Identifying Low pH Active and Lactate-Utilizing Taxa within Oral Microbiome Communities from Healthy Children Using Stable Isotope Probing Techniques

<div><h3>Background</h3><p>Many human microbial infectious diseases including dental caries are polymicrobial in nature. How these complex multi-species communities evolve from a healthy to a diseased state is not well understood. Although many health- or disease-associated oral bacteria have been characterized <em>in vitro</em>, their physiology within the complex oral microbiome is difficult to determine with current approaches. In addition, about half of these species remain uncultivated to date with little known besides their 16S rRNA sequence. Lacking culture-based physiological analyses, the functional roles of uncultivated species will remain enigmatic despite their apparent disease correlation. To start addressing these knowledge gaps, we applied a combination of Magnetic Resonance Spectroscopy (MRS) with RNA and DNA based Stable Isotope Probing (SIP) to oral plaque communities from healthy children for <em>in vitro</em> temporal monitoring of metabolites and identification of metabolically active and inactive bacterial species.</p> <h3>Methodology/Principal Findings</h3><p>Supragingival plaque samples from caries-free children incubated with ¹³C-substrates under imposed healthy (buffered, pH 7) and diseased states (pH 5.5 and pH 4.5) produced lactate as the dominant organic acid from glucose metabolism. Rapid lactate utilization upon glucose depletion was observed under pH 7 conditions. SIP analyses revealed a number of genera containing cultured and uncultivated taxa with metabolic capabilities at pH 5.5. The diversity of active species decreased significantly at pH 4.5 and was dominated by <em>Lactobacillus</em> and <em>Propionibacterium</em> species, both of which have been previously found within carious lesions from children.</p> <h3>Conclusions/Significance</h3><p>Our approach allowed for identification of species that metabolize carbohydrates under different pH conditions and supports the importance of Lactobacilli and Propionibacterium in the development of childhood caries. Identification of species within healthy subjects that are active at low pH can lead to a better understanding of oral caries onset and generate appropriate targets for preventative measures in the early stages.</p> </div

Quel avenir pour les relations turco-américaines?

Remarques préliminaires : Ce guide élaboré par des praticiens de DDE décrit la démarche de gestion de projet en s'appuyant sur les différentes étapes chronologiques de l'opération et en précise les éléments clefs.En ce qui concerne les stations d'épuration, le cadre technique et réglementaire fixé par la Loi sur l'Eau est maintenant relativement bien défini . Certaines évolutions sont cependant attendues : révision duC .C.T.G. fascicule 81 titre Il, normalisation européenne.Par contre le fondement juridique de l' intervention des services de l' Etat pour le compte des collectivités locales est, a la date d'achèvement de ce guide, en plein remaniement.Le lecteur devra donc veiller à tenir compte des textes réglementaires ou normatifs ultérieurs,la construction et l'exploitation de station d'épuration doivent répondre à des exigences de plus en plus fortes, notamment en ce qui concerne la fiabilité . Ces exigences requièrent une gestion rigoureuse des projets. Le guide précise les recommandations essentielles aux divers stades de l'opération : prise de commande, procédures administratives, financement, études préalables, ordonnancement,dossiers techniques, suivi de chantier (lien avec l'exploitation, qualité, sécurité et protection de la santé),réception des travaux