SRA

Background: The bond with our microbiota starts at birth and has co-evolved where fitness of the two participants has become interdependent. Recent comprehensive analysis of the infant microbiota indicates that the family Bifidobacteriaceae is dominant (~80%), compared with approx. 10% for the phylum Firmicutes. Importantly, high levels of bifidobacteria in the infant gut have been associated with the timely development and maturation of mucosal immunity and reduced infection rates. Members of this genus have been used in a wide variety of studies to promote health and as probiotics, however the mechanisms behind these events are as yet not fully characterised. Bifidobacteria are Gram-positive, anaerobic, non-spore forming, non-motile, non-filamentous rods with high G+C content belonging to the phylum Actinobacteria. Indeed, Bifidobacterium represents one of the largest genus within the Actinobacteria, and includes at present 51 species. In the context of early life, bifidobacteria are also found within breast milk, and these strains have enzymes capable of metabolising milk oligosaccharides, enabling growth and persistence, suggesting co-evolution of bacteria-host and diet. Bifidobacteria have also been extensively detected in the gut of mammals, birds and social insects. Due to their associated health benefits, there is significant need to explore the diversity of the bifidobacterial population at a global level and within individuals. Although the genetic diversity of Bifidobacterium has been determined based on several marker genes or a relatively small number of genomes, the global diversity and evolution scenario for the entire genus remain unresolved.