Objectives

Many bacterial species naturally take up DNA from their surroundings and recombine it into their chromosome through homologous gene transfer (HGT) to aid in survival and gain advantageous functions. Herein we present the first characterization of Type IV pili facilitated natural competence in Fusobacterium nucleatum, which is a Gram-negative, anaerobic bacterium that participates in a range of infections and diseases including periodontitis, preterm birth, and cancer.

Methods

Here we used bioinformatics on multiple Fusobacterium species, as well as molecular genetics to characterize natural competence in strain F. nucleatum subsp. nucleatum ATCC 23726.

Results

We bioinformatically identified components of the Type IV conjugal pilus machinery and show this is a conserved system within the Fusobacterium genus. We next validate Type IV pili in natural competence in F. nucleatum ATCC 23726 and show that gene deletions in key components of pilus deployment (pilQ) and cytoplasmic DNA import (comEC) abolish DNA uptake and chromosomal incorporation. We next show that natural competence may require native F. nucleatum DNA methylation to bypass restriction modification systems and allow subsequent genomic homologous recombination.

Conclusions

In summary, this proof of principle study provides the first characterization of natural competence in Fusobacterium nucleatum and highlights the potential to exploit this DNA import mechanism as a genetic tool to characterize virulence mechanisms of an opportunistic oral pathogen.

中文翻译：

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IV 型菌毛促进具核梭杆菌的自然能力

目标

许多细菌物种自然地从周围环境中获取 DNA，并通过同源基因转移 (HGT) 将其重组到染色体中，以帮助生存并获得有利的功能。在此，我们首次描述了 IV 型菌毛促进具核梭杆菌自然能力的特征，具核梭杆菌是一种革兰氏阴性厌氧细菌，参与一系列感染和疾病，包括牙周炎、早产和癌症。

方法

在这里，我们使用了多个梭杆菌属物种的生物信息学以及分子遗传学来表征菌株F. nucleatum subsp. 的自然能力。有核虫 ATCC 23726。

结果

我们通过生物信息学方法鉴定了 IV 型接合菌毛机制的组成部分，并表明这是梭杆菌属内的一个保守系统。接下来，我们在F. nucleatum ATCC 23726中验证了 IV 型菌毛的自然能力，并表明菌毛部署 ( pilQ)和细胞质 DNA 输入 ( comEC)关键组件中的基因缺失会消除 DNA 摄取和染色体掺入。接下来我们表明，自然能力可能需要天然具核梭菌DNA 甲基化来绕过限制性修饰系统并允许随后的基因组同源重组。

结论

总之，这项原理证明研究首次表征了具核梭杆菌的自然能力，并强调了利用这种 DNA 输入机制作为遗传工具来表征机会性口腔病原体毒力机制的潜力。