PGA exopolysaccharide in biofilm formation and pathogenicity of Aggregatibacter a

描述（由申请人提供）：放线菌聚集菌（Aa）和几种病原菌附着在非生物表面上，并产生胞外多糖，将细菌细胞固定在这些定植表面上。 Aa 产生的胞外多糖是 β-1,6-连接的 N-乙酰基-D-葡萄糖胺 (GlcNAc) 单元的均聚物。 Aa 利用与大肠杆菌的 pga、鼠疫耶尔森菌的 hms 和表皮葡萄球菌的 ica 同源的四基因操纵子产生这种胞外多糖 (PGA)。在Aa中，操纵子pgaABCD携带由pgaB编码的脱乙酰酶(EC 3.5.1.41)。我们的初步数据表明，PgaB 酶能够去除 PGA 的 GlcNAc 上的乙酰基。更有趣的是，我们发现当添加到生长培养基中时，PgaB 会分离预先形成的生物膜并抑制 Aa、胸膜肺炎放线杆菌和表皮葡萄球菌的生物膜形成。我们之前已经证明，同样来自 Aa 的酶分散素 B (DspB) 可通过 PGA 解聚来防止几种革兰氏阴性和革兰氏阳性细菌的表面附着。与 DspB 不同，新发现的酶 PgaB 是 PGA 中 GlcNAc 残基的脱乙酰酶，通过脱乙酰作用改变 PGA 的电荷状态（正电荷富集）。这种酶活性表明分离/抑制机制可能是通过增加 PGA 聚合物上的排斥相互作用来实现的。重要的是，在这些生物体中，尤其是在 Aa 中，脱乙酰化在生物膜去除或形成中的作用尚未得到充分研究。我们将使用 Aa 的 PgaB 作为模型系统来理解这些过程。我们的长期目标是了解 PGA 在 Aa 致病性中的作用以及 PgaB 的脱乙酰酶活性如何在该作用中发挥核心作用。我们将使用体外和体内模型来验证 PGA 在 Aa 毒力中发挥关键作用的总体假设。具体而言，将研究以下目标： 具体目标 1. 证明酶 PgaB 的 PGA 脱乙酰能力对其抗生物膜活性至关重要。具体目标 2a。证明 PGA 乙酰化的状态和程度有助于 Aa 中生物膜的形成。具体目标 2b。证明胞外多糖 PGA 有助于 Aa 致病性。

DESCRIPTION (provided by applicant): Aggregatibacter actinomycetemcomitans (Aa) and several pathogenic bacteria attach to abiotic surfaces and produce exopolysaccharide that immobilize the bacterial cells on these colonized surfaces. The exopolysaccharide produced by Aa is a homopolymer of ¿-1,6-linked N-acetyl-D-glucosamine (GlcNAc) units. Aa produces this exopolysaccharide (PGA) utilizing a four-gene operon homologous to the pga of Escherichia coli, hms of Yersinia pestis, and ica of Staphylococcus epidermidis. In Aa, the operon pgaABCD carries a deacetylase enzyme (EC 3.5.1.41) encoded by pgaB. Our Preliminary Data show that the enzyme PgaB has the ability to remove acetyl groups from GlcNAc of PGA. More intriguingly, we discovered that PgaB detaches preformed biofilms and inhibits biofilm formation of Aa, Actinobacillus pleuropneumoniae and S. epidermidis when added to the growth medium. We have previously shown that an enzyme dispersin B (DspB) also from Aa prevents the surface attachment of several Gram negative as well as Gram-positive bacterial species through depolymerization of PGA. Unlike DspB, the newly discovered enzyme PgaB is a deacetylase of GlcNAc residues in PGA and through deacetylation alters the charge state of PGA (enrichment of positive charges). This enzyme activity suggests that the mechanism of detachment/inhibition might be through the increased repulsive interactions on the PGA polymer. Importantly, the role of deacetylation in biofilm removal or formation is understudied in these organisms, especially in Aa. We will use PgaB from Aa as a model system to understand these processes. Our long-range goal is to understand the role of PGA in Aa pathogenicity and how the deacetylase activity of PgaB is central to this role. We will use both in vitro as well as in vivo models to tet the overall hypothesis that PGA plays a critical role in Aa virulence. Specifically, the following aims will be studied: Specific Aim 1. Demonstrate that PGA deacetylating ability of the enzyme PgaB is critical for its antibiofilm activity. Specific Aim 2a. Demonstrate that the status and degree of acetylation of PGA contributes to the biofilm formation in Aa. Specific Aim 2b. Demonstrate that the exopolysaccharide PGA contributes to Aa pathogenicity.