RESUMEN
Serratia marcescens 2170 produces three different types of chitinases and chitin-binding protein CBP21. We found that transposon insertion into the 5' untranslated region (5' UTR) of chiPQ-ctb led to defective chitinase and CBP21 production. ChiX small RNA possessed the complementary sequence of the 5' UTRs of the chiPQ-ctb and chiR and repressed the expression of chiP and chiR. ChiX was detected in a medium containing glucose, glycerol, GlcNAc, and (GlcNAc)2, but the expression of both chiP and chiR was only observed in a medium containing (GlcNAc)2. ∆chiX mutant produced chitinases, CBP21, and chitobiase without induction. chiP transcripts were more abundant than those of chiR or chiX in a medium containing (GlcNAc)2. These results suggest that the constitutively expressed ChiX binds to the highly abundant chiP 5' UTR, thereby leading to the induction of chiR mRNA translation and the subsequent expression of chitinases and CBP21.
Asunto(s)
Proteínas Bacterianas/genética , Quitina/metabolismo , Quitinasas/genética , Regulación Bacteriana de la Expresión Génica , ARN Pequeño no Traducido/genética , Serratia marcescens/genética , Regiones no Traducidas 5' , Acetilglucosamina/metabolismo , Acetilglucosaminidasa/genética , Acetilglucosaminidasa/metabolismo , Proteínas Bacterianas/metabolismo , Secuencia de Bases , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Quitinasas/metabolismo , Glucosa/metabolismo , Glicerol/metabolismo , Hidrólisis , Péptidos y Proteínas de Señalización Intracelular , Isoenzimas/genética , Isoenzimas/metabolismo , Datos de Secuencia Molecular , Biosíntesis de Proteínas , ARN Pequeño no Traducido/metabolismo , Serratia marcescens/metabolismoRESUMEN
In order to elucidate the roles of ChiP, ChiQ, and ChiX in chitin utilization by Serratia marcescens 2170, the construction of single-gene deletion mutants of the chiP, chiQ, and chiX genes was attempted by allelic exchange mutagenesis. ΔchiP formed smaller clearing zones and ΔchiX formed larger ones than wild-type 2170 on an agar plate containing colloidal chitin. ΔchiP grew slowly on the lower concentration of (GlcNAc)2, and there was essentially no growth on chitin oligosaccharides larger than (GlcNAc)3. The gene product of chiP was detected in the outer membrane fraction, consistently with the hypothesis that chiP encodes outer membrane chitoporin. Deletion of chiQ decreased and that of chiX increased the growth rates on chitin oligosaccharides. These observations strongly suggest that all three genes are involved in chitin utilization and that the deletion mutants obtained in this study might prove useful tools to clarify the details of the chitin utilization system of this bacterium.