Youjin Yi

The aim of this study was to devise a method to protect Chinese cabbage (Brassica chinensis) and lettuce (Lactuca sativa) from bacterial-disease-induced damage during storage. Thus, the potential of rhapontigenin as a quorum sensing (QS) inhibitor against Pectobacterium carotovorum subsp. carotovorum (P. carotovorum) was evaluated. The QS inhibitory effects of rhapontigenin were confirmed by significant inhibition of the production of violacein in Chromobacterium violaceum CV026 (C. violaceum, CV026). The inhibitory effects of rhapontigenin on the motility, exopolysaccharide (EPS) production, biofilm formation and virulence–exoenzyme synthesis of P. carotovorum were investigated. Acyl-homoserine lactones (AHLs) were quantified using liquid chromatography–mass spectrometry (LC–MS). The inhibitory effects of rhapontigenin on the development of biofilms were observed using fluorescence microscopy and scanning electron microscopy (SEM). A direct-inoculation assay was performed to investigate the QS inhibitory effects of rhapontigenin on P. carotovorum in Chinese cabbage and lettuce. Our results demonstrated that rhapontigenin exhibited significant inhibition (p < 0.05) of the motility, EPS production, biofilm formation, virulence–exoenzyme synthesis and AHL production of P. carotovorum. Additionally, the result of the direct-inoculation assay revealed that rhapontigenin might provide vegetables with significant shelf-life extension and prevent quality loss by controlling the spread of soft-rot symptoms. Consequently, the study provided a significant insight into the potential of rhapontigenin as a QS inhibitor against P. carotovorum.

To study the rudimentary immunoregulatory mechanisms of Ganoderma spore oil on immunocompromized mice model. Thrity KM mice were randomly selected and assigned into three groups (ten animals per group): the model control group, Ganoderma Lucidum spores oil group and the normal control group. The model control group and Ganoderma Lucidum spores oil group were injected intraperitoneally with cyclophosphamide at 40 mg x kg(-1) d to generate a immunocompromized mice model. The normal control group were administered with 0.9% NaCl solution 0.1 ml/10 g BW as placebo. All agents were given orally once a day, given for consecutive 30 days, Ganoderma Lucidum spores oil group 150 mg/kg, the others given maize 0.1 ml/10 g BW. The serum TNF-alpha , IFN-gamma content of the mice through ELISA kit and the expression levels of IL-2, IL-10, IL-12, IL-4, IFN-gamma, TNF-alpha mRNA in mouse spleen and thymus were examined by RT-PCR to rudimentary study its immunoregulatory mechanisms. Ganoderma spore oil can significantly increased the content of TNF-alpha and IFN-gamma in the serum and the expression levels of IL-2, IL-10, IL-12, IL-4, IFN-gamma, TNF-alpha mRNA in spleen and thymus, with obvious difference from the model control (P < or = 0.05). Ganoderma spore oil can be able to improve the above cytokine ion expression to immunoregulate the immunocompromized mice.

In this paper, an endophytic strain B-001 against tobacco bacterial wilt (Ralstonia solanacarum) was isolated from the stem of healthy tobacco in R. solanacarum-infected fields, which had a stronger inhibitory effect on some kinds of gram-positive bacteria, gram-negative bacteria, and pathogenic fungi. This strain belonged to Bacillus, and its 16S rDNA after PCR and sequencing had an accession of GenBank being DQ444283. The 16S rDNA phylogenetic tree was constructed with MEGA3, and compared with the published 16S rDNA sequences of relative bacteria species. B-001 had a 99.2% sequence similarity with Bacillus subtilis (DQ415893). According to the morphological, physiological and biochemical characteristics, and based on phylogenetic analysis, B-001 was identified as a strain of B. subtilis. Field experiments in Guiyang and Ningxiang counties of Hunan Province showed that in 2005 and 2006, the control efficacy of B-001 on R. solanacarum ranged from 40.03% to 78. 14%, better than that of Streptomycini.