RESUMEN
The marine bacterium Photobacterium damselae subsp. damselae (Pdd) causes disease in marine animals and humans. Previous studies demonstrated that mutation of the two-component system RstAB strongly impacts virulence of this pathogen, but the RstAB regulon has not been thoroughly elucidated. We here compared the transcriptomes of Pdd RM-71 and ΔrstA and ΔrstB derivatives using RNA-seq. In accordance with previous studies, RstAB positively regulated cytotoxins Dly, PhlyP and PhlyC. This analysis also demonstrated a positive regulation of outer membrane proteins, resistance against antimicrobials and potential virulence factors by this system. Remarkably, RstAB positively regulated two hitherto uncharacterised gene clusters involved in the synthesis of a polysaccharide capsule. Presence of a capsular layer in wild-type cells was confirmed by transmission electron microscopy, whereas rstA and rstB mutants were non-capsulated. Mutants for capsule synthesis genes, wza and wzc exhibited acapsular phenotypes, were impaired in resistance against the bactericidal action of fish serum and mucus, and were strongly impaired in virulence for fish, indicating a major role of capsule in virulence. Collectively, this study demonstrates that RstAB is a major positive regulator of key virulence factors including a polysaccharide capsule essential for full virulence in a pathogenic Photobacterium.
Asunto(s)
Enfermedades de los Peces , Photobacterium , Animales , Humanos , Photobacterium/genética , Polisacáridos , Virulencia/genéticaRESUMEN
The enantioselective intermolecular gold(I)-catalyzed [2+2] cycloaddition of terminal alkynes and alkenes has been achieved using non-C2-chiral Josiphos digold(I) complexes as catalysts, by the formation of the monocationic complex. This new approach has been applied to the enantioselective total synthesis of rumphellaone A.
Asunto(s)
Ciclobutanos/síntesis química , Oro/química , Sesterterpenos/síntesis química , Catálisis , Reacción de Cicloadición , Ciclobutanos/química , Estructura Molecular , Sesterterpenos/química , EstereoisomerismoRESUMEN
We report the synthesis and biological evaluation of a series of (-)-englerinâ A analogues obtained along our previously reported synthetic route based on a stereoselective gold(I) cycloaddition process. This synthetic route is a convenient platform to access analogues with broad structural diversity and has led us to the discovery of unprecedented and easier-to-synthesize derivatives with an unsaturation in the cyclopentyl ring between C4 and C5. We also introduce novel analogues in which the original isopropyl motif has been substituted with cyclohexyl, phenyl, and cyclopropyl moieties. The high selectivity and growth-inhibitory activity shown by these new derivatives in renal cancer cell lines opens new ways toward the final goal of finding effective drugs for the treatment of renal cell carcinoma (RCC).
Asunto(s)
Antineoplásicos Fitogénicos/síntesis química , Sesquiterpenos de Guayano/química , Antineoplásicos Fitogénicos/química , Antineoplásicos Fitogénicos/farmacología , Catálisis , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Reacción de Cicloadición , Ensayos de Selección de Medicamentos Antitumorales , Oro/química , Humanos , Sesquiterpenos de Guayano/síntesis química , Sesquiterpenos de Guayano/farmacología , Estereoisomerismo , Relación Estructura-ActividadRESUMEN
Silyl ketene acetals are shown to be competent nucleophiles in Pd-catalyzed migrative C(sp(3))-H arylations. Compared to the parent ester lithium enolates, they possess decreased reactivity but enhanced chemoselectivity. This behavior was exploited through the synthesis of valuable benzo-fused δ-lactones such as 1-isochromanones and dihydrocoumarins.