最近的研究表明,包括口腔链球菌在内的相关物种的表型和代谢异质性,一种典型的口腔共生细菌,变形链球菌,一种致龋细菌,和戈顿链球菌,在牙周病生物膜中起辅助病原体的作用。在这项研究中,确定了口腔卫生良好的个体唾液中含有的代谢物,之后,确定的益生元候选物的影响,D-塔格糖,在表型上,基因表达,并研究了这三种关键细菌的代谢谱。对18名全身健康志愿者的唾液代谢组进行的检查发现,唾液D-塔格糖与口腔中较低的牙齿生物膜丰度有关(Spearman相关系数;r=-0.603,p=0.008),然后体外分析D-塔格糖对口腔链球菌的影响。在含有D-塔格糖作为唯一碳水化合物来源的化学成分确定的培养基(CDM)中,S.mutans和S.gordonii各自显示出可忽略的生物膜形成,而在口腔链球菌培养物中形成了显著的生物膜。此外,即使在葡萄糖的存在下,S.mutans和gordonii以D-塔格糖浓度依赖性方式显示生长抑制和最终活细胞计数降低。相比之下,未观察到D-塔格糖对口腔链球菌生长的抑制作用。为了研究D-塔格糖的物种特异性抑制作用,D-塔格糖处理的变形链球菌的代谢组学概况,S.Gordonii,并检查口腔链球菌细胞。变形链球菌和戈顿链球菌中丙酮酸衍生氨基酸的细胞内数量,但在口腔沙门氏菌中没有,如支链氨基酸和丙氨酸,在D-塔格糖的存在下倾向于降低。这种现象表明D-塔格糖通过影响糖酵解及其下游代谢来抑制这些细菌的生长。总之,本研究提供了D-塔格糖在口腔健康良好的个体唾液中含量丰富的证据。此外,实验结果表明D-塔格糖选择性地抑制口腔病原体变形链球菌和戈顿链球菌的生长。相比之下,口腔共生S.oralis似乎受到了可忽略的影响,因此强调了D-塔格糖作为口服益生元的潜力,因为它能够操纵那些靶向口服链球菌的代谢。
Recent studies have shown phenotypic and metabolic heterogeneity in related species including Streptococcus oralis, a typical oral commensal bacterium, Streptococcus mutans, a cariogenic bacterium, and Streptococcus gordonii, which functions as an accessory pathogen in periodontopathic biofilm. In this study, metabolites characteristically contained in the saliva of individuals with good oral hygiene were determined, after which the effects of an identified prebiotic candidate, D-tagatose, on phenotype, gene expression, and metabolic profiles of those three key bacterial species were investigated. Examinations of the saliva metabolome of 18 systemically healthy volunteers identified salivary D-tagatose as associated with lower dental biofilm abundance in the oral cavity (Spearman\'s correlation coefficient; r = -0.603, p = 0.008), then the effects of D-tagatose on oral streptococci were analyzed in vitro. In chemically defined medium (CDM) containing D-tagatose as the sole carbohydrate source, S. mutans and S. gordonii each showed negligible biofilm formation, whereas significant biofilms were formed in cultures of S. oralis. Furthermore, even in the presence of glucose, S. mutans and S. gordonii showed growth suppression and decreases in the final viable cell count in a D-tagatose concentration-dependent manner. In contrast, no inhibitory effects of D-tagatose on the growth of S. oralis were observed. To investigate species-specific inhibition by D-tagatose, the metabolomic profiles of D-tagatose-treated S. mutans, S. gordonii, and S. oralis cells were examined. The intracellular amounts of pyruvate-derived amino acids in S. mutans and S. gordonii, but not in S. oralis, such as branched-chain amino acids and alanine, tended to decrease in the presence of D-tagatose. This phenomenon indicates that D-tagatose inhibits growth of those bacteria by affecting glycolysis and its downstream metabolism. In conclusion, the present study provides evidence that D-tagatose is abundant in saliva of individuals with good oral health. Additionally, experimental results demonstrated that D-tagatose selectively inhibits growth of the oral pathogens S. mutans and S. gordonii. In contrast, the oral commensal S. oralis seemed to be negligibly affected, thus highlighting the potential of administration of D-tagatose as an oral prebiotic for its ability to manipulate the metabolism of those targeted oral streptococci.