Sex and Death: testing the evolutionary benefit of recombination using a bacterium and bacteriophage model

性与死亡：使用细菌和噬菌体模型测试重组的进化益处

基本信息

批准号：
NE/K000926/1
负责人：
Michiel Vos
金额：
$ 10.18万
依托单位：
UNIVERSITY OF EXETER
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FK000926%2F1
关键词：
Sex Death testing evolutionary benefit

项目摘要

General SummaryBackgroundAlthough bacteria reproduce through binary fission, they are not purely clonal. On occasion, they are capable of taking up DNA from the environment derived from other bacterial cells and recombine it with their own genetic material. This process is termed transformation. Just as in plant and animal sex, this shuffling of DNA increases the genetic variation in the population. The process of natural selection needs such genetic variation in the population to be able to select the fittest individuals. Populations of organisms that engage in sex (or more generally recombination) could thus be assumed to adapt more quickly to their environment. However, recombination is only favoured when the environment is ever-changing. If not, recombination would eventually disassemble the fittest combinations of DNA it had created. The strongest candidate for both strong and continuously fluctuating selection is that of parasite attack. Parasites and hosts are locked in a continuing arms race: hosts develop resistance against their parasites, and parasites evolve to overcome this resistance and so on and so forth. This scenario is named 'the Red Queen Hypothesis' after Lewis Carroll's book Through the Looking-Glass, where the Red Queen tells Alice: 'It takes all the running you can do, to keep in the same place'. AimThe Red Queen Hypothesis is especially likely to be applicable to bacteria for two reasons. First, bacteria are frequently attacked by deadly viruses (bacteriophages), exerting very strong selection for novel resistance. Second, bacterial recombination is 'cheaper' than that of many plants and animals. For instance, bacteria do not rely on sex for reproduction and could resort to it only when needed. Although a lot of theory has been developed, experimental tests of the Red Queen Hypothesis are rare. Here, we propose to experimentally coevolve the aquatic bacterium Aeromonas, known to frequently recombine, with phage. The quality of free DNA available for transformation will be experimentally manipulated. This will allow us to for the first time quantify whether 'bacterial sex' can aid adaptation to parasitic viruses. Transformation results in the reshuffling of all polymorphisms in the population, not only those associated with resistance to phage. We therefore will also include a temperature treatment where high, stressful temperature requires additional adaptation with an expected greater potential benefit of recombination. Applications and BenefitsBacteria and phage are an ideal model system to test the Red Queen Hypothesis, but are also of great importance to human health and the economy. Various Aeromonas species are opportunistic pathogens causing a wide range of infections. Aeromonas is a pathogen on the rise and has been found to be the most common cause of soft tissue and skin infections in a study on survivors of the 2004 tsunami in Asia. Bacteriophages are important agents of bacterial mortality. With increasing levels of bacterial resistance to antibiotics, phage therapy has received renewed interest as an alternative strategy to prevent and fight infection by using phages as 'evolving antibiotics'. Importantly, this project will test whether coevolution with phage selects for increased transformation. Phage therapy designed to limit the negative impact of pathogenic bacteria thus could actually result in the increased capability of bacteria to evolve virulence or antibiotic resistance through transformation. Finding any increased benefit of recombination at higher temperature could have important implications for evolutionary change in response to climate change. This will be the first study explicitly linking phage coevolution and transformation, two main evolutionary forces in microbiology, and is bound to yield exciting new insights with special relevance to fighting an opportunistic pathogen.

一般摘要背景虽然细菌通过二元裂变繁殖，但它们并不是纯粹的克隆。有时，它们能够从环境中获取其他细菌细胞的 DNA，并将其与自身的遗传物质重组。这个过程称为转变。正如植物和动物的性行为一样，DNA 的这种改组增加了种群的遗传变异。自然选择的过程需要种群中的这种遗传变异才能选择最适应的个体。因此，可以假设进行性行为（或更普遍的重组）的生物体种群能够更快地适应其环境。然而，只有当环境不断变化时，重组才会受到青睐。如果不是这样，重组最终会分解它所创造的最合适的 DNA 组合。强烈且持续波动的选择的最强候选者是寄生虫攻击。寄生虫和宿主陷入了一场持续的军备竞赛：宿主对其寄生虫产生抵抗力，而寄生虫则进化以克服这种抵抗力，等等。这种情况被命名为“红皇后假说”，源自刘易斯·卡罗尔的《爱丽丝镜中奇遇记》一书，其中红皇后告诉爱丽丝：“你需要尽全力奔跑，才能保持在同一个地方”。目的红皇后假说特别可能适用于细菌，原因有两个。首先，细菌经常受到致命病毒（噬菌体）的攻击，对新的耐药性产生非常强的选择。其次，细菌重组比许多植物和动物的重组“便宜”。例如，细菌不依赖性进行繁殖，只有在需要时才会诉诸性。尽管已经发展了很多理论，但红皇后假说的实验测试却很少。在这里，我们建议通过实验使已知经常重组的水生细菌气单胞菌与噬菌体共同进化。可用于转化的游离 DNA 的质量将通过实验进行控制。这将使我们能够首次量化“细菌性”是否有助于适应寄生病毒。转化导致群体中所有多态性的重新洗牌，而不仅仅是那些与噬菌体抗性相关的多态性。因此，我们还将包括一种温度处理，其中高压力温度需要额外的适应，以期获得更大的重组潜在益处。应用和优点细菌和噬菌体是检验红皇后假说的理想模型系统，而且对人类健康和经济也非常重要。各种气单胞菌属都是机会致病菌，可引起广泛的感染。气单胞菌是一种呈上升趋势的病原体，在一项针对 2004 年亚洲海啸幸存者的研究中发现，气单胞菌是软组织和皮肤感染的最常见原因。噬菌体是细菌死亡的重要因素。随着细菌对抗生素的耐药性水平不断提高，噬菌体疗法作为一种通过使用噬菌体作为“进化抗生素”来预防和对抗感染的替代策略再次受到人们的关注。重要的是，该项目将测试与噬菌体的共同进化是否会选择增加转化。因此，旨在限制病原菌负面影响的噬菌体疗法实际上可以提高细菌通过转化进化出毒力或抗生素耐药性的能力。发现更高温度下重组带来的任何增加的好处可能会对响应气候变化的进化变化产生重要影响。这将是第一项明确将噬菌体共同进化和转化（微生物学中的两种主要进化力量）联系起来的研究，并且必将产生令人兴奋的新见解，与对抗机会性病原体特别相关。

项目成果

期刊论文数量（3）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

No effect of natural transformation on the evolution of resistance to bacteriophages in the Acinetobacter baylyi model system.

DOI：
10.1038/srep37144
发表时间：
2016-11-21
期刊：
Scientific reports
影响因子：
4.6
作者：
McLeman A;Sierocinski P;Hesse E;Buckling A;Perron G;Hülter N;Johnsen PJ;Vos M
通讯作者：
Vos M

A barrier to homologous recombination between sympatric strains of the cooperative soil bacterium Myxococcus xanthus.