The marRAB operon of Escherichia coli is self-repressed by MarR, while the MarA protein activates a number of promoters, including those for the AcrAB/TolC multidrug efflux pump (1, 4, 5). Inactivation of marR leads to a “Mar” multipleantibiotic resistance phenotype. In 1999, the mppA gene was reported to be a novel factor involved in the regulation of the marRAB operon (3). Strain TP985 had be...

Enterococcus gallinarum N04-0414 (MIC for vancomycin, 256 microg/ml) harbored a vanD-type vancomycin resistance operon as well as the intrinsic vanC1 operon. The D-Ala:D-Ala ligase 2 gene (ddl2) was not present in the strain, though it is found downstream of the vanS gene from the vanC operon in E. gallinarum ATCC 49573 and 19 other E. gallinarum strains tested.

We used site-directed mutagenesis to replace the Escherichia coli tryptophanase (tna) operon leader peptide start codon with AUC. This change greatly decreased the uninduced rate of tna operon expression, and it also lowered the response to inducer. We conclude that leader peptide synthesis plays an essential role in tna operon expression.

Enterococcus faecalis G1-0247 (vancomycin MIC, 16 microg/ml) was found to harbor a vanG operon 99% identical to the vanG operon in E. faecalis BM4518. E. faecalis N03-0233 (vancomycin MIC, 16 microg/ml) was found to harbor a novel vanG operon, vanG2, on an element in a different chromosomal location than the vanG-harboring elements in G1-0247 and BM4518.

Biofilm formation in Staphylococcus epidermidis is dependent upon the ica operon-encoded polysaccharide intercellular adhesin, which is subject to phase-variable and environmental regulation. The icaR gene, located adjacent to the ica operon, appears to be a member of the tetR family of transcriptional regulators. In the reference strain RP62A, reversible inactivation of the ica operon by IS256...

We measured the differential transcription rates of individual ribosomal operons after a nutritional shift-up. All operons showed a transient increase in transcription. However, the response of the S10 ribosomal protein operon was much stronger than that of any other operon. We propose that only the S10 operon is autogenously regulated by a transcription attenuation mechanism.