Carbohydrate Metabolism Is Essential for the Colonization of Streptococcus thermophilus in the Digestive Tract of Gnotobiotic Rats

Streptococcus thermophilus is the archetype of lactose-adapted bacterium and so far, its sugar metabolism has been mainly investigated in vitro. The objective of this work was to study the impact of lactose and lactose permease on S. thermophilus physiology in the gastrointestinal tract (GIT) of gnotobiotic rats. We used rats mono-associated with LMD-9 strain and receiving 4.5% lactose. This model allowed the analysis of colonization curves of LMD-9, its metabolic profile, its production of lactate and its interaction with the colon epithelium. Lactose induced a rapid and high level of S. thermophilus in the GIT, where its activity led to 49 mM of intra-luminal L-lactate that was related to the induction of mono-carboxylic transporter mRNAs (SLC16A1 and SLC5A8) and p27Kip1 cell cycle arrest protein in epithelial cells. In the presence of a continuous lactose supply, S. thermophilus recruited proteins involved in glycolysis and induced the metabolism of alternative sugars as sucrose, galactose, and glycogen. Moreover, inactivation of the lactose transporter, LacS, delayed S. thermophilus colonization. Our results show i/that lactose constitutes a limiting factor for colonization of S. thermophilus, ii/that activation of enzymes involved in carbohydrate metabolism constitutes the metabolic signature of S. thermophilus in the GIT, iii/that the production of lactate settles the dialogue with colon epithelium. We propose a metabolic model of management of carbohydrate resources by S. thermophilus in the GIT. Our results are in accord with the rationale that nutritional allegation via consumption of yogurt alleviates the symptoms of lactose intolerance

How microbes communicate in food: a review of signaling molecules and their impact on food quality

Food ecosystems, and thus food properties, are affected by the development of microorganisms and their ability to interact and communicate. Microbial communication occurs via signaling molecules and is often based on quorum sensing (i.e., stimuli and responses correlated with population density). In bacteria, four groups of signaling molecules have been identified: the autoinducer-2 family, which is found across all bacteria; peptides, which are used by Gram positive bacteria; acyl-homoserine lactones and autoinducer 3, which are used by Gram negative bacteria. In yeasts, the main signaling molecules are alcohols. Microbial communication systems can ultimately influence food quality by affecting both sensory quality (development of beneficial bacteria) and safety (limiting the growth of pathogens and spoilers)

Intérêt des aliments fermentés pour la santé

International audienceFermentation allows to preserve food in a sustainable way at a lower cost and contributes to the world food security. This method of preservation is currently very popular with a population in search of naturalness. Health virtues are also attributed to fermented foods because they contain living micro-organisms or specific macro- and micronutrients. Are these products, or the fermentation process, as such really beneficial to health?La fermentation permet de conserver de manière durable les aliments à moindre coût dans de nombreux pays et participe grandement à la sécurité alimentaire mondiale. Ce mode de conservation est actuellement très prisé par une population en recherche de naturalité. Des vertus santé sont également attribuées aux aliments fermentés parce qu’ils contiennent des microorganismes vivants ou des macro-micronutriments spécifiques. Ces produits, très divers, ou le processus de fermentation en tant que tel sont-ils bénéfiques pour la santé

