Oral Health CRC, Melbourne Dental School, Bio21 Institute, The University of Melbourne, Melbourne, Victoria, Australia.
Biological Optical Microscopy Platform, Faculty of Medicine, Dentistry & Health Sciences, The University of Melbourne, Melbourne, Victoria, Australia.
J Bacteriol. 2021 Apr 21;203(10). doi: 10.1128/JB.00631-20.
, a bacterial pathogen contributing to human periodontitis, exports and anchors cargo proteins to its surface, enabling the production of black pigmentation using a type IX secretion system (T9SS) and conjugation to anionic lipopolysaccharide (A-LPS). To determine whether T9SS components need to be assembled for correct secretion and A-LPS modification of cargo proteins, combinations of nonpigmented mutants lacking A-LPS or a T9SS component were mixed to investigate in complementation. Reacquisition of pigmentation occurred only between an A-LPS mutant and a T9SS mutant, which coincided with A-LPS modification of cargo proteins detected by Western blotting and coimmunoprecipitation/quantitative mass spectrometry. Complementation also occurred using an A-LPS mutant mixed with outer membrane vesicles (OMVs) or purified A-LPS. Fluorescence experiments demonstrated that OMVs can fuse with and transfer lipid to , leading to the conclusion that complementation of T9SS function occurred through A-LPS transfer between cells. None of the two-strain crosses involving only the five T9SS OM component mutants produced black pigmentation, implying that the OM proteins cannot be transferred in a manner that restores function and surface pigmentation, and hence, a more ordered temporal assembly of T9SS components may be required. Our results show that LPS can be transferred between cells or between cells and OMVs to complement deficiencies in LPS biosynthesis and hemin-related pigmentation to reveal a potentially new mechanism by which the oral microbial community is modulated to produce clinical consequences in the human host. is a keystone pathogen contributing to periodontitis in humans, leading to tooth loss. The oral microbiota is essential in this pathogenic process and changes from predominantly Gram-positive (health) to predominantly Gram-negative (disease) species. uses its type IX secretion system (T9SS) to secrete and conjugate virulence proteins to anionic lipopolysaccharide (A-LPS). This study investigated whether components of this secretion system could be complemented and found that it was possible for A-LPS biosynthetic mutants to be complemented in both by strains that had the A-LPS on the cell surface and by exogenous sources of A-LPS. This is the first known example of LPS exchange in a human bacterial pathogen which causes disease through complex microbiota-host interactions.
牙龈卟啉单胞菌是一种导致人类牙周炎的细菌病原体，它通过 9 型分泌系统（T9SS）将货物蛋白输出并锚定在其表面，利用该系统和与阴离子脂多糖（A-LPS）的共轭作用来产生黑色色素。为了确定 T9SS 组件是否需要组装才能正确分泌和修饰货物蛋白的 A-LPS，将缺乏 A-LPS 或 T9SS 组件的非色素突变体混合在一起进行互补。仅在 A-LPS 突变体和 T9SS 突变体之间重新获得了色素，这与 Western blot 和共免疫沉淀/定量质谱检测到的货物蛋白的 A-LPS 修饰相吻合。用 A-LPS 突变体与外膜囊泡（OMVs）或纯化的 A-LPS 混合也能进行互补。荧光实验表明，OMVs 可以融合并将脂质转移到 ，得出结论，T9SS 功能的互补是通过细胞间 A-LPS 的转移来实现的。涉及仅五个 T9SS OM 组件突变体的两菌株杂交均未产生黑色色素，这意味着 OM 蛋白不能以恢复功能和表面色素沉着的方式转移，因此，T9SS 组件的更有序的时间组装可能是必需的。我们的结果表明，LPS 可以在细胞间或细胞与 OMVs 间转移，以补充 LPS 生物合成和血红素相关色素沉着的缺陷，从而揭示了一种新的机制，即口腔微生物群落可以通过这种机制进行调节，从而在人类宿主中产生临床后果。 是一种导致人类牙周炎的关键病原体，会导致牙齿脱落。口腔微生物群在这个致病过程中是必不可少的，它从主要的革兰氏阳性（健康）转变为主要的革兰氏阴性（疾病）物种。 使用其 9 型分泌系统（T9SS）将毒力蛋白分泌并连接到阴离子脂多糖（A-LPS）上。本研究调查了该分泌系统的组件是否可以互补，并发现表面有 A-LPS 的菌株和外源性 A-LPS 来源都可以互补 A-LPS 生物合成突变体。这是第一个已知的在导致疾病的人类细菌病原体中发生 LPS 交换的例子，该疾病是通过复杂的微生物群-宿主相互作用引起的。
