Dye Sensitivity Correlated with Envelope Protein Changes in dye (sfrA) Mutants of Escherichia coli K12 Defective in the Expression of the Sex Factor F

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Abstract
Mutations of the dye gene on the E. coli chromosome result in sensitivity to toluidine blue and, in male cells, cause loss of F pili, producing sterility in conjugation. Compared with its dye+ parent, a strain deleted for dye (.DELTA.dye) showed an altered sensitivity to a wide range of dyes and antibiotics which affect different intracellular processes; hence, it appeared that the barrier properties of the cell envelope were impaired. Unlike mutants defective in lipopolysaccharide (LPS) structure, there appeared to be no correlation between the hydrophobicity of the compounds and the sensitivity of the .DELTA.dye strain. There was also no difference between dye+ and .DELTA.dye strains in their sensitivity to LPS-specific phages, and chemical and GLC analysis of LPS components revealed no difference between the 2 strains. Examination of outer and inner membrane proteins from isogenic strains having the .DELTA.dye deletion and the dye+ gene cloned into the plasmid pACYC184, with or without insertional inactivation of dye by the transposon .gamma..delta., was performed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This revealed several differences in the profile of inner and outer membrane proteins, correlated with mutation in the dye gene. The dye gene appears to be identical to the sfrA gene, which is required for efficient transcription of the sex fator F. The dye (sfrA) gene product may also control the expression of chromosomal genes coding for envelope proteins.

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