Multiple Drug-Resistant Escherichia coli Phylogroups from the Belmont Valley Integrated Algal Pond System

SUMMARYTwo spontaneously formed R-plasmids (pFS401 and pFS402) originating from the multiple drug-resistantEscherichia colistrain UR12644 were found to carry transposable drug-resistance elements. Incompatibility between these two plasmids was used to select for transposition. An ampicillin transposon (Tn1781) residing on pFS401 and a tetracycline transposon (Tn1771) present on pFS402 were independently translocated to the endogenous RTF-plasmid pFS2. Molecular weight determinations of pFS2::Tn1781(Ap) and pFS2::Tn1771(Tc) revealed a value of 2·9 Mdal for Tn1781 and 7·1 Mdal for Tn1771. The arrangement of 3PstI and 1BamHI restriction endonuclease sites was found to be characteristic for the ampicillin transposon whereas the restriction map of Tn1771 features a nearly symmetrical location of 3EcoRI cleavage sites, two of them close to the termini and one in the middle of the transposon. A model is presented suggesting the existence of repetitive DNA-segments at these positions which represent the structural preconditions for the genetic properties of Tn1771. The role of a cryptic plasmid involved in the generation of the endogenous R-plasmids pFS401 and pFS402 is discussed.

Download Full-text

Isolation and Characterization of VceC Gain-of-Function Mutants That Can Function with the AcrAB Multiple-Drug-Resistant Efflux Pump of Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.00038-06 ◽

2006 ◽

Vol 188 (11) ◽

pp. 3757-3762 ◽

Cited By ~ 25

Author(s):

Govindsamy Vediyappan ◽

Tatyana Borisova ◽

Joe A. Fralick

Keyword(s):

Escherichia Coli ◽

Outer Membrane ◽

Efflux Pump ◽

Multiple Drug ◽

Drug Resistant ◽

Membrane Component ◽

Gain Of Function ◽

Isolation And Characterization ◽

Multiple Drug Resistant ◽

Major Facilitator

ABSTRACT VceC is the outer membrane component of the major facilitator (MF) VceAB-VceC multiple-drug-resistant (MDR) efflux pump of Vibrio cholerae. TolC is the outer membrane component of the resistance-nodulation-division AcrAB-TolC efflux pump of Escherichia coli. Although these proteins share little amino acid sequence identity, their crystal structures can be readily superimposed upon one another. In this study, we have asked if TolC and VceC are interchangeable for the functioning of the AcrAB and VceAB pumps. We have found that TolC can replace VceC to form a functional VceAB-TolC MDR pump, but VceC cannot replace TolC to form a functional AcrAB-VceC pump. However, we have been able to isolate gain-of-function (gof) VceC mutants which can functionally interface with AcrAB. These mutations map to four different amino acids located at the periplasmic tip of VceC. Chemical cross-linkage experiments indicate that both wild-type and gof mutant VceC can physically interact with the AcrAB complex, suggesting that these gof mutations are not affecting the recruitment of VceC to the AcrAB complex but rather its ability to functionally interface with the AcrAB pump.

Download Full-text