Journal of Microbiology

Journal Article

Metabolism-mediated induction of zinc tolerance in Brassica rapa by Burkholderia cepacia CS2-1: Sang-Mo Kang , Raheem Shahzad , Saqib Bilal , Abdul Latif Khan , Young-Hyun You , Won-Hee Lee , Hee-La Ryu , Ko-Eun Lee , In-Jung Lee; J. Microbiol. 2017;55(12):955-965. Published online December 7, 2017; DOI: https://doi.org/10.1007/s12275-017-7305-7

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Brassica rapa (Chinese cabbage) is an essential component of traditional Korean food. However, the crop is often subject to zinc (Zn+) toxicity from contaminated irrigation water, which, as a result, compromises plant growth and production, as well as the health of human consumers. The present study investigated the bioaccumulation of Zn+ by Burkholderia cepacia CS2-1 and its effect on the heavy metal tolerance of Chinese cabbage. Strain CS2-1 was identified and characterized on the basis of 16S rRNA sequences and phylogenetic analysis. The strain actively produced indole-3-acetic acid (3.08 ± 0.21 μg/ml) and was also able to produce siderophore, solubilize minerals, and tolerate various concentrations of Zn+. The heavy metal tolerance of B. rapa plants was enhanced by CS2-1 inoculation, as indicated by growth attributes, Zn+ uptake, amino acid synthesis, antioxidant levels, and endogenous hormone (ABA and SA) synthesis. Without inoculation, the application of Zn+ negatively affected the growth and physiology of B. rapa plants. However, CS2-1 inoculation improved plant growth, lowered Zn+ uptake, altered both amino acid regulation and levels of flavonoids and phenolics, and significantly decreased levels of superoxide dismutase, endogenous abscisic acid, and salicylic acid. These findings indicate that B. cepacia CS2-1 is suitable for bioremediation against Zn+-induced oxidative stress.

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

Safety Evaluation of Lactobacillus paracasei subsp. paracasei LC-01, Probiotic Bacterium: Hao Zhang , Yu Wang , Jing Sun , Zirui Guo , Huiyuan Guo , Fazheng Ren; J. Microbiol. 2013;51(5):633-638. Published online October 31, 2013; DOI: https://doi.org/10.1007/s12275-013-3336-x

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Abstract

The safety of Lactobacillus paracasei subsp. paracasei LC-01 was evaluated for its use as a potential probiotic. In our in vitro study, the antibiotic resistance and the ability to produce biogenic amine were determined. The results showed that the strain was sensitive to all tested antibiotics and did not produce biogenic amine except for tyramine. The oral toxicity of this strain was evaluated in Balb/C mice. One hundred mice were divided into 10 groups. Four groups were administered 0, 108, 109, or 1010 CFU/mouse per day dissolved in saline solution respectively, for 28 days. Three groups were injected intraperitoneally with 109 CFU/mouse dissolved in saline solution, and were killed 2, 5, and 10 days after injection. The last 3 groups were injected with the vehicle as controls respectively. The results showed that oral administration of the strain had no adverse effects on mouse body weight and that there was no treatment-associated bacterial translocation. Intraperitoneal administration caused a significant translocation to liver, spleen and kidney. However, this translocation did not cause illness or death throughout the experiment. The results suggest that L. paracasei subsp. paracasei LC-01 is likely to be safe for human consumption.

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NOTE] Quantification of Toxic Effects of the Herbicide Metolachlor on Marine Microalgae Ditylum brightwellii (Bacillariophyceae), Prorocentrum minimum (Dinophyceae), and Tetraselmis suecica (Chlorophyceae): Vinitha Ebenezer , Jang-Seu Ki; J. Microbiol. 2013;51(1):136-139. Published online March 2, 2013; DOI: https://doi.org/10.1007/s12275-013-2114-0

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Abstract: Toxic effects of the herbicide metolachlor (MC) were evaluated for three marine microalgae, Tetraselmis suecica (chlorophyte), Ditylum brightwellii (diatom), and Prorocentrum minimum (dinoflagellate). MC showed a significant reduction in cell counts and chlorophyll a levels. Median effective concentration (EC50) was calculated based on chlorophyll a levels after a 72-h MC exposure. EC50 values for T. suecica, D. brightwellii, and P. minimum were 21.3, 0.423, and 0.07 mg/L, respectively. These values showed that the dinoflagellate was most sensitive when exposed to the herbicide, at a concentration comparable to freshwater algae, suggesting its potential as an appropriate model organism for ecotoxicity assessments in marine environments.

