Pan-genomics: Unmasking the gene diversity hidden in the bacteria species.

The dramatic increase in genome sequencing during the last years has changed our ideas about bacteria diversity, from single gene to whole community DNA surveys; we have learned that the nature largest gene repository resides in bacteria. Comparison of bacteria genomes has contributed to understand the flexibility in size and gene content as well as the gene movement due to gene family expansions and Horizontal Gene Transfer. Bacteria species are currently defined by means of 16S rRNA sequence comparisons and some limited phenotypic traits. There is an ongoing debate about the biological and evolutive significance of the bacteria species, and thus the need of refine the definition of it using the most of the genomic shared information. When comparing multiple genomes of related strains we can divide the common shared features like the core genome, and the strain specific genes are known as accessory genome, both accessory and core genome as the total of the genetic composition are known as pan-genome. Here we present the possibilities using pan-genomics as a workhorse to describe both taxonomical and functional diversity within bacteria.