BACKGROUND: Pantoea ananatis is found in a wide range of natural environments, including water, soil, as part of
the epi- and endophytic flora of various plant hosts, and in the insect gut. Some strains have proven effective as
biological control agents and plant-growth promoters, while other strains have been implicated in diseases of a
broad range of plant hosts and humans. By analysing the pan-genome of eight sequenced P. ananatis strains isolated
from different sources we identified factors potentially underlying its ability to colonize and interact with hosts in both
the plant and animal Kingdoms.
RESULTS: The pan-genome of the eight compared P. ananatis strains consisted of a core genome comprised of 3,876
protein coding sequences (CDSs) and a sizeable accessory genome consisting of 1,690 CDSs. We estimate that ~106
unique CDSs would be added to the pan-genome with each additional P. ananatis genome sequenced in the
future. The accessory fraction is derived mainly from integrated prophages and codes mostly for proteins of unknown
function. Comparison of the translated CDSs on the P. ananatis pan-genome with the proteins encoded on all
sequenced bacterial genomes currently available revealed that P. ananatis carries a number of CDSs with orthologs
restricted to bacteria associated with distinct hosts, namely plant-, animal- and insect-associated bacteria. These CDSs
encode proteins with putative roles in transport and metabolism of carbohydrate and amino acid substrates,
adherence to host tissues, protection against plant and animal defense mechanisms and the biosynthesis of potential
pathogenicity determinants including insecticidal peptides, phytotoxins and type VI secretion system effectors.
CONCLUSIONS: P. ananatis has an ‘open’ pan-genome typical of bacterial species that colonize several different
environments. The pan-genome incorporates a large number of genes encoding proteins that may enable P. ananatis
to colonize, persist in and potentially cause disease symptoms in a wide range of plant and animal hosts.