Mapped differences are restricted to size changes of ˜40 intergenic regions, which vary in the two strains because GSK2126458 supplier they contain a different number of short sequence repeats. A major difference can be ascribed to a > 36 kb CP3-like element, found in the 3990 strain only, the chromosomal location of which has not yet been determined. Two CP3-like prophages Vistusertib specific of strains 3909 and 4190 have not yet been mapped as well. The ACICU and 3990 strains are however phenotypically distinguishable, since the his-leu replacement at residue 535 of the beta subunit of the RNA polymerase made the 3990 strain

not susceptible to rifampicin (MIC > 500 mg/L). Sequence comparisons revealed that 3068 coding regions are conserved, at the same chromosomal position, in all A. baumannii genomes. Accessory coding regions, including both GEI- and mhr-encoded ORFs, varies from 433 (3909 strain) to 707 (AB0057 strain). In estimating the number of conserved coding regions, it was taken into account that many correspond to a single ORF in one genome, but to two or even

7-Cl-O-Nec1 three adjacent ORFs in others, and vice versa. Likely most “”double ORFs”" are artifactual, since mutations are known to be introduced by PCR amplification of DNA samples prior to sequencing. Accessory DNA regions correspond to 12% of the 3909 genome, 19% of the AB0057 genome, and to 14-16% of all other genomes analysed. Although closure of draft genomes and addition of whole genome sequences of other strains may lead to the definition of a few additional GEIs, data clearly indicate that A. baumannii strains exhibit less variation than E. coli strains, which may share only 60-70% of their coding capacity [55]. Many A. baumannii GEIs have a role in drug resistance, biosynthesis of surface components, iron metabolism, and this may confer advantage in the course of an infection, Beta adrenergic receptor kinase since successful pathogens encode multiple adhesins, are equipped to sequester iron from the environment and can escape therapy.

Less clear is the advantage conferred to A. baumannii by other islands. The functional role of the RNA 3′-terminal phosphate cyclase, an enzyme conserved among Bacteria, Archaea and Eucarya, encoded by G51ST25 and G51acb, is debated. The same holds for vgr-like proteins, encoded by several GEIs, though it is worth noting that six of the ten genomic islands identified in the pathogenic P. aeruginosa PA01 strain [56] encode vgr-like proteins. Some GEIs carry genes involved in lipid metabolism. G47abn and G47aby carry genes controlling the formation of CFA and UFA phospholipids. Cyclopropanation plays a role in the pathogenesis of Mycobacterium tuberculosis, a specific CFA synthase being required to modify the alpha mycolates on the cell envelope, and pathogenic E. coli strains have higher CFA contents and are more resistant to acid shock than non-pathogenic strains [57].