Review

REVIEW] The Role of Type III Secretion System 2 in Vibrio parahaemolyticus Pathogenicity: Hyeilin Ham , Kim Orth; J. Microbiol. 2012;50(5):719-725. Published online November 4, 2012; DOI: https://doi.org/10.1007/s12275-012-2550-2

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Abstract: Vibrio parahaemolyticus, a Gram-negative marine bacterial pathogen, is emerging as a major cause of food-borne illnesses worldwide due to the consumption of raw seafood leading to diseases including gastroenteritis, wound infection, and septicemia. The bacteria utilize toxins and type III secretion system (T3SS) to trigger virulence. T3SS is a multi-subunit needle-like apparatus used to deliver bacterial proteins, termed effectors, into the host cytoplasm which then target various eukaryotic signaling pathways. V. parahaemolyticus carries two T3SSs in each of its two chromosomes, named T3SS1 and T3SS2, both of which play crucial yet distinct roles during infection: T3SS1 causes cytotoxicity whereas T3SS2 is mainly associated with enterotoxicity. Each T3SS secretes a unique set of effectors that contribute to virulence by acting on different host targets and serving different functions. Emerging studies on T3SS2 of V. parahaemolyticus, reveal its regulation, translocation, discovery, characterization of its effectors, and development of animal models to understand the enterotoxicity. This review on recent findings for T3SS2 of V. parahaemolyticus highlights a novel mechanism of invasion that appears to be conserved by other marine bacteria.

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.

Diversity and Metal Tolerance of Nematode-Trapping Fungi in Pb-Polluted Soils: Ming-He Mo , Wei-Min Chen , Hao-Ran Yang , Ke-Qin Zhang; J. Microbiol. 2008;46(1):16-22.; DOI: https://doi.org/10.1007/s12275-007-0174-8

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Abstract: The diversity of nematode-trapping fungi (NTF) in two lead (Pb) mines in Yunnan Province, China was investigated in 2004. In total, 20 species belonging to five genera were identified from 500 samples collected at the Lanping and the Huize mines. Pb concentrations ranged from 216~7,150 mg/kg for the former and 132~13,380 mg/kg for the latter, respectively. The fungi were divided into five groups based on different trapping mechanisms. The trapping-net producer group contained the largest number of species, with nine. Two predators, Dactylellina ellipsosporum and Arthrobotrys oligospora, were found at frequencies of 32.85% and 15.41%, respectively. The diversity indexes of NTF were positively correlated with Pb pollution levels in both the Lanping Mine (r=0.66) and the Huize Mine (r=0.72), suggesting that the distribution of NTF was not negatively affected by Pb contamination. For most strains of a given species, there was no significant difference (P>0.01) in the Pb tolerance between the strains isolated from habitats with low or high Pb concentrations. However, Pb toxicity exerted adverse effects on trap formation and predacious capability of fungi. We discuss the possible metal tolerance mechanisms and their relationships to the survival strategy of NTF in Pb-polluted environments.

Degradation of collagens, immunoglobulins, and other serum proteins by protease of salmonella schottmulleri and its toxicity to cultured cells: Na, Byoung Kuk , Kim, Moon Bo , Song, Chul Yong; J. Microbiol. 1996;34(1):95-100.

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Abstract: The effect of the extracellular protease of Salmonella schottmulleri on human serum constituents such as immunoglobulins, hemoglobin and lysozyme and tissue constituents such as fibronectin and collagens was investigated. This protease degraded collagens (type I and III), fibronectin and serum proteins such as human hemoglobin and lysozyme. Bovine serum albumin was degraded slightly. Thus, the present study suggested the possibility that this protease is not only played an important role in invasion of S. schottmulleri by degrading the constituent proteins such as collagens and fibronectin but also induced complications observed in septicemia and chronic infections by degrading the serum proteins. This protease is also capable of degrading defence-oriented humoral proteins, immunoglobulins (IgG and IgM). Furthermore, it is toxic to HEp-2 cells. These findings clarified the possible role of Salmonella protease as a virulence factor in the pathogenesis of Salmonella infections.

Isolation and Characterization of Pigment-deficient Mutants from Azomonas agilis PY101: You, Kyung Man , Lee, Sang Hyeon , Park, Yong Keun; J. Microbiol. 1999;37(1):45-49.

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Abstract: To investigate the mechanism of cadmium tolerance in a cadmium-resistant Azomonas agilis PY101 that produces a specific fluorescent pigment promoted by cadmium, we carried out Tn5 mutagenesis and isolated four pigment-deficient mutants. In these mutants, Ppg1, Ppg2, and Ppg3 remarkably reduced the pigment production to 15.3%, 11.2%, and 13.9%, respectively. Especially, Ppg4 mutant did not produce the pigment at all. None of the mutants grew in the presence of 1500 ppm of CdCl₂in growth medium, and they exhibited differential sensitivities to cadmium. Ppg1, Ppg2, Ppg3, and Ppg4 mutants were sensitive to 900 ppm, 1100 ppm, 1000 ppm, and 800 ppm of CdCl2, respectively. These mutants also showed noticeable increase, from 8.8-fold to 13.2-fold, in the size of growth inhibition zone compared with that of the will type after treatment with cadmium. Therefore, the pigment production of A. agilis PY101 was found to decrease the toxic effects of cadmium to the bacterium.

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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