Tanzer J M, Grant L, Thompson A, Li L, Rogers J D, Haase E M, Scannapieco F A
School of Dental Medicine, University of Connecticut Health Center, Farmington, CT 06030-1605, USA.
School of Dental Medicine, University at Buffalo, Buffalo, NY, USA.
Microbiology (Reading). 2003 Sep;149(Pt 9):2653-2660. doi: 10.1099/mic.0.26022-0.
Streptococcus gordonii produces two alpha-amylase-binding proteins, AbpA and AbpB, that have been extensively studied in vitro. Little is known, however, about their significance in oral colonization and cariogenicity (virulence). To clarify these issues, weanling specific pathogen-free Osborne-Mendel rats, TAN : SPFOM(OM)BR, were inoculated either with wild-type strains FAS4-S or Challis-S or with strains having isogenic mutations of abpA, abpB, or both, to compare their colonization abilities and persistence on the teeth. Experiments were done with rats fed a sucrose-rich diet containing low amounts of starch or containing only starch. The mutants and wild-types were quantified in vivo and carious lesions were scored. In 11 experiments, S. gordonii was a prolific colonizer of the teeth when rats were fed the sucrose (with low starch)-supplemented diet, often dominating the flora. Sucrose-fed rats had several-fold higher recoveries of inoculants than those eating the sucrose-free, starch-supplemented diet, regardless of inoculant type. The strain defective in AbpB could not colonize teeth of starch-only-eating rats, but could colonize rats if sucrose was added to the diet. Strains defective in AbpA surprisingly colonized better than their wild-types. A double mutant deficient in both AbpA and AbpB (abpA/abpB) colonized like its wild-type. Wild-types FAS4-S and Challis-S had no more than marginal cariogenicity. Notably, in the absence of AbpA, cariogenicity was slightly augmented. Both the rescue of colonization by the AbpB- mutant and the augmentation of colonization by AbpA- mutant in the presence of dietary sucrose suggested additional amylase-binding protein interactions relevant to colonization. Glucosyltransferase activity was greater in mutants defective in abpA and modestly increased in the abpB mutant. It was concluded that AbpB is required for colonization of teeth of starch-eating rats and its deletion is partially masked if rats eat a sucrose-starch diet. AbpA appears to inhibit colonization of the plaque biofilm in vivo. This unexpected effect in vivo may be associated with interaction of AbpA with glucosyltransferase or with other colonization factors of these cells. These data illustrate that the complex nature of the oral environment may not be adequately modelled by in vitro systems.
戈登氏链球菌可产生两种α-淀粉酶结合蛋白，即AbpA和AbpB，这两种蛋白已在体外得到广泛研究。然而，对于它们在口腔定植和致龋性（毒力）方面的意义却知之甚少。为阐明这些问题，我们将断奶的无特定病原体的奥斯本-孟德尔大鼠（TAN : SPFOM(OM)BR）接种野生型菌株FAS4-S或Challis-S，或接种具有abpA、abpB或两者同基因缺失突变的菌株，以比较它们的定植能力和在牙齿上的存留情况。实验使用喂食富含低淀粉量蔗糖饮食或仅含淀粉饮食的大鼠进行。对突变体和野生型进行体内定量，并对龋损进行评分。在11项实验中，当给大鼠喂食添加蔗糖（低淀粉）的饮食时，戈登氏链球菌是牙齿的大量定植菌，常占菌群主导地位。无论接种菌类型如何，喂食蔗糖的大鼠对接种菌的回收率比食用无蔗糖、添加淀粉饮食的大鼠高出几倍。AbpB缺陷型菌株不能在只吃淀粉的大鼠牙齿上定植，但如果在饮食中添加蔗糖则可以在大鼠牙齿上定植。令人惊讶的是，AbpA缺陷型菌株比其野生型定植得更好。AbpA和AbpB双缺陷型突变体（abpA/abpB）的定植情况与其野生型相似。野生型FAS4-S和Challis-S的致龋性仅为轻微。值得注意的是，在没有AbpA的情况下，致龋性略有增强。在饮食中有蔗糖存在时，AbpB突变体的定植恢复以及AbpA突变体的定植增强表明存在与定植相关的额外淀粉酶结合蛋白相互作用。在abpA缺陷型突变体中葡糖基转移酶活性更高，而在abpB突变体中适度增加。得出的结论是，AbpB是吃淀粉大鼠牙齿定植所必需的，如果大鼠食用蔗糖-淀粉饮食，其缺失会被部分掩盖。AbpA似乎在体内抑制菌斑生物膜的定植。这种体内的意外效应可能与AbpA与葡糖基转移酶或这些细胞的其他定植因子的相互作用有关。这些数据表明，体外系统可能无法充分模拟口腔环境的复杂性。