Les animaux gnotobiotiques : pour mieux comprendre le microbiote intestinal

Gnotobiotic animals to improve our understanding of the intestinal microbiota A large number of data on microbiota has emerged recently, but functional interactions between the microbiota and intestinal cells remain poorly understood, even though they are absolutely essential for health. In this context, we chose two examples of gnotobiotic models used to analyse the dialogue between intestinal cells and microbiota. Animals mono-associated with Bacteroides thetaiotaomicron show the mutual effects between a commensal bacterium and the host. The study of gnotobiotic animals carrying yogurt bacteria helped suggest new pathways for the regulation of sugar metabolism in lactic acid bacteria, and new molecular pathways by which these bacteria may influence the physiology of the host.De nombreuses données récentes concernent le microbiote intestinal, mais les interactions fonctionnelles qui s’établissent entre ce microbiote et les entérocytes restent encore peu connues, alors qu’elles sont tout à fait essentielles pour la santé. Nous avons choisi deux exemples illustrant l’utilisation d’animaux gnotobiotiques pour analyser le dialogue entre les cellules intestinales et le microbiote. Les animaux mono-associés avec la bactérie commensale Bacteroides thetaiotaomicron révèlent les effets mutuels qui existent entre une bactérie commensale et l’hôte. L’étude d’animaux gnotobiotiques, porteurs de bactéries du yaourt, permet de proposer des nouvelles voies de régulation du métabolisme des sucres des bactéries lactiques et de nouvelles voies moléculaires par lesquelles ces bactéries pourraient influencer la physiologie de l’hôte.Thomas Muriel, Wrzosek Laura, Rul Françoise, Langella Philippe. Les animaux gnotobiotiques : pour mieux comprendre le microbiote intestinal. In: Bulletin de l'Académie Vétérinaire de France tome 166 n°1, 2013. pp. 19-23

Postgenomic Analysis of Streptococcus thermophilus Cocultivated in Milk with Lactobacillus delbrueckii subsp. bulgaricus: Involvement of Nitrogen, Purine, and Iron Metabolism▿ †

Streptococcus thermophilus is one of the most widely used lactic acid bacteria in the dairy industry, in particular in yoghurt manufacture, where it is associated with Lactobacillus delbrueckii subsp. bulgaricus. This bacterial association, known as a proto-cooperation, is poorly documented at the molecular and regulatory levels. We thus investigate the kinetics of the transcriptomic and proteomic modifications of S. thermophilus LMG 18311 in response to the presence of L. delbrueckii subsp. bulgaricus ATCC 11842 during growth in milk at two growth stages. Seventy-seven different genes or proteins (4.1% of total coding sequences), implicated mainly in the metabolism of nitrogen (24%), nucleotide base (21%), and iron (20%), varied specifically in coculture. One of the most unpredicted results was a significant decrease of most of the transcripts and enzymes involved in purine biosynthesis. Interestingly, the expression of nearly all genes potentially encoding iron transporters of S. thermophilus decreased, whereas that of iron-chelating dpr as well as that of the fur (perR) regulator genes increased, suggesting a reduction in the intracellular iron concentration, probably in response to H2O2 production by L. bulgaricus. The present study reveals undocumented nutritional exchanges and regulatory relationships between the two yoghurt bacteria, which provide new molecular clues for the understanding of their associative behavior

Aliments fermentés & bénéfices santé : un défi pour la recherche

International audienceFor thousands of years, locally and internationally, a particular family of foods exists in our diet: the fermented foods. These “living” foods, shaped by micro-organisms, have microbiological, biochemical and physicochemical characteristics that are very different from the raw material they are made of. Consequently, they have been granted with many nutritional and health benefits, although the studies that have been conducted on these foods are not sufficient and can hardly be generalised (i.e.: to a generic effect). However, in the current context of expectations of sustainability and naturalness, it is clear that these foods could have a central role to play in our food systems. The issue concerning their health value, especially in the light of new knowledge on the gut microbiota, needs to be clarified in order to consider the place of fermented foods in dietary recommendations.Depuis des millénaires, localement et à l’échelle internationale, existe dans notre diète une famille d’aliments particuliers : les aliments fermentés. Ces aliments « vivants », façonnés par des micro-organismes, ont des caractéristiques microbiologiques, biochimiques et physico-chimiques très différentes de la matière première dont ils sont issus. De ce fait, ils ont été parés de nombreuses vertus nutritionnelles et de santé bien que les études qui ont été réalisées sur ces aliments soient insuffisantes et peinent à esquisser un effet générique. Cependant, dans le contexte actuel des attentes de durabilité et de naturalité, il est clair que ces aliments pourraient avoir un rôle central à jouer dans nos systèmes alimentaires. La question de leur valeur santé, au regard notamment des nouvelles connaissances sur le microbiote intestinal, doit être clarifiée pour pouvoir considérer la place des aliments fermentés dans les recommandations alimentaires