Sex pheromone plasmid pAD1‐encoded aggregation substance of Enterococcus faecalis is positively regulated in trans by traE1

Abstract

Sex‐pheromone‐plasmid‐bearing strains of Enterococcus faecalis react with sex pheromone to induce the expression of an adhesin, the so‐called aggregation substance, on their cell surface. Here we show that, by complementation studies, for sex‐pheromone plasmid pAD1, expression of the structural gene asa1, coding for an aggregation substance, is mediated by a diffusible factor encoded on pAD1. We were able to demonstrate that a small open reading frame, traE1, is sufficient for transcription of the operon containing asa1. A model for expression of asa1 under the influence of the positive regulator is presented, which is supported by our observation that regulation involves an all‐or‐nothing induction phenomenon, leading to cells either fully expressing asa1 or not at all. Copyright © 1993, Wiley Blackwell. All rights reserved