Natural competence is a major mechanism for horizontal DNA transfer in the oral pathogen Porphyromonas gingivalis.
Natural competence is a major mechanism for horizontal DNA transfer in the oral pathogen Porphyromonas gingivalis.
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作者：
Tribble GD;Rigney TW;Dao DH;Wong CT;Kerr JE;Taylor BE;Pacha S;Kaplan HB
牙龈卟啉单胞菌是一种革兰氏阴性厌氧菌，仅存在于人类口腔中。牙龈卟啉单胞菌的长期定植需要细菌逃避宿主的免疫反应，同时适应不断变化的宿主生理和口腔微生物群组成的变化。牙龈卟啉单胞菌的遗传多样性似乎反映了其栖息地的变异性；然而，人们对产生这种多样性的分子机制知之甚少。此前，我们的研究小组确定染色体 DNA 转移发生在牙龈卟啉单胞菌菌株之间。在本研究中，我们研究了假定的 DNA 转移基因在接合和转化中的作用，并证明由 comF 介导的自然能力是染色体 DNA 转移的主要形式，通过类接合机制进行的转移发挥次要作用。我们的结果表明，天然能力机制存在于多种牙龈卟啉单胞菌菌株中，并且 DNA 摄取对 DNA 来源或修饰状态不敏感。此外，首次在牙龈卟啉单胞菌生物膜中观察到细胞外 DNA，并预测其是菌株之间水平转移和等位基因交换的主要 DNA 来源。我们认为，牙菌斑生物膜中通过类转化过程进行的 DNA 交换对于牙龈卟啉单胞菌在充满挑战的口腔环境中的生存和持久存在具有重要的生态重要性。 牙龈卟啉单胞菌定植于全世界人类的口腔中。这些细菌的长期存在会导致慢性牙周炎和与牙齿脱落相关的宿主发病。牙龈卟啉单胞菌是一种遗传多样性的物种，这种变异性被认为有助于其在不同人类宿主中成功定殖和生存，以及逃避宿主免疫防御和免疫策略。我们在此确定自然能力是牙龈卟啉单胞菌 DNA 交换背后的主要驱动力，而接合 DNA 转移则发挥次要作用。此外，我们首次揭示了牙龈卟啉单胞菌生物膜中存在细胞外 DNA，这很可能是牙菌斑内菌株之间交换 DNA 的来源。这些研究扩展了我们对人类口腔菌群这一重要成员将其与宿主的关系从共生关系转变为致病关系的机制的理解。
Porphyromonas gingivalis is a Gram-negative anaerobe that resides exclusively in the human oral cavity. Long-term colonization by P. gingivalis requires the bacteria to evade host immune responses while adapting to the changing host physiology and alterations in the composition of the oral microflora. The genetic diversity of P. gingivalis appears to reflect the variability of its habitat; however, little is known about the molecular mechanisms generating this diversity. Previously, our research group established that chromosomal DNA transfer occurs between P. gingivalis strains. In this study, we examine the role of putative DNA transfer genes in conjugation and transformation and demonstrate that natural competence mediated by comF is the dominant form of chromosomal DNA transfer, with transfer by a conjugation-like mechanism playing a minor role. Our results reveal that natural competence mechanisms are present in multiple strains of P. gingivalis, and DNA uptake is not sensitive to DNA source or modification status. Furthermore, extracellular DNA was observed for the first time in P. gingivalis biofilms and is predicted to be the major DNA source for horizontal transfer and allelic exchange between strains. We propose that exchange of DNA in plaque biofilms by a transformation-like process is of major ecological importance in the survival and persistence of P. gingivalis in the challenging oral environment. P. gingivalis colonizes the oral cavities of humans worldwide. The long-term persistence of these bacteria can lead to the development of chronic periodontitis and host morbidity associated with tooth loss. P. gingivalis is a genetically diverse species, and this variability is believed to contribute to its successful colonization and survival in diverse human hosts, as well as evasion of host immune defenses and immunization strategies. We establish here that natural competence is the major driving force behind P. gingivalis DNA exchange and that conjugative DNA transfer plays a minor role. Furthermore, we reveal for the first time the presence of extracellular DNA in P. gingivalis biofilms, which is most likely the source of DNA exchanged between strains within dental plaque. These studies expand our understanding of the mechanisms used by this important member of the human oral flora to transition its relationship with the host from a commensal to a pathogenic relationship.