Journal of Microbiology

Research Support, Non-U.S. Gov't

Interaction of Acinetobacter baumannii 19606 and 1656-2 with Acanthamoeba castellanii: Migma Dorji Tamang , Shukho Kim , Sung-Min Kim , Hyun-Hee Kong , Jungmin Kim; J. Microbiol. 2011;49(5):841-846. Published online November 9, 2011; DOI: https://doi.org/10.1007/s12275-011-1063-8

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Abstract: Acinetobacter baumannii is virtually avirulent for healthy people but maintains a high virulence among critically ill patients or immuno-compromised individuals. The ability of A. baumannii to adhere to cells and persist on surfaces as biofilms could be central to its pathogenicity. In the present study, we compared the virulence of the A. baumannii 1656-2 clinical strain, which is able to form a thick biofilm, with the virulence of the A. baumannii type strain (ATCC 19606T). Acanthamoeba castellanii, a single-celled organism, was used as the host model system to study the virulence of A. baumannii. Compared to A. baumannii ATCC 19606T, A. baumannii 1656-2 exhibited a higher ability to adhere and invade A. castellanii cells and had a higher killing rate of A. castellanii cells. Furthermore, co-incubation of the amoeba cells and the cell-free supernatant of A. baumannii resulted in the cell death of the amoebae. Heat inactivation or proteinase K treatment of the supernatant did not eliminate its cytotoxicity, suggesting heat stable non-protein factors are responsible for its cytotoxicity to A. castellanii cells. In conclusion, this study for the first time has revealed the capacity of the A. baumannii strain and/or its metabolic products to induce cytotoxicity in A. castellanii cells.

Journal Article

Purification and Characterization of a New L-Methioninase from Solid Cultures of Aspergillus flavipes: Ashraf S. A. El-Sayed; J. Microbiol. 2011;49(1):130-140. Published online March 3, 2011; DOI: https://doi.org/10.1007/s12275-011-0259-2

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Abstract: L-Methioninase was purified to electrophoretic homogeneity from cultures of Aspergillus flavipes using anionexchange and gel filtration chromatography by 12.1 fold compared to the crude enzyme preparation. The purified enzyme had a molecular mass of 47 kDa under denaturing conditions and an isoelectric point of 5.8 with no structural glycosyl residues. The enzyme had optimum activity at pH 7.8 and pH stability from 6.8-8.0 at 35°C. The enzyme appeared to be catalytically stable below 40°C. The enzyme activity was strongly inhibited by DL-propargylglycine, hydroxylamine, PMSF, 2-mercaptoethanol, Hg2+, Cu2+, and Fe2+, with slight inhibition by Triton X-100. A. flavipes L-methioninase has a higher catalytic affinity towards L-methionine (Km, 6.5 mM and Kcat, 14.1 S-1) followed by a relative demethiolating activity to L-homocysteine (Km, 12 mM and Kcat, 9.3 S-1). The enzyme has two absorption maxima at 280 and 420 nm, typical of other PLP-enzymes. Apo-L-methioninase has the ability to reconstitute its structural catalytic state completely upon addition of 0.15 mM PLP. L-Methioninase has neither an appreciable effect on liver function, platelet aggregation, nor hemolysis of human blood. The purified L-methioninase from solid cultures of A. flavipes displayed unique biochemical and catalytic properties over the currently applied Pseudomonad enzyme.

Research Support, Non-U.S. Gov'ts

Exchange of the VP5 of Infectious Bursal Disease Virus in a Serotype I Strain with that of a Serotype II Strain Reduced the Viral Replication and Cytotoxicity: Liting Qin , Xiaole Qi , Honglei Gao , Yulong Gao , Zhigao Bu , Xiaomei Wang; J. Microbiol. 2009;47(3):344-350. Published online June 26, 2009; DOI: https://doi.org/10.1007/s12275-009-0028-7

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Abstract: Infectious bursal disease virus (IBDV), belonging to Avibirnavirus genus in the Birnaviridae family, consists of two segments of double-strand RNA. There are two distinct serotypes of IBDV, the pathogenic serotypeI and the non-pathogenic serotype II. Comparison of the deduced amino acid sequences of a panel of VP5 genes retrieved from GenBank revealed a high identity among strains within the serotype I or serotypeII group but a low identity between strains across two serotypes. In this study, we rescued two mosaic viruses, rGtGxVP5 and rGt2382VP5 by exchanging the VP5 gene of a cell culture-adapted serotype I Gt strain with its counterpart of the very virulent IBDV Gx strain, or a non-pathogenic 23/82 strain of the serotype II. In comparison to the parental strain rGt virus, the rGtGxVP5 showed the similar viral replication, cytotoxicity and the ability of inducing apoptosis; however, the other mosaic virus rGt2382VP5 had a lower titer and a reduced cytotoxicity. Although exchange of VP5 within serotype I group did not alter the viral replication and cytotoxicity of Gt strain, exchange of VP5 in the serotype I with that of a serotypeII reduced the viral replication and cytotoxicity on chicken embryo fibroblast (CEF) cells. Therefore, the VP5 of serotype II may be one of the factors responsible for the distinct pathogenic features of two serotypes.

