Interaction of prophages and colicin Ib at the single cell and population-wide level

大肠杆菌素是大肠杆菌产生的细菌素，对大肠杆菌有毒性。大肠杆菌及其近亲。大肠杆菌素被认为是克隆细菌种群中分工或劳动的经典例子。它们作为生产者群体的公共产品，但仅由一小部分群体合成，这些群体在大肠杆菌素释放后死亡。我们研究了大肠杆菌素Ib（ColIb），由人类致病性沙门氏菌肠道SV。鼠伤寒沙门氏菌（S. Tm）在单细胞水平上进行。我们证实，ColIb是在某些条件下，由一小部分的人口，至少部分裂解和释放ColIb。到那时，ColIb的释放机制尚不清楚。特异性溶素，如已知的其他大肠杆菌素，在ColIb的情况下不存在。我们在该优先计划第一个供资期的工作在温带、亚热带和ColIb之间建立了新的联系。我们发现，不同的类胡萝卜素原噬菌体或其裂解基因的存在与增加的ColIb释放到S。Tm培养上清液。这表明缺乏自身特异性溶素的ColIb可以寄生于温带真菌的溶素基因，并释放到环境中。在第二个资助期，我们现在的目标是进一步研究在单细胞水平上的大肠杆菌素生物学以及细菌的适应性和大肠杆菌素生产作为合作性状的进化的意义。生成适当的S。我们追求以下目标。首先，我们将研究在噬菌体介导的宿主裂解过程中，除了ColIb之外是否还释放其他大肠杆菌素。第二，我们假设原噬菌体在表达ColIb（cib）的同一亚群中优先被激活。TM.因此，这部分表达cib的细菌裂解以释放ColIb。我们将测试这一想法，通过分析ColIb（CIB）的表达和激活的温带类风湿关节炎在单细胞水平上使用荧光蛋白报告，微流体和实时显微镜。最后，我们将集中在模拟三方的相互作用，宿主细菌，大肠杆菌素和温带和测试，如果这是一个进化稳定的战略。为此，我们将采用体外实验和数学建模相结合的方法。

Colicins are bacteriocins produced by and toxic for E. coli and close relatives. Colicins are regarded as classical example of division or labor in clonal bacterial populations. They serve as public good for the population of producers but are synthesized by only a fraction of the population, which die upon colicin release. We studied the regulation of colicin Ib (ColIb), produced by a human pathogenic Salmonella enterica sv. Typhimurium strain (S. Tm) at the single cell level using gfp-reporters. We confirmed that ColIb is under certain conditions made by a fraction of the population which, at least in part lyse and release ColIb. By then, the release mechanism for ColIb was unknown. Specific lysins, as they are known for other colicins, are absent in the case of ColIb. Our work in the first funding period of this Priority Programme established a new link between temperate, lambdoid phages and ColIb. We show that the presence of different lambdoid prophages or their lysis genes correlates with increased ColIb release into the S. Tm culture supernatant. This suggests that ColIb, which lacks its own specific lysin, can parasitize lysis genes of temperate phages to be released in the environment. In the second funding period, we now aim to further investigate the significance of temperate phages for colicin biology at the single cell level as well as for bacterial fitness and evolution of colicin production as cooperative trait. Generating the appropriate S. Tm mutant- and reporter-strains we pursue the following objectives. First, we will investigate if other colicins besides ColIb are also released in the course of phage-mediated host lysis. Second, we assume that the prophage(s) will be preferentially activated within the same subset of ColIb (cib)-expressing S. Tm. Thereby, this part of the cib-expressing bacteria lyses in order to release ColIb. We will test this idea by analysing ColIb (cib)-expression and activation of temperate lambdoid phages at the single cell level using fluorescent protein reporters, microfluidics and real-time microscopy. Lastly we will focus on modeling the tripartite interaction of host bacteria, colicins and temperate phages and test if whether this is an evolutionary stable strategy. To this end, we will use by a combination of in vitro experiments and mathematical modeling.