是确定导致超极化的离子通道，并解决膜电位集体变化的适合性影响。

Structured populations of Bacillus subtilis coordinate their metabolism by electrical communication. Currently, it is unknown, whether other bacterial species synchronize their electrochemical behavior. We found that within spherical colonies formed by Neisseria gonorrhoeae, bacteria hyperpolarize at the center and subsequently, a shell of hyperpolarized cells travels radially towards the periphery of the colony. This hyperpolarization is followed by depolarization at the colony center. In this proposal, we aim at discovering triggers for hyperpolarization, the mechanism of collective propagation of hyperpolarization, and its relation to growth arrest and related consequences on population fitness. Specifically, we will correlate growth arrest at the colony center with membrane potential. To this end, we will combine our recently established method for characterizing the growth rate with spatio-temporal resolution with tools for characterizing the membrane potential. Then, we aim at investigating two putative triggers of hyperpolarization. We will assess whether depletion of oxygen or a nutrient causes hyperpolarization. Furthermore, we will test the hypothesis that build-up of mechanical pressure at the center of the colony limits growth and causes hyperpolarization. We will vary the pressure by tuning the attractive force between gonococci in the colony. Attractive forces will be tuned by genetically modifying type 4 pili and characterized by laser tweezers. Finally, we will address the question whether cell-to-cell communication is required for the propagation of hyperpolarization. To this end, we will investigate the spatio-temporal dynamics of the hyperpolarization wave in different colony structures. In the long term, it will be important to identify the ion channels responsible for hyperpolarization and to address the fitness effects of collective changes in membrane potential.