Final Activity Report Summary - BIF-GENOMICS (Genome sequencing of the pathogenic bifidobacterial strain Bifidobacterium dentium: insights from genetics and comparative genomics)
Bifidobacteria represent an ideal target for studying the genetic borderline between health-promoting bacteria (probiotic) and pathogenic bacteria since they include both species with food-grade and probiotic properties as well as species exhibiting typical pathogenic characteristics. This latter group of bifidobacterial strains includes Bifidobacterium dentium species which has a DNA-DNA relatedness above 60 % with the probiotic B. longum species, and which was firstly isolated from dental caries in human abscesses. Since bacterial genomics together with comparative genomics has been considered a valid mean to understand the interactive genetics underlying all microbial properties, we have decoded the genome of B. dentium strain Bd1 and through a comparative genomics approach with other genome sequences from bifidobacterial strains which depict probiotic properties we have identified DNA regions that may sustain 'probiotic functions'.
The genome sequence of B. dentium is in size 2.6 Mb, and display architectural features of a typical bacterial chromosome. Genome analyses of B. dentium Bd1 revealed genetic features that may play a crucial role in the establishment of B. dentium Bd1 cells within the host, i.e. exopolysaccharide or genes involved in sugar metabolism.
The availability of the whole genome sequences from B. dentium Bd1 allowed the identification of prophage sequences that resembled to those already described in B. longum biotype longum NCC2705, B. longum biotype longum DJO1A and B. breve UCC2003. Furthermore, phylogenetic investigations based on B. dentium prophages established genetic connections not only with the lambdoid phages of high-G+C bacteria such as Mycobacterium, Streptomyces, and Corynebacterium species, but also with phages of low-G+C bacteria (e.g. Lactococcus), which may suggest a common ancestry among double-stranded DNA bacteriophages.
Furthermore, the sequencing of B. dentium Bd1 strain revealed the presence of a large number of genetic traits that may sustain an ecological adaptation of this strain to the human mouth niche and thus providing a cariogenic phenotype to this strain. These involve adhesion factors, proteases and surface proteins.
Finally, comparative genomics as well as bioinformatics analyses revealed that B. dentium strain Bd1 possesses a highly level conservation with respect to synteny and gene content to the genome of B. adolescentis ATCC 15703. Such analyses revealed also DNA regions that resulted to be uniquely present in the genome of B. dentium Bd1 strain.
The genome sequence of B. dentium is in size 2.6 Mb, and display architectural features of a typical bacterial chromosome. Genome analyses of B. dentium Bd1 revealed genetic features that may play a crucial role in the establishment of B. dentium Bd1 cells within the host, i.e. exopolysaccharide or genes involved in sugar metabolism.
The availability of the whole genome sequences from B. dentium Bd1 allowed the identification of prophage sequences that resembled to those already described in B. longum biotype longum NCC2705, B. longum biotype longum DJO1A and B. breve UCC2003. Furthermore, phylogenetic investigations based on B. dentium prophages established genetic connections not only with the lambdoid phages of high-G+C bacteria such as Mycobacterium, Streptomyces, and Corynebacterium species, but also with phages of low-G+C bacteria (e.g. Lactococcus), which may suggest a common ancestry among double-stranded DNA bacteriophages.
Furthermore, the sequencing of B. dentium Bd1 strain revealed the presence of a large number of genetic traits that may sustain an ecological adaptation of this strain to the human mouth niche and thus providing a cariogenic phenotype to this strain. These involve adhesion factors, proteases and surface proteins.
Finally, comparative genomics as well as bioinformatics analyses revealed that B. dentium strain Bd1 possesses a highly level conservation with respect to synteny and gene content to the genome of B. adolescentis ATCC 15703. Such analyses revealed also DNA regions that resulted to be uniquely present in the genome of B. dentium Bd1 strain.