Related Experiment Videos
Polymorphism in the aerobactin-cloacin DF13 receptor genes from an enteroinvasive strain of Escherichia coli and
C L Marolda1, M A Valvano, J H Crosa
1Department of Microbiology and Immunology, Oregon Health Sciences University, Portland 97201.
Abstract:
We have cloned chromosomal genes mediating the aerobactin iron transport system from the enteroinvasive strain Escherichia coli 978-77. The physical map of the region spanning the siderophore biosynthesis genes and the upstream portion of the receptor gene in strain 978-77-derived clones was identical to the corresponding regions in pColV-K30, while the downstream portion was different. Recombinant plasmids derived from strain 978-77 encoded a 76-kDa outer membrane protein, in contrast to the 74-kDa polypeptide encoded by similar clones derived from pColV-K30. No differences were found in the uptake of ferric aerobactin mediated by either the 76-kDa- or the 74-kDa-encoding plasmids. In contrast, cells containing the 76-kDa-encoding plasmids showed a 16-fold decrease in susceptibility to cloacin compared with cells harboring the 74-kDa-encoding plasmids. Two classes of chimeric aerobactin receptor genes were constructed by exchanging sequences corresponding to the downstream portion from the aerobactin receptor gene of both systems. The pColV-K30-978-77 chimeric gene encoded a 76-kDa outer membrane protein which mediated a low level of cloacin susceptibility, whereas the 978-77-pColV-K30 type encoded a protein of 74 kDa determining a level of cloacin susceptibility identical to that mediated by pColV-K30.
Insights
Researchers cloned aerobactin iron transport genes from Escherichia coli 978-77. Differences in the receptor gene
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The aerobactin iron transport system is crucial for bacterial virulence.
- Understanding genetic variations in this system can reveal mechanisms of antimicrobial resistance.
Purpose of the Study:
- To clone and characterize the aerobactin iron transport genes from an enteroinvasive Escherichia coli strain.
- To investigate the functional differences between aerobactin receptor proteins from different E. coli strains.
Main Methods:
- Gene cloning and physical mapping of the aerobactin system region.
- Construction of recombinant plasmids and expression of outer membrane proteins.
- Analysis of ferric aerobactin uptake and susceptibility to cloacin.
Main Results:
- Cloned genes from E. coli 978-77 showed structural differences in the receptor gene's downstream region compared to pColV-K30.
- Recombinant plasmids encoded distinct outer membrane proteins (76-kDa vs. 74-kDa).
- The 76-kDa protein conferred significantly reduced susceptibility to cloacin.
Conclusions:
- Structural variations in the aerobactin receptor gene influence outer membrane protein function.
- These variations impact bacterial susceptibility to specific antimicrobial agents like cloacin.
- Chimeric receptor genes demonstrate that specific gene regions determine protein size and cloacin resistance.