C-30 promotes swarming of nalD mutant
Finally after some long delay we started the project, incorporating a short stay undergraduate Peruvian student from Buffalo University miss Carolina Millan Leon.
So far we have the following strains:
Strain |
Characteristic |
PA14 wild-type |
|
PA14 mexR |
Transposon mutant with a disrupted repressor of the efflux pump MexAB-OprM |
PA14 nalD |
Transposon mutant with a disrupted repressor of the efflux pump MexAB-OprM |
PA14 mexA |
Transposon mutant with a disrupted structural gene of the efflux pump MexAB-OprM |
INP 49R |
Clinical isolate from Cystic Fibrosis patient with dysfunctional mexA and mexE genes |
First swarming motility of each strain was evaluated; however pre-cultures of mexR had notorious lysis so this strain may have something wrong hence we will try to obtain another copy.
Next we evaluated the effect of the QS inhibitor C-30 which is efflux by MexAB-OprM which also efflux the QS signal 3-Oxo-C12-HSL and several antibiotics.
As expected C-30 at 50 uM inhibited swarming of the PA14 wt strain and of the mexA strain (that lacks a functional MexAB-OprM pump) at 12.5-25 uM, in contrast at 25 uM it promoted the swarming of nalD!
Our explanation is that the nalD strain which over express the pump efflux the signal so the intracellular concentration is low and then QS controlled phenotypes like swarming are low, however adding C-30 will keep the pump busy, hence the QS signal will accumulate and QS dependent phenotypes will increase.
Now we are testing swarming of the other strains in the presence and absence of C-30, and antibiotics like ceftazidime and carbenicillin which are efflux by MexAB-OprM, and also growth curves and we will begin to measure other QS controlled phenotypes such as pyocyanin and exoproteases.
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