Agnello M, Cen L, Tran N C, Shi W, McLean J S, He X
1 School of Dentistry, University of California at Los Angeles, Los Angeles, CA, USA.
2 School of Dentistry, Department of Periodontics, University of Washington, Seattle, WA, USA.
J Dent Res. 2017 Jul;96(8):924-930. doi: 10.1177/0022034517707512. Epub 2017 May 9.
Dental caries can be described as a dysbiosis of the oral microbial community, in which acidogenic, aciduric, and acid-adapted bacterial species promote a pathogenic environment, leading to demineralization. Alkali generation by oral microbes, specifically via arginine catabolic pathways, is an essential factor in maintaining plaque pH homeostasis. There is evidence that the use of arginine in dentifrices helps protect against caries. The aim of the current study was to investigate the mechanistic and ecological effect of arginine treatment on the oral microbiome and its regulation of pH dynamics, using an in vitro multispecies oral biofilm model that was previously shown to be highly reflective of the in vivo oral microbiome. Pooled saliva from 6 healthy subjects was used to generate overnight biofilms, reflecting early stages of biofilm maturation. First, we investigated the uptake of arginine by the cells of the biofilm as well as the metabolites generated. We next explored the effect of arginine on pH dynamics by pretreating biofilms with 75 mM arginine, followed by the addition of sucrose (15 mM) after 0, 6, 20, or 48 h. pH was measured at each time point and biofilms were collected for 16S sequencing and targeted arginine quantification, and supernatants were prepared for metabolomic analysis. Treatment with only sucrose led to a sustained pH drop from 7 to 4.5, while biofilms treated with sucrose after 6, 20, or 48 h of preincubation with arginine exhibited a recovery to higher pH. Arginine was detected within the cells of the biofilms, indicating active uptake, and arginine catabolites citrulline, ornithine, and putrescine were detected in supernatants, indicating active metabolism. Sequencing analysis revealed a shift in the microbial community structure in arginine-treated biofilms as well as increased species diversity. Overall, we show that arginine improved pH homeostasis through a remodeling of the oral microbial community.
龋齿可被描述为口腔微生物群落的生态失调，其中产酸、耐酸和适应酸性环境的细菌种类会促进致病环境的形成，导致脱矿质作用。口腔微生物产生碱，特别是通过精氨酸分解代谢途径产生碱，是维持菌斑pH值稳态的一个重要因素。有证据表明，在牙膏中使用精氨酸有助于预防龋齿。本研究的目的是使用一种体外多物种口腔生物膜模型来研究精氨酸处理对口腔微生物群的作用机制和生态效应及其对pH动态变化的调节，该模型先前已被证明能高度反映体内口腔微生物群。使用6名健康受试者的混合唾液生成过夜生物膜，以反映生物膜成熟的早期阶段。首先，我们研究了生物膜细胞对精氨酸的摄取以及产生的代谢产物。接下来，我们通过用75 mM精氨酸预处理生物膜，然后在0、6、20或48小时后添加蔗糖（15 mM），探讨了精氨酸对pH动态变化的影响。在每个时间点测量pH值，并收集生物膜进行16S测序和靶向精氨酸定量，制备上清液进行代谢组学分析。仅用蔗糖处理导致pH值从7持续下降到4.5，而在与精氨酸预孵育6、20或48小时后用蔗糖处理的生物膜显示pH值恢复到更高水平。在生物膜细胞内检测到精氨酸，表明有主动摄取，在上清液中检测到精氨酸分解代谢产物瓜氨酸、鸟氨酸和腐胺，表明有活跃的代谢。测序分析显示，经精氨酸处理的生物膜中微生物群落结构发生了变化，物种多样性也增加了。总体而言，我们表明精氨酸通过重塑口腔微生物群落改善了pH值稳态。
