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Journal of Bacteriology, January 2006, p. 599-608, Vol. 188, No. 2
0021-9193/06/$08.00+0     doi:10.1128/JB.188.2.599-608.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

The ß-Oxidation Systems of Escherichia coli and Salmonella enterica Are Not Functionally Equivalent

Surtaj Hussain Iram1 and John E. Cronan1,2*

Departments of Biochemistry,1 Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 618012

Received 26 August 2005/ Accepted 24 October 2005

Based on its genome sequence, the pathway of ß-oxidative fatty acid degradation in Salmonella enterica serovar Typhimurium LT2 has been thought to be identical to the well-characterized Escherichia coli K-12 system. We report that wild-type strains of S. enterica grow on decanoic acid, whereas wild-type E. coli strains cannot. Mutant strains (carrying fadR) of both organisms in which the genes of fatty acid degradation (fad) are expressed constitutively are readily isolated. The S. enterica fadR strains grow more rapidly than the wild-type strains on decanoic acid and also grow well on octanoic and hexanoic acids (which do not support growth of wild-type strains). By contrast, E. coli fadR strains grow well on decanoic acid but grow only exceedingly slowly on octanoic acid and fail to grow at all on hexanoic acid. The two wild-type organisms also differed in the ability to grow on oleic acid when FadR was overexpressed. Under these superrepression conditions, E. coli failed to grow, whereas S. enterica grew well. Exchange of the wild-type fadR genes between the two organisms showed this to be a property of S. enterica rather than of the FadR proteins per se. This difference in growth was attributed to S. enterica having higher cytosolic levels of the inducing ligands, long-chain acyl coenzyme As (acyl-CoAs). The most striking results were the differences in the compositions of CoA metabolites of strains grown with octanoic acid or oleic acid. S. enterica cleanly converted all of the acid to acetyl-CoA, whereas E. coli accumulated high levels of intermediate-chain-length products. Exchange of homologous genes between the two organisms showed that the S. enterica FadE and FadBA enzymes were responsible for the greater efficiency of ß-oxidation relative to that of E. coli.

* Corresponding author. Mailing address: Department of Microbiology, University of Illinois, B103 Chemical and Life Sciences Laboratory, 601 S. Goodwin Ave., Urbana, IL 61801. Phone: (217) 333-7919. Fax: (217) 244-6697. E-mail: j-cronan{at}life.uiuc.edu.

Journal of Bacteriology, January 2006, p. 599-608, Vol. 188, No. 2
0021-9193/06/$08.00+0     doi:10.1128/JB.188.2.599-608.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Feng, Y., Cronan, J. E. (2009). A New Member of the Escherichia coli fad Regulon: Transcriptional Regulation of fadM (ybaW). J. Bacteriol. 191: 6320-6328 [Abstract] [Full Text]  
  • Shen, Y.-Q., Lang, B. F., Burger, G. (2009). Diversity and dispersal of a ubiquitous protein family: acyl-CoA dehydrogenases. Nucleic Acids Res 37: 5619-5631 [Abstract] [Full Text]  
  • Brown, R. N., Gulig, P. A. (2008). Regulation of Fatty Acid Metabolism by FadR Is Essential for Vibrio vulnificus To Cause Infection of Mice. J. Bacteriol. 190: 7633-7644 [Abstract] [Full Text]  


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