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DNA Sequencing
(2011)
Isolation of DNA and RNA
(2011)
Polymerase Chain Reaction
(2011)
Streptococcus agalactiae is the leading cause of bacterial sepsis and meningitis in neonates and is also the causative agent of several serious infections in immunocompromised adults. S. agalactiae encounters multiple niches during an infection, suggesting that regulatory mechanisms control the expression of specific virulence factors in this bacterium. The present study describes the functional characterization of a gene from S. agalactiae, designated rga, which encodes a protein with significant similarity to members of the RofA-like protein (RALP) family of transcriptional regulators. After deletion of the rga gene in the genome of S. agalactiae, the mutant strain exhibited significantly reduced expression of the genes srr-1 and pilA, which encode a serine-rich repeat surface glycoprotein and a pilus protein, respectively, and moderately increased expression of the fbsA gene, which encodes a fibrinogen-binding protein. Electrophoretic mobility shift assays demonstrated specific DNA binding of purified Rga to the promoter regions of pilA and fbsA, suggesting that Rga directly controls pilA and fbsA. Adherence assays revealed significantly reduced binding of the Δrga mutant to epithelial HEp-2 cells and to immobilized human keratin 4, respectively. In contrast, the adherence of the Δrga mutant to A549 cells and its binding to human fibrinogen was significantly increased. Immunoblot and immunoelectron microscopy revealed that the quantity of pilus structures was significantly reduced in the Δrga mutant compared with the parental strain. The wild-type phenotype could be restored by plasmid-mediated expression of rga, demonstrating that the mutant phenotypes resulted from a loss of Rga function.
Balanites aegyptiaca (Balanitaceae) is a widely grown desert plant with multiuse potential. In the present paper, a crude extract from B. aegyptiaca seeds equivalent to a ratio of 1 : 2000 seeds to the extract was screened for antiplasmodial activity. The determined IC(50) value for the chloroquine-susceptible Plasmodium falciparum NF54 strain was 68.26 μg/μL ± 3.5. Analysis of the extract by gas chromatography-mass spectrometry detected 6-phenyl-2(H)-1,2,4-triazin-5-one oxime, an inhibitor of the parasitic M18 Aspartyl Aminopeptidase as one of the compounds which is responsible for the in vitro antiplasmodial activity. The crude plant extract had a K(i) of 2.35 μg/μL and showed a dose-dependent response. After depletion of the compound, a significantly lower inhibition was determined with a K(i) of 4.8 μg/μL. Moreover, two phenolic compounds, that is, 2,6-di-tert-butyl-phenol and 2,4-di-tert-butyl-phenol, with determined IC(50) values of 50.29 μM ± 3 and 47.82 μM ± 2.5, respectively, were detected. These compounds may contribute to the in vitro antimalarial activity due to their antioxidative properties. In an in vivo experiment, treatment of BALB/c mice with the aqueous Balanite extract did not lead to eradication of the parasites, although a reduced parasitemia at day 12 p.i. was observed.