Transfer of the Δ (argF-lac) U169 mutation between Escherichia coli strains by selection for a closely linked Tn10 insertion

1983 ◽  
Vol 192 (1-2) ◽  
pp. 293-294 ◽  
Author(s):  
Herbert Schweizer ◽  
Winfried Boos
Keyword(s):  
Escherichia Coli ◽  
Tn10 Insertion ◽  
Selection For

scholarly journals Local genic base composition impacts protein production and cellular fitness

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4286 ◽  
Author(s):  
Erik M. Quandt ◽  
Charles C. Traverse ◽  
Howard Ochman
Keyword(s):  
Escherichia Coli ◽  
Base Composition ◽  
Protein Production ◽  
Purifying Selection ◽  
Specific Protein ◽  
Compositional Variation ◽  
Terminal Portion ◽  
A Genome ◽  
Selection For ◽  
Protein Feature

The maintenance of a G + C content that is higher than the mutational input to a genome provides support for the view that selection serves to increase G + C contents in bacteria. Recent experimental evidence fromEscherichia colidemonstrated that selection for increasing G + C content operates at the level of translation, but the precise mechanism by which this occurs is unknown. To determine the substrate of selection, we asked whether selection on G + C content acts across all sites within a gene or is confined to particular genic regions or nucleotide positions. We systematically altered the G + C contents of the GFP gene and assayed its effects on the fitness of strains harboring each variant. Fitness differences were attributable to the base compositional variation in the terminal portion of the gene, suggesting a connection to the folding of a specific protein feature. Variants containing sequence features that are thought to result in rapid translation, such as low G + C content and high levels of codon adaptation, displayed highly reduced growth rates. Taken together, our results show that purifying selection acting against A and T mutations most likely results from their tendency to increase the rate of translation, which can perturb the dynamics of protein folding.

scholarly journals Origin and Evolution of the AmpC β-Lactamases of Citrobacter freundii

2002 ◽  
Vol 46 (5) ◽  
pp. 1190-1198 ◽  
Author(s):  
Miriam Barlow ◽  
Barry G. Hall
Keyword(s):  
Escherichia Coli ◽  
Clinical Isolates ◽  
Citrobacter Freundii ◽  
Clinical Use ◽  
Origin And Evolution ◽  
E Coli ◽  
Selection For

ABSTRACT To determine whether the widespread clinical use of β-lactams has been selective for Citrobacter freundii-derived alleles of plasmid ampC genes, we generated a Bayesian consensus phylogeny of the published ampC sequences and compared the MICs of 16 β-lactam antibiotics for Escherichia coli strains containing cloned copies of the C. freundii ampC alleles. We found that for the majority of compounds investigated, there has been essentially no increase in β-lactam resistance conferred by those alleles. We also found that ampC alleles from the chromosomes of two β-lactam-sensitive C. freundii strains isolated in the 1920s, before the clinical use of antibiotics, were as effective at providing β-lactam resistance in E. coli as were the plasmid-borne alleles from β-lactam-resistant clinical isolates. These results suggest that selection for increased resistance to β-lactam antibiotics has not been a significant force directing the evolution of the C. freundii ampC alleles found in β-lactam-resistant clinical isolates.

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