Evolutionary, ecological and biotechnological perspectives on plasmids resident in the human gut mobile metagenome

Numerous mobile genetic elements (MGE) are associated with the human gut microbiota and collectively referred to as the gut mobile metagenome. The role of this flexible gene pool in development and functioning of the gut microbial community remains largely unexplored, yet recent evidence suggests that at least some MGE comprising this fraction of the gut microbiome reflect the co-evolution of host and microbe in the gastro-intestinal tract. In conjunction, the high level of novel gene content typical of MGE coupled with their predicted high diversity, suggests that the mobile metagenome constitutes an immense and largely unexplored gene-space likely to encode many novel activities with potential biotechnological or pharmaceutical value, as well as being important to the development and functioning of the gut microbiota. Of the various types of MGE that comprise the gut mobile metagenome, plasmids are of particular importance since these elements are often capable of autonomous transfer between disparate bacterial species, and are known to encode accessory functions that increase bacterial fitness in a given environment facilitating bacterial adaptation. In this article current knowledge regarding plasmids resident in the human gut mobile metagenome is reviewed, and available strategies to access and characterize this portion of the gut microbiome are described. The relative merits of these methods and their present as well as prospective impact on our understanding of the human gut microbiota is discussed

Chemotaxonomic Features in the Bifidobacteriaceae Family

Chemotaxonomy studies the chemical variation in microbial cells and the use of chemical characteristics in the classification and identification of bacteria; it can be very helpful in the modern approach of bacterial polyphasic taxonomy. For some groups it is one of the most important taxonomic criteria for identification (e.g., Sphingomonas sp.; Busse et al., 1999) while for others, such as Bifidobacteriaceae, it is important but not sufficient for strain identification. It has been recommended in the Bifidobacteriaceae Minimal Standard guidelines for the description of new species (Mattarelli et al., 2014). Chemotaxonomic markers applied in polyphasic approach of Bifidobacteriaceae are here described singularly

Regulation of virulence expression in oral pathogens by lactobacilli

The beneficial impact of dairy foods is indisputable. These foods harbour probiotic microrganisms, as Lactobacilli, which can establish a symbiosis with the host and contribute to its well being. The role of probiotics is mainly to limit indigenous pathogens, and challenge those microbes introduced by altered foods, by well known microbial strategies. In this study we aimed to veritfy the potential of probiotic bacteria to challenge oral pathogens, by attenuation of their virulence

DECREASE IN TOXINS EXPRESSION OF AN ORAL PATHOGEN BY PROBIOTICS

The oral cavity, as the first part of the digestive system, is a reservoir of pathogens for focal infections and the site of origin for dissemination of microbial cells and products. Theoretically, the mechanisms by which oral bacteria may cause non oral diseases in other sites of the GIT are: by translocation of bacteria and their virulence factors, such as toxins, and by immunological imbalance for specific antibodies cross reaction [1]. In fact, oral pathogens, during bacteraemia, can spread their toxins through the bloodstream or through the neighbouring GI sites. Moreover, recent studies have focused on the link between the composition of oral and intestinal microbiota in IBD (Irritable Bowel Disease) patients, and have speculated about a relationship between oral and intestinal diseases. Therefore, to control the colonisation of pathogenic bacteria in the mouth is the first step to limit the dissemination of virulence factors through the GIT

HOST-MICROBIOTA INTERACTIONS: ENVIRONMENTAL STRESS AFFECTING CELL-WALL PROTEIN EXPRESSION IN BIFIDOBACTERIUM SPP.

A potential role of gastrointestinal microbiota in irritable bowel syndrome, obesity, food antigen-related adverse responses and diabetes has been indicated. In many diseases an altered gastrointestinal microbiota is related to the reduction of the population of bifidobacteria. Predicting the distribution and colonization of bifidobacteria in the gastrointestinal tract is increasingly warranted. The interacting strain-inherent and cultivation-dependent effects on microbial cell surface behavior may have broad consequences for the fate and ecology of bifidobacteria, therefore surface properties may determine an isolate's physical fate. In bifidobacteria the effects of environmental factors on the variability of cell-wall protein expression (BIFOP) and gastrointestinal tract adhesion properties have been studied.We have verified in vitro that environmental factors, which can possibly be present in vivo, are able to modify BIFOPs expression and the adhesion potential of bifidobacterial species, suggesting their important role in modulating the co