The competence pili of transformable Gram-positive species form a subset of the diverse and widespread class of extracellular filamentous organelles known as type IV pili (T4P). In Gram-negative bacteria, T4P act through dynamic cycles of extension and retraction to carry out diverse activities including attachment, motility, protein secretion, and DNA uptake. It remains unclear whether T4P in Gram-positive species exhibit this same dynamic activity, and their mechanism of action for DNA uptake remains unclear. They are hypothesized to either (1) passively form transient cavities in the cell wall to facilitate DNA passage, (2) act as static adhesins to enrich DNA near the cell surface for subsequent uptake by membrane-embedded transporters, or (3) play an active role in translocating bound DNA via their dynamic activity. Here, using a recently described pilus labeling approach, we demonstrate that pneumococcal competence pili are highly dynamic structures that rapidly extend and retract from the cell surface. By labeling ComGC with bulky adducts, we further demonstrate that pilus retraction is essential for natural transformation. Together, our results indicate that Gram-positive type IV competence pili are dynamic and retractile structures that play an active role in DNA uptake.

中文翻译：

---

肺炎链球菌的IV型能力菌毛是高度动态的结构，可回缩以促进DNA的吸收

可转化的革兰氏阳性菌种的能力菌毛形成了被称为IV型菌毛（T4P）的多种多样的细胞外丝状细胞器的子集。在革兰氏阴性细菌中，T4P通过伸展和收缩的动态循环起作用，以执行各种活动，包括附着，运动，蛋白质分泌和DNA吸收。革兰氏阳性菌中的T4P是否表现出同样的动态活性尚不清楚，它们对DNA摄取的作用机理仍不清楚。据推测，它们是（1）在细胞壁上被动形成瞬时空腔以促进DNA传递；（2）充当静态粘附素，使细胞表面附近的DNA富集，随后被膜包埋的转运蛋白摄取；或（3）发挥通过其动态活性在转运结合的DNA中发挥积极作用。这里，使用最近描述的菌毛标记方法，我们证明肺炎球菌能力菌毛是高度动态的结构，可以从细胞表面快速延伸和缩回。通过用大体积的加合物标记ComGC，我们进一步证明菌毛回缩对于自然转化至关重要。总之，我们的结果表明，革兰氏阳性IV型能力菌毛是动态的和可伸缩的结构，在DNA摄取中起积极作用。