Core and variable components in prokaryotic genomes

Abstract

Acinetobacter baumannii and Stenotrophomonas maltophilia are opportunistic pathogens responsable for several hospital-acquired infections. We performed Extensive comparative analyses were performed in silico to elucidate the cromosomal organization of both species, and identify core and variable genome component in each. In the case of S. maltophilia, the genomes of strains isolated from the blood of a cancer patient (K279a strain) and the poplar Populus trichocarpa (R551-3 strain) have been compared. The analyzed chromosomes exhibit extensive synteny and 3620 homologous genes are located at the same relative position in the two strains. However, the R551-3 and the K279a chromosomes vary significantly, as they contain 13% and 19% of specific DNAs sequences, respectively. This DNA fraction is largely represented by unrelated foreign DNA segments or genomic islands (GEIs), which vary in size from 3 to 70 kb. Similar work was done by comparing of the genomes of seven clinical isolates of A. baumannii. The analyzed DNAs also showed extensive synteny. We have identified 3068 conserved coding regions in all isolates, and 63 variable genomic loci containing GEIs ranging in size from 4 o 126 kb. GEIs found in A. baumannii and S. maltophilia GEIs are, except for some resistance islands, unrelated.