Isolation and Identification of an Anticancer Drug, Taxol from Phyllosticta tabernaemontanae, a Leaf Spot Fungus of an Angiosperm, Wrightia tinctoria: Rangarajulu Senthil Kumaran , Johnpaul Muthumary , Byung-Ki Hur; J. Microbiol. 2009;47(1):40-49. Published online February 20, 2009; DOI: https://doi.org/10.1007/s12275-008-0127-x

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Abstract: Phyllosticta tabernaemontanae, a leaf spot fungus isolated from the diseased leaves of Wrightia tinctoria, showed the production of taxol, an anticancer drug, on modified liquid medium (M1D) and potato dextrose broth (PDB) medium in culture for the first time. The presence of taxol was confirmed by spectroscopic and chromatographic methods of analysis. The amount of taxol produced by this fungus was quantified using high performance liquid chromatography (HPLC). The maximum amount of taxol production was recorded in the fungus grown on M1D medium (461 ug/L) followed by PDB medium (150 ug/L). The production rate was increased to 9.2x103 fold than that found in the culture broth of earlier reported fungus, Taxomyces andreanae. The results designate that P. tabernaemontanae is an excellent candidate for taxol production. The fungal taxol extracted also showed a strong cytotoxic activity in the in vitro culture of tested human cancer cells by apoptotic assay.

Protective Effect of Polygoni Cuspidati Radix and Emodin on Vibrio vulnificus Cytotoxicity and Infection: Jong Ro Kim , Dool-Ri Oh , Mi Hye Cha , Byoung Sik Pyo , Joon Haeng Rhee , Hyon E. Choy , Won Keun Oh , Young Ran Kim; J. Microbiol. 2008;46(6):737-743. Published online December 24, 2008; DOI: https://doi.org/10.1007/s12275-008-0232-x

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Abstract: Vibrio vulnificus, a good model organism of bacterial septicemia, causes fatal septicemia manifesting a fulminating course and a high mortality rate within days. In order to identify new natural substances preventing V. vulnificus infection, a plant library was screened for inhibiting cytotoxicity to host cells by using Trypan blue staining and LDH assay. We found that Polygoni Cuspidati Radix potently suppressed the acute death of HeLa and RAW264.7 cells in a dose dependent manner. Further studies revealed that Polygoni Cuspidati Radix inhibited V. vulnificus growth and survival in HI broth and seawater, respectively. We confirmed that Polygoni Cuspidati Radix contained high level of emodin by thin layer chromatography (TLC). Emodin showed direct antibacterial activity against V. vulnificus. In addition, emodin prevented the morphologic damages and acute death of HeLa cells caused from V. vulnificus. The safety of Polygoni Cuspidati Radix and emodin to host cells was confirmed by MTT assay. Polygoni Cuspidati Radix and emodin protected mice from V. vulnificus infection.

Identification and Characterization of the Vibrio vulnificus rtxA Essential for Cytotoxicity in vitro and Virulence in Mice: Jeong Hyun Lee , Myung Won Kim , Byoung Sik Kim , Seung Min Kim , Byung Cheol Lee , Tae Sung Kim , Sang Ho Choi; J. Microbiol. 2007;45(2):146-152.; DOI: https://doi.org/2520 [pii]

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Abstract: A mutant exhibiting decreased cytotoxic activity toward INT-407 intestinal epithelial cells and carrying a mutation in the rtx gene cluster that consists of rtxCA and rtxBDE operons was screened from a library of V. vulnificus mutants. The functions of the rtxA gene, assessed by constructing an isogenic mutant and evaluating its phenotypic changes, demonstrated that RtxA is essential for the virulence of V. vulnificus in mice as well as in tissue cultures.

Tumor Necrosis Factor Receptor (TNFR)-associated factor 2 (TRAF2) is not Involved in GM-CSF mRNA Induction and TNF-Mediated Cytotoxicity: Kim, Jung Hyun , Cha, Myung Hoon , Lee, Tae Kon , Seung, Hyo Jun , Park, Choon Sik , Chung, Il Yup; J. Microbiol. 1999;37(2):111-116.

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Abstract: Tumor necrosis factor receptor (TNFR)-associated factor 2 (TRAF2) is known to act as a signal transducer that connects TNFR2 to its downstream effector functions such as proliferation of thymocytes, regulation of gene expression, and cell death. TRAF2 consists of largely two domains, the N-terminal half that contains a signal-emanating region and the C-terminal half that is responsible for binding to the intracellular region of TNFR2. In this study, we examined the possible roles of TRAF2 in granulocyte-macrophage colony-stimulating factor (GM-CSF) gene expression and cell death. A truncated mutant of TRAF2 (Δ2-263) that contains only a C-terminal half was generated, and transiently transfected to the A549 cell, a human lung cancer cell line, and L929 cell, a murine TNF-sensitive cell line. GM-CSF mRNA was induced in untransfected A540 cells both in dose- and time-dependent manner upon the exposure of TNF. However, neither the full length TRAF2 nor the mutant altered GM-CSF mRNA production regardless of the presence or absence of TNF. Furthermore, neither TRAF2 versions significantly changed the cytotoxic effect of TNF on L929 cells. These data suggest that TRAF2 may not be involved in the signal transduction pathway for GM-CSF gene induction and cell death mediated by TNF.

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