Different pathways to acquiring resistance genes illustrated by the recent evolution of IncW plasmids.
DNA sequence analysis of five IncW plasmids (R388, pSa, R7K, pIE321, and pIE522) demonstrated that they share a considerable portion of their genomes and allowed us to define the IncW backbone. Among these plasmids, the backbone is stable and seems to have diverged recently, since the overall identity among its members is higher than 95%. The only gene in which significant variation was observed was trwA; the changes in the coding sequence correlated with parallel changes in the corresponding TrwA binding sites at oriT, suggesting a functional connection between both sets of changes. The present IncW plasmid diversity is shaped by the acquisition of antibiotic resistance genes as a consequence of the pressure exerted by antibiotic usage. Sequence comparisons pinpointed the insertion events that differentiated the five plasmids analyzed. Of greatest interest is that a single acquisition of a class I integron platform, into which different gene cassettes were later incorporated, gave rise to plasmids R388, pIE522, and pSa, while plasmids R7K and pIE321 do not contain the integron platform and arose in the antibiotic world because of the insertion of several antibiotic resistance transposons.
Revilla
Carlos
C
Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria-CSIC-IDICAN, C. Herrera Oria s/n, 39011 Santander, Spain.
Garcillán-Barcia
M Pilar
MP
Fernández-López
Raúl
R
Thomson
Nicholas R
NR
Sanders
Mandy
M
Cheung
Martin
M
Thomas
Christopher M
CM
de la Cruz
Fernando
F
D001483:Base Sequence; D003227:Conjugation, Genetic; D004251:DNA Transposable Elements; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004755:Enterobacteriaceae / Q000145:classification / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal; D032023:Integrons / Q000235:genetics; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D010957:Plasmids / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics; D017422:Sequence Analysis, DNA
D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D012097:Repressor Proteins; C119757:TrwA protein, E coli