RESUMO
In this study, a deletion mutant of rfaB (DeltarfaB) was observed to be susceptible to sodium dodecyl sulfate and less tolerant to bile salts. In addition, pre-incubation in 10% bile salts increased bacterial tolerance to 30% bile salts. We also showed that the DeltarfaB mutant invaded HeLa cells less than the wild type and resulted in a lower ratio of intracellular bacteria. Competitive infection of mice showed that the DeltarfaB mutant was defective in the colonization of host organs and was cleared more quickly in fecal shedding. Transforming of a plasmid containing a wild-type allele of rfaB (pRB3-rfaB) partially rescued the defect of the DeltarfaB mutant. The results suggest that RfaB, which is responsible to add the glycosyl residue to the core lipopolysaccharide, contributes to the tolerance to detergent and the virulence of Salmonella enterica serovar Enteritidis.
Assuntos
Proteínas de Bactérias/metabolismo , Detergentes/farmacologia , Galactosiltransferases/metabolismo , Salmonella enteritidis/enzimologia , Animais , Proteínas de Bactérias/genética , Galactosiltransferases/genética , Teste de Complementação Genética , Células HeLa , Humanos , Lipopolissacarídeos , Camundongos , Salmonella enteritidis/genética , Salmonella enteritidis/crescimento & desenvolvimento , Salmonella enteritidis/patogenicidade , Deleção de Sequência , VirulênciaRESUMO
Endogenously occurring nitric oxide (NO) is involved in the regulation of shikonin formation in Onosma paniculatum cells. NO generated after cells were inoculated into shikonin production medium reached the highest level after 2 d of culture, which was 16 times that at the beginning of the experiment, and maintained a high level for 6 d. A nitric oxide synthase (NOS) inhibitor, N(omega)-nitro-L-arginine (L-NNA), and a nitrate reductase (NR) inhibitor, sodium azide (SoA), consistent with their inhibition of NO biosynthesis, decreased shikonin formation significantly. This reduction could be alleviated or even abolished by exogenous NO supplied by sodium nitroprusside (SNP), suggesting that the inhibition of NO biosynthesis resulted in decreased shikonin formation. However, when endogenous NO biosynthesis was up-regulated by the elicitor from Rhizoctonia cerealis, shikonin production was enhanced further, showing a dependence on the elicitor-induced NO burst. Real-time PCR analysis showed that NO could significantly up-regulate the expression of PAL, PGT and HMGR, which encode key enzymes involved in shikonin biosynthesis. These results demonstrated that NO plays a critical role in shikonin formation in O. paniculatum cells.
