C. Rouquette et al., Induction of the mtrCDE-encoded efflux pump system of Neisseria gonorrhoeae requires MtrA, an AraC-like protein, MOL MICROB, 33(3), 1999, pp. 651-658
The mtr(multiple transferable resistance) gene complex in Neisseria gonorrh
oeae encodes an energy-dependent efflux pump composed of the MtrC-MtrD-MtrE
cell envelope proteins that serves to export structurally diverse antimicr
obial, hydrophobic agents (HAs). Many of these agents have membrane-acting
detergent activity. Using Triton X-100 (TX-100) as a representative HA, we
found that the mtrCDE efflux pump operon could be induced to higher levers
of expression when an HA-sensitive strain was exposed to sublethal concentr
ations of this non-ionic detergent and the structurally related spermicide,
nonoxynol-9. This induction was at the level of mtrCDE gene transcription
and was independent of the MtrR repressor, which normally decreases mtrCDE
gene expression. However, the enhanced resistance of gonococci to TX-100 wa
s dependent on the expression of a previously undescribed gonococcal protei
n that belonged to the AraC/XylS family of transcriptional activators. We h
ave termed this protein MtrA to signify its likely role in the activation o
f mtrCDE gene expression. Taken together with previous studies dealing with
the genetic control of mtrCDE gene expression, we propose that gonococci c
an modulate their resistance to HAs through both positive and negative tran
scriptional control processes. The action of these regulatory processes is
probably of importance in determining the survival capacity of gonococci at
mucosal surfaces that contain detergent-like HAs.