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.

通过转化（transformation）介导的水平基因转移（horizontal gene transfer）在细菌进化中具有核心重要性。然而，关于转化背后核心过程的维持机制，目前仍存在诸多未解问题。现有关于转化益处的多数假说，均聚焦于细菌可利用DNA完成的功能，却忽略了一个关键事实：转化本身隶属于更广泛的感受态（competence）过程范畴。据此，转化所表现出的益处，或许更多源于感受态调控的一系列广谱性状所带来的潜在收益，而非依赖基因重组（recombination）。我们以天然感受态物种肺炎链球菌（Streptococcus pneumoniae）为研究对象，针对这一区分的重要性展开验证，并特别聚焦于"DNA用于修复（DNA-for-repair）"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得到的研究结果：转化可抵御DNA损伤性胁迫。此外，我们发现该胁迫防护效应可延伸至非DNA损伤性胁迫。更为关键的是，我们发现针对部分类型的胁迫，细胞无需通过转化即可借助感受态诱导获得防护收益。这一结果否定了狭义的"DNA用于修复"假说，并首次为克莱弗里（Claverys）假说提供了实证支持：感受态（而非必然依赖转化）可作为缓解胁迫的通用过程发挥作用。我们的研究结果强调，亟需区分转化的专属益处与不依赖DNA摄取和基因重组的感受态广谱益处。