UCLA School of Dentistry, 10833 Le Conte Avenue, CHS 20-114, Los Angeles, CA 90095-1668, USA.
Microb Ecol. 2012 Apr;63(3):532-42. doi: 10.1007/s00248-011-9989-2. Epub 2011 Dec 28.
The development of multispecies oral microbial communities involves complex intra- and interspecies interactions at various levels. The ability to adhere to the resident bacteria or the biofilm matrix and overcome community resistance are among the key factors that determine whether a bacterium can integrate into a community. Fusobacterium nucleatum is a prevalent Gram-negative oral bacterial species that is able to adhere to a variety of oral microbes and has been implicated in playing an important role in the establishment of multispecies oral microbial community. However, the majority of experiments thus far has focused on the physical adherence between two species as measured by in vitro co-aggregation assays, while the community-based effects on the integration of F. nucleatum into multispecies microbial community remains to be investigated. In this study, we focus on community integration of F. nucleatum. We demonstrated using an established in vitro mice oral microbiota (O-mix) that the viability of F. nucleatum was significantly reduced upon addition to the O-mix due to cell contact-dependent induction of hydrogen peroxide (H(2)O(2)) production by oral community. Interestingly, this inhibitory effect was significantly alleviated when F. nucleatum was allowed to adhere to its known interacting partner species (such as Streptococcus sanguinis) prior to addition. Furthermore, this aggregate formation-dependent protection was absent in the F. nucleatum mutant strain ΔFn1526 that is unable to bind to a number of Gram-positive species. More importantly, this protective effect was also observed during integration of F. nucleatum into a human salivary microbial community (S-mix). These results suggest that by adhering to other oral microbes, F. nucleatum is able to mask the surface components that are recognized by H(2)O(2) producing oral community members. This evasion strategy prevents detection by antagonistic oral bacteria and allows integration into the developing oral microbial community.
多物种口腔微生物群落的发展涉及到各种水平的复杂种内和种间相互作用。能够黏附到常驻细菌或生物膜基质上并克服群落抗性是决定细菌能否整合到群落中的关键因素之一。具核梭杆菌是一种普遍存在的革兰氏阴性口腔细菌，能够黏附多种口腔微生物，并被认为在建立多物种口腔微生物群落中发挥着重要作用。然而，迄今为止的大多数实验都集中在通过体外共聚集测定来测量两种细菌之间的物理黏附，而关于具核梭杆菌整合到多物种微生物群落中的群落效应仍有待研究。在本研究中，我们专注于具核梭杆菌的群落整合。我们通过建立的体外小鼠口腔微生物群（O-mix）证明，由于口腔群落中细胞接触依赖性诱导的过氧化氢（H₂O₂）产生，具核梭杆菌的活力在添加到 O-mix 中后显著降低。有趣的是，当具核梭杆菌在添加前允许与已知的相互作用伙伴物种（如血链球菌）黏附时，这种抑制作用会显著减轻。此外，这种聚集形成依赖性保护在无法与多种革兰氏阳性物种结合的 Fn1526 缺失突变株中不存在。更重要的是，在具核梭杆菌整合到人类唾液微生物群落（S-mix）中时也观察到了这种保护作用。这些结果表明，通过黏附到其他口腔微生物，具核梭杆菌能够掩盖被过氧化氢产生的口腔群落成员识别的表面成分。这种逃避策略可以防止被拮抗口腔细菌检测，并允许其整合到正在发育的口腔微生物群落中。
