Ecological drivers of intragenomic conflict resolution

经典的进化观是通过遗传给后代的突变逐渐积累微小变化的过程。然而，基因组测序显示，在细菌中，基因经常通过一种称为水平基因转移的过程在细胞和物种之间交换，从而使进化能够进行大而快的跳跃。基因经常通过被称为质粒的环状DNA片段从一个细菌细胞传递到另一个细菌细胞。然而，对细菌细胞来说，获得质粒会花费高昂，因为质粒会消耗能量，并引入新的基因来扰乱细菌的正常工作。在进化论中，这些成本被称为基因组内冲突，因为对质粒有利的东西对细菌染色体不利，反之亦然。我们最近已经证明，进化可以通过“补偿进化”的过程来解决这些冲突，即细菌染色体或质粒获得突变，从而降低携带质粒的成本。通过提高质粒存活率，补偿性进化可能会增加新基因从细菌染色体跳到质粒上的机会，从而使这些基因与群落中的其他物种共享。在这个提案中，我们将发现微生物群落的生态和他们所生活的环境如何塑造补偿进化的过程，以及补偿进化本身是否加速了物种之间的基因共享。

The classical view of evolution is as a process of gradual accumulation of small changes by mutations passed on to descendants. However, genome sequencing has revealed that in bacteria genes are frequently exchanged between cells and species by a process called horizontal gene transfer, allowing evolution to make big, fast jumps. Genes often pass from one bacterial cell to another on circular pieces of DNA called plasmids. However, acquiring a plasmid can be costly to a bacterial cell because plasmids use energy and introduce new genes that disrupt the normal working of the bacterium. In evolutionary theory these costs are called intragenomic conflicts because what is good for the plasmid is bad for the bacterial chromosome, and vice versa. We have recently shown that evolution can resolve these conflicts by a process of 'compensatory evolution', whereby either the bacterial chromosome or the plasmid gains mutations that lessen the cost of carrying the plasmid. By increasing plasmid survival, compensatory evolution is likely to increase the chance of new genes jumping onto plasmids from bacterial chromosomes, allowing these to be shared with other species in the community. In this proposal we will discover how the ecology of microbial communities and the environments they live in shape the processes of compensatory evolution, and whether compensatory evolution itself speeds up the sharing of genes between species.