pseudomonads make efflux pumps when treated with tetracycline

[Guest guest]

Here are more findings from recent years. Looks like P. aeruginosa is

up to something similar to Mtb. The presence of tetracyclines causes

wild P. aeruginosa to up-regulate its production of certain multi-

drug efflux pumps by ~13 fold:

http://www.pubmedcentral.gov/articlerender.fcgi?

tool=pubmed & pubmedid=12604529

Similar upregulations by an undetermined, but large fold take place

in response to gentamycin and erythromycon:

http://www.pubmedcentral.gov/articlerender.fcgi?artid=90052

These pumps are barely expressed at all when the bastards are not

looking at antibiotics.

Existence of such a system is more easily understandable in this

organism than in Mtb because it (tho not necessarily the same

strains?) is found in soil where it faces antibiotic producing

microorganisms:

" Pseudomonas aeruginosa was detected in 24% of the soil samples but

in only 0.13% of the vegetable samples from various agricultural

areas of California "

> http://www.pnas.org/cgi/content/abstract/0505446102v1

>

> This looks to be a key factor in Mtb's intrinsic resistance in

glass

> and in flesh to many drugs.

>

> M. tuberculosis and M. smegmatis have a transcription regulator

> which is transcribed 70 fold more in the presence of therapeutic

> concentrations of at least some abx.

>

> Deleting the gene for this regulator brought Mtb MICs of several

> compounds down up to 32-fold. Several of the genes in the regulon

of

> interest were efflux pumps. Their upregulation fold during regulon

> activation was not addressed.

>

> Deleting the orthologous regulator from some soil-dwelling cousins

> of the Mycobacterium genus caused even larger MIC differences, yet

> did not alter sensitivity to 23 non-antibiotic toxins.

>

> Apparantly no nonantibiotic toxins were tested on the Mtb regulator

> mutants (why?). Mtb, unlike many mycobacteria, is not known outside

> the human so it is speculated this equipment may have been

preserved

> from an ancestor present in the soil. Somtheing would have to

> motivate this preservation; perhaps hostile host molecules.

>

> Strangely, although sub- and supra-inhibitory tetracycline both

> induced the regulon in wild type Mtb, mutational disablement of the

> regulon did not alter the tetracycline MIC.