Molecular and General Genetics MGG

, Volume 228, Issue 3, pp 410–416

Isolation and genetic analysis of a mutation that suppresses the auxotrophies of superoxide dismutase-deficient Escherichia coli K12

  • James A. Imlay
  • Irwin Fridovich

DOI: 10.1007/BF00260634

Cite this article as:
Imlay, J.A. & Fridovich, I. Molec. Gen. Genet. (1991) 228: 410. doi:10.1007/BF00260634


The most striking phenotype associated with superoxide dismutase (SOD) deficiency in Escherichia coli is the inability to grow in aerobic minimal medium, which is due to the sensitivity of several amino acid biosynthetic pathways to superoxide. We have isolated two classes of pseudorevertants that grow on minimal medium at modest rates. Of these, the class that exhibited the faster growth carries mutations at a single locus, denoted ssa, which was mapped to 4 min on the E. coli chromosome. This class constituted the majority of the spontaneous pseudorevertants that were selected by the transfer of independent SOD-deficient cultures in minimal medium from anaerobic to aerobic growth conditions. Pseudoreversion at ssa suppressed requirements for a variety of unrelated amino acid supplements. Further, the SOD-deficient strains were unable to assimilate diaminopimelic acid from the growth medium, whereas the ssa pseudorevertants did so. The viability of these pseudorevertants indicates that superoxide-sensitive biosynthetic enzymes do retain some function in SOD-deficient cells during aerobic growth.

Key words

Superoxide Superoxide dismutase Oxidative damage Membrane damage Aerotolerance 

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • James A. Imlay
    • 1
  • Irwin Fridovich
    • 1
  1. 1.Department of BiochemistryDuke University Medical CenterDurhamUSA

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