Sex pheromones and plasmid transfer in Enterococcus faecalis

Abstract

Plasmid-free Enterococcus faecalis excrete peptides (sex pheromones) which specifically induce a mating response in strains harboring certain conjugative plasmids. The response is characterized by the synthesis of a "fuzzy" surface material, visible by electron microscopy, which is believed to facilitate the aggregation of donors and recipients. Transconjugants which receive a specific plasmid shut down the production of endogenous pheromone; however, they continue to produce pheromones specific for donors harboring different classes of plasmids. In this review, we summarize what is known about the biochemistry and genetics of this phenomenon. Some emphasis is given to the hemolysin plasmid pAD1 and the regulation of its conjugal transfer.

Regulation of the pAD1 sex pheromone response in Enterococcus faecalis: effects of host strain and traA, traB, and C region mutants on expression of an E region pheromone-inducible lacZ fusion

“…(pAM2030 contains the A3 deletion [see Fig. 1] and was previously shown to allow cADi production [2,13]). As shown in the table, two of the double-insert plasmids, pAM2045 and to a lesser extent pAM2145, allowed production of cADl in an OGlX background.…”

“…These results were somewhat surprising, since no single E or C region insert or traB single insert which results in cAD1 production has been isolated. The A3 deletion present on pAM2030 disrupts both the C region and traB (2), providing yet another mutant combination resulting in failure to shut down cAD1. The two combinations involving traB (pAM2030 and pAM2045) were least effective in pheromone shutdown.…”

“…The product of the traB gene was believed to function in cooperation with the traA gene product as a negative regulator. In addition, a deletion resulting in the loss of much of the B/C transcript caused the loss of cADI shutdown capability (2). Evaluation of miniplasmids indicated that these genetic determinants were sufficient for negative regulation of the pheromone response, signal transduction, cAD1 shutdown, and iAD1 production, although the specific function of each gene product and their relationships with each other were not identified (14).…”

Role of the pheromone-inducible surface protein Asc10 in mating aggregate formation and conjugal transfer of the Enterococcus faecalis plasmid pCF10

“…Exposure of pure cultures of donor cells to culture filtrates of recipients (12) or to purified peptide pheromones (30,31,33) can induce self-clumping of the donor cells, with kinetics resembling those of the induction of high-frequency transfer ability (30). These observations have been incorporated into a model (6,10,13) which postulates that the pheromone response of donor cells includes the synthesis of a plasmiddetermined surface adhesin, aggregation substance (AS), which mediates attachment to recipient cells via a chromosomally encoded receptor, binding substance (BS). Because donor cells also express BS, they will aggregate with other donor cells, but the subsequent plasmid transfer between aggregated donors appears to be inhibited by a pheromoneinducible surface exclusion mechanism (16).…”

“…Most of this work has focused on three pheromone-inducible plasmids, including the hemolysinbacteriocin plasmid pAD1 (17), the bacteriocin plasmid pPD1 (41), and the tetracycline resistance plasmid pCF10 (14). In the case of the former two plasmids, immunoblotting analysis of cell surface extracts prepared with the detergent Zwittergent (6,20) led to the suggestion that a 78-kDa protein antigen was involved in aggregation. Similar analysis of the pCF10 system, which utilized primarily lysozyme extracts, suggested that a 150-kDa protein (formerly Tral50), now called AsclO, was involved in mating aggregate formation (4,30).…”