Molecular gentic analysis of pheromone-independent highly transferable plasmid of Enterococci

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1. Enterocuccus faecium drug resistance plasmid pMG1 (Gm^r, Km^r) was chosen to study the regulation of tra genes in conjugation. To reveal the presence of the regularotry system of tra genes, we searched the plasmid gene, of which transcription was regulated during conjugation. One transcript of the gene named 71ORF2 was found to increase in 20 min mating.2. By gene disruption experiment, 71 ORF2 gene was found to be responsible for the formation or stabilization of mating aggregates.3. 71ORF2 gene was expressed constitutively in some tra mutants, implying that 71ORF2 gene is negatively regulated.4. In tra13101 mutant strain 710RF2 gene was expressed constitutively.tra 13101 mutation was mapped and DNA sequence around it was determined.75ORF4 gene was found to regulate the expression of 71ORF2 gene.5. Transcript of 75ORF4 gene was found to decrease in response to conjugation, while that of 71ORF2 gene incresed.6. From the patterns of 75ORF4 gene expression in tra mutant strains, 75ORF4 gene seems to be regulated by more than one way.