ABSTRACT
The rise of drug-resistant fungal pathogens urges for the development of new tools for the discovery of novel antifungal compounds. Polyene antibiotics are potent agents against fungal infections in humans and animals. They inhibit the growth of fungal cells by binding to sterols in the cytoplasmic membrane that subsequently causes pore formation and eventually results in cell death. Many polyenes are produced by Streptomycetes and released into the soil environment, where they can then target fungal hyphae. While not antibacterial, these compounds could nevertheless be also perceived by bacteria sharing the same habitat and serve as signaling molecules. We therefore addressed the question of how polyenes such as amphotericin B are perceived by the soil bacterium, Bacillus subtilis. Global transcriptional profiling identified a very narrow and specific response, primarily resulting in strong upregulation of the lnrLMN operon, encoding an ABC transporter previously associated with linearmycin resistance. Its strong and specific induction prompted a detailed analysis of the lnrL promoter element and its regulation. We demonstrate that the amphotericin response strictly depends on the two-component system LnrJK and that the target of LnrK-dependent gene regulation, the lnrLMN operon, negatively affects LnrJK-dependent signal transduction. Based on this knowledge, we developed a novel whole-cell biosensor, based on a P lnrL -lux fusion reporter construct in a lnrLMN deletion mutant background. This highly sensitive and dynamic biosensor is ready to be applied for the discovery or characterization of novel amphotericin-like polyenes, hopefully helping to increase the repertoire of antimycotic and antiparasitic polyenes available to treat human and animal infections.
ABSTRACT
Resumen: Los primeros compuestos con actividad antifúngica específica fueron identificados a mediados del siglo pasado como un producto del metabolismo secundario de bacterias del orden Actinomycetales, y su uso en la clínica redujo de manera importante la morbilidad y la mortalidad relacionadas con infecciones severas por hongos de varios géneros. Muchos de estos compuestos biosintéticos se caracterizan por tener una estructura química de tipo poliénico, con un número variable de dobles enlaces carbono-carbono. Actualmente, además de los fármacos poliénicos, existe otro tipo de compuestos con actividad antimicótica, como los azoles, que se utilizan con mayor frecuencia y que presentan menor toxicidad en los pacientes; sin embargo, se han documentado casos de falla terapéutica con tales compuestos, por lo que el uso de los poliénicos se ha mantenido como la mejor alternativa en esos casos. El presente trabajo brinda información acerca de las propiedades y las aplicaciones de los antifúngicos poliénicos teniendo como modelo a la anfotericina B.
Abstract The first compounds with specific antifungal activity were identified in the middle of the last century as a product of the secondary metabolism of bacteria of the order Actinomycetales, and their clinical use significantly diminished the morbidity and mortality associated with severe fungal infections. Many of such biosynthetic compounds are characterized by a chemical polygenic structure, with a variable number of carbon-carbon double bonds. Currently, besides polygenic antimycotics, there are other antifungal agents, such as the azole compounds, that have less toxicity in patients; however, cases of therapeutic failure with such compounds have been documented, therefore, the use of polygenics is still the best alternative in such cases. This review presents data about the properties and applications of antifungal-polygenic compounds using amphotericin B as a model.
