Role of Dispersin B in the colonization and virulence of Aggregatibacter actinomycetemcomitans

ABS束 伴生放线杆菌(AA)和其他细菌附着在生物和非生物表面，并 产生胞外多糖，用来固定这些定植表面的细菌细胞 形成生物膜基质。AA产生的胞外多糖是N-乙酰-D-D-的均聚物。 含b-1，6-连接单元的氨基葡萄糖(GlcNAc)(简称PGA)。在生物膜生长过程中，要克服 与人口过剩相关的饥饿，细胞必须从表面分散到远端表面，从而 进一步殖民。这种释放的AA细胞的运动是由分散素B的水解性作用促进的 (DspB)，一种由AA产生的酶，它释放包裹在生物膜基质中的细胞。该产品 在PGA水解的过程中，GlcNAc存在于成熟的生物膜周围，可能成为AA和 其他邻近的细菌。在许多细菌共同栖息的多物种生物膜中，AA通过以下方式获得营养 定位在共生细菌戈登链球菌(Sg)附近。在这种情况下，AA可以利用 Sg为其生长所产生的乳酸，它是一种首选的碳源。为了保持Sg的存在 在其附近，作为回报，AA通过DspB的作用向邻近的Sg提供GlcNAc PGA。由于GlcNAc是Sg的首选碳源，这两种细菌都可以通过进入一种营养 合作，在这种合作中，双方都对在该利基地区持续殖民具有优势。应当指出的是， 细菌之间的互惠或合作的交叉喂养在生物膜中是受欢迎的(2)。我们的假设是1) PGA来源的GlcNAc，而不是外源GlcNAc，对AA在 与Sg的生物膜和代谢交叉喂养关系；2)DspB是AA毒力所必需的。我们会 用以下具体目标来检验这些假设： 具体目标1：a)证明DspB对于AA在生物膜生长模式下的生存是必不可少的。 B)证明Dspb对于维持交叉喂养关系是必不可少的 与Sg.合作进行营养交换。 具体目的2：研究DspB在口腔内AA定植和毒力中的作用。

Abs tract Aggregatibacter actinomycetemcomitans (Aa) and other bacteria attach to biotic and abiotic surfaces and produce exopolysaccharides, which are used to immobilize the bacterial cells on these colonized surfaces forming a biofilm matrix. The exopolysaccharide produced by Aa is a homopolymer of N-acetyl-D- glucosamine (GlcNAc) with b-1,6-linked units (abbreviated as PGA). During biofilm growth, to overcome starvation associated with overpopulation, cells must disperse from a surface to move to distal surfaces to colonize further. This movement of released cells of Aa is facilitated by the hydrolytic action of Dispersin B (DspB), an enzyme produced by Aa, which releases cells that are enmeshed in the biofilm matrix. The product of PGA hydrolysis, GlcNAc, is present around the mature biofilm and could become a nutrient for Aa and other neighboring bacteria. In a multispecies biofilm where many bacteria co-habitat, Aa gains nutrients by positioning itself near the commensal bacterium, Streptococcus gordonii (Sg). In this scenario, Aa can utilize the lactate produced by Sg, a preferred carbon source, for its growth. In order to maintain the presence of Sg in its vicinity, in reciprocation, Aa supplies the neighboring Sg with GlcNAc through the action of DspB on PGA. Since GlcNAc is a preferred carbon source for Sg, both bacteria can survive by entering into a nutritional co-operation wherein both have an advantage for persistent colonization in the niche. It should be noted that mutualistic or cooperative cross-feeding between bacteria is favored in biofilms (2). Our hypothesis is that 1) PGA-derived GlcNAc, not exogenous GlcNAc, is important for the survival and colonization of Aa in the biofilm and metabolic cross-feeding relationship with Sg; 2) DspB is required for the virulence of Aa. We will test these hypotheses with the following Specific Aims: Specific Aim 1: a) Demonstrate that DspB is essential for the survival of Aa in a biofilm mode of growth. b) Demonstrate that DspB is essential to maintain the cross-feeding relationship and cooperative nutrient exchange with Sg. Specific Aim 2: Characterize the role of DspB in the colonization and virulence of Aa in the oral cavity.