Honma Kiyonobu, Ruscitto Angela, Frey Andrew M, Stafford Graham P, Sharma Ashu
Dept. of Oral Biology, University at Buffalo, Buffalo, NY, United States.
Oral & Maxillofacial Pathology, The University of Sheffield, Sheffield, United Kingdom.
Microb Pathog. 2016 May;94:12-20. doi: 10.1016/j.micpath.2015.08.012. Epub 2015 Aug 28.
Tannerella forsythia is a periodontal pathogen implicated in periodontitis. This gram-negative pathogen depends on exogenous peptidoglycan amino sugar N-acetylmuramic acid (NAM) for growth. In the biofilm state the bacterium can utilize sialic acid (Neu5Ac) instead of NAM to sustain its growth. Thus, the sialic acid utilization system of the bacterium plays a critical role in the growth and survival of the organism in the absence of NAM. We sought the function of a T. forsythia gene annotated as nanT coding for an inner-membrane sugar transporter located on a sialic acid utilization genetic cluster. To determine the function of this putative sialic acid transporter, an isogenic nanT-deletion mutant generated by allelic replacement strategy was evaluated for biofilm formation on NAM or Neu5Ac, and survival on KB epithelial cells. Moreover, since T. forsythia forms synergistic biofilms with Fusobacterium nucleatum, co-biofilm formation activity in mixed culture and sialic acid uptake in culture were also assessed. The data showed that the nanT-inactivated mutant of T. forsythia was attenuated in its ability to uptake sialic acid. The mutant formed weaker biofilms compared to the wild-type strain in the presence of sialic acid and as co-biofilms with F. nucleatum. Moreover, compared to the wild-type T. forsythia nanT-inactivated mutant showed reduced survival when incubated on KB epithelial cells. Taken together, the data presented here demonstrate that NanT-mediated sialic transportation is essential for sialic acid utilization during biofilm growth and survival of the organism on epithelial cells and implies sialic acid might be key for its survival both in subgingival biofilms and during infection of human epithelial cells in vivo.
福赛斯坦纳菌是一种与牙周炎相关的牙周病原体。这种革兰氏阴性病原体的生长依赖于外源性肽聚糖氨基糖N - 乙酰胞壁酸（NAM）。在生物膜状态下，该细菌可以利用唾液酸（Neu5Ac）替代NAM来维持其生长。因此，该细菌的唾液酸利用系统在缺乏NAM的情况下对其生长和存活起着关键作用。我们探究了福赛斯坦纳菌中一个注释为nanT的基因的功能，该基因编码位于唾液酸利用基因簇上的一种内膜糖转运蛋白。为了确定这种假定的唾液酸转运蛋白的功能，通过等位基因替换策略产生的同基因nanT缺失突变体，被评估了在NAM或Neu5Ac上形成生物膜的能力以及在KB上皮细胞上的存活能力。此外，由于福赛斯坦纳菌与具核梭杆菌形成协同生物膜，还评估了混合培养中的共生物膜形成活性以及培养物中唾液酸的摄取情况。数据表明，福赛斯坦纳菌的nanT失活突变体摄取唾液酸的能力减弱。与野生型菌株相比，该突变体在有唾液酸存在时形成的生物膜较弱，与具核梭杆菌形成的共生物膜也较弱。此外，与野生型福赛斯坦纳菌相比，nanT失活突变体在KB上皮细胞上孵育时存活能力降低。综上所述，此处呈现的数据表明，NanT介导的唾液酸转运对于生物膜生长过程中唾液酸的利用以及该生物体在上皮细胞上的存活至关重要，这意味着唾液酸可能是其在龈下生物膜中以及体内感染人类上皮细胞期间存活的关键因素。
