Data from: Competence increases survival during stress in Streptococcus pneumoniae.

Horizontal gene transfer mediated by transformation is of central importance in bacterial evolution. However, numerous questions remain about the maintenance of processes that underlie transformation. Most hypotheses for the benefits of transformation focus on what bacteria might do with DNA, but ignore the important fact that transformation is subsumed within the broader process of competence. Accordingly, the apparent benefits of transformation might rely less on recombination than on other potential benefits associated with the broader suite of traits regulated by competence. We examined the importance of this distinction in the naturally competent species Streptococcus pneumoniae, focussing specifically on predictions of the DNA-for-repair hypothesis. We confirm earlier results in other naturally competent species that transformation protects against DNA-damaging stress. In addition, we show that the stress-protection extends to non-DNA-damaging stress. More important, we find that for some forms of stress transformation is not required for cells to benefit from the induction of competence. This rejects the narrowly defined DNA-for-repair hypotheses and provides the first support for Claverys’ hypothesis that competence, but not necessarily transformation, may act as a general process to relieve stress. Our results highlight the need to distinguish benefits of transformation from broader benefits of competence that do not rely on DNA uptake and recombination.

以自然转化（transformation）介导的水平基因转移（Horizontal gene transfer）在细菌演化中具有核心意义。然而，关于自然转化背后相关过程的维持机制，仍存在诸多待解问题。现有关于自然转化益处的多数假说，均聚焦于细菌可利用DNA完成的生理过程，却忽略了一个关键事实：自然转化本就隶属于更宽泛的感受态（competence）调控过程范畴。因此，自然转化所展现出的益处，或许并非主要依赖同源重组（recombination），而是更多与感受态调控的一系列性状相关的其他潜在益处有关。我们以天然具备感受态的肺炎链球菌（Streptococcus pneumoniae）为研究对象，探讨这一区分的重要性，并重点验证了DNA修复假说的相关预测。我们证实了此前在其他天然感受态物种中的研究结果：自然转化可帮助细菌抵御DNA损伤型胁迫。此外，我们还发现，这种胁迫防护效应同样适用于非DNA损伤型胁迫。更关键的是，我们发现，针对部分类型的胁迫，细菌在受益于感受态诱导时，并不需要依赖自然转化过程。这一结果否定了狭义层面的DNA修复假说，并首次为Claverys假说提供了实证支持：即感受态（而非必然依赖自然转化）可作为一种通用的胁迫缓解过程。本研究结果凸显了区分自然转化的益处与不依赖DNA摄取和同源重组的感受态广谱益处的必要性。