Conservative sex and the benefits of transformation in Streptococcus pneumoniae.
Conservative sex and the benefits of transformation in Streptococcus pneumoniae.
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DOI：
10.1371/journal.ppat.1003758
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发表时间：
2013
期刊：
影响因子：
6.7
通讯作者：
Rozen DE
中科院分区：
文献类型：
--
作者：
Engelmoer DJ;Donaldson I;Rozen DE
自然转化对细菌基因组进化有重要影响，但维持这种细菌性别模式的进化因素仍不确定。假设转化对细菌具有积极和消极的进化影响。它可以通过将有益的突变结合到单个个体中来促进适应，或者通过将有害的等位基因暴露于自然选择来减少突变负荷。或者，它可能使转化的细胞暴露于受损或突变的环境DNA，并且在能量上是昂贵的。在这里，我们研究了长期的影响，在自然主管物种肺炎链球菌的野生型和竞争力缺陷菌株在恒化器中进化的人口为1000代。这些人群中的一半暴露于周期性的轻度压力，以检查转型的背景依赖性好处。我们发现，在良性条件下，能力降低健身增益，然而，这些成本降低周期性压力的存在。使用全基因组重测序，我们表明，有能力的人口固定较少的新突变和能力，防止出现的突变。我们的研究结果表明，在良性条件下的进化过程中，能力有助于维持基因组的稳定性，但进化代价高昂;然而，在压力期间，同样的保守主义使细胞能够在面对新突变时保持适应性，这首次表明转化的好处是依赖于环境的。环境DNA的转化可以为细菌提供一种快速适应不断变化的环境的方法。虽然这可以通过促进抗生素耐药性的传播而使微生物受益，但如果它导致群体中有益等位基因的丢失，它也可能是有害的。因此，目前还不清楚是什么进化因素使转化在细菌种群中持续存在。我们使用自然转化的机会致病菌肺炎链球菌来研究转化的长期益处。我们比较了S.经过1000代的进化，这些人口的一半是自然转化（主管），而另一半是缺乏这一功能。与此同时，一半的进化群体定期暴露于短期的轻度压力。我们发现，竞争力降低了进化种群的平均适应度增益，但这种成本在面临轻度压力的种群中有所减轻。使用全基因组测序，我们发现功能能力减少了固定突变的总数，并防止超突变细胞的频率增加。我们的研究结果表明，在S。肺炎是一个保守的过程，以保护等位基因，而不是一个创新的持续，因为它重组有益的突变。
Natural transformation has significant effects on bacterial genome evolution, but the evolutionary factors maintaining this mode of bacterial sex remain uncertain. Transformation is hypothesized to have both positive and negative evolutionary effects on bacteria. It can facilitate adaptation by combining beneficial mutations into a single individual, or reduce the mutational load by exposing deleterious alleles to natural selection. Alternatively, it may expose transformed cells to damaged or otherwise mutated environmental DNA and is energetically expensive. Here, we examine the long-term effects of transformation in the naturally competent species Streptococcus pneumoniae by evolving populations of wild-type and competence-deficient strains in chemostats for 1000 generations. Half of these populations were exposed to periodic mild stress to examine context-dependent benefits of transformation. We find that competence reduces fitness gain under benign conditions; however, these costs are reduced in the presence of periodic stress. Using whole genome re-sequencing, we show that competent populations fix fewer new mutations and that competence prevents the emergence of mutators. Our results show that during evolution in benign conditions competence helps maintain genome stability but is evolutionary costly; however, during periods of stress this same conservativism enables cells to retain fitness in the face of new mutations, showing for the first time that the benefits of transformation are context dependent. Transformation of environmental DNA can provide bacteria with a means to adapt quickly to a changing environment. While this can benefit microbes by facilitating the spread of antibiotic resistance, it can also be harmful if it causes the loss of beneficial alleles from a population. Therefore, it is unclear what evolutionary factors enable transformation to persist in bacterial populations. We used the naturally transformable opportunistic pathogen Streptococcus pneumoniae to investigate the long-term benefits of transformation. We compared the fitness of laboratory populations of S. pneumoniae after 1000 generations of evolution. Half of these populations were naturally transformable (competent) while the other half was deficient for this function. At the same time, half of the evolving populations were periodically exposed to short periods of mild stress. We find that competence reduces the average fitness gain of evolving populations, but this cost is mitigated in populations facing mild stress. Using whole genome sequencing, we discovered that functional competence reduces the total number of fixed mutations and prevents hyper-mutable cells from increasing in frequency. Our results suggest that competence in S. pneumoniae is a conservative process acting to preserve alleles, rather than an innovative one that persists because it recombines beneficial mutations.
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DOI：
10.1073/pnas.86.22.8842
发表时间：
1989-11-01
影响因子：
11.1
作者：
DOWSON, CG;HUTCHISON, A;SPRATT, BG
通讯作者：
SPRATT, BG
影响因子：
2.9
作者：
LENSKI, RE;ROSE, MR;TADLER, SC
通讯作者：
TADLER, SC
DOI：
10.1126/science.1182395
发表时间：
2010-01-22
期刊：
Science (New York, N.Y.)
影响因子：
--
作者：
Harris SR;Feil EJ;Holden MT;Quail MA;Nickerson EK;Chantratita N;Gardete S;Tavares A;Day N;Lindsay JA;Edgeworth JD;de Lencastre H;Parkhill J;Peacock SJ;Bentley SD
通讯作者：
Bentley SD
影响因子：
1.4
作者：
ESHEL I;FELDMAN M W
通讯作者：
FELDMAN M W
影响因子：
3.3
作者：
Baltrus, David A.;Guillemin, Karen;Phillips, Patrick C.
通讯作者：
Phillips, Patrick C.