Journal of Microbiology

Journal Articles

[Protocol]Construction of a multicopy genomic DNA library and its application for suppression analysis: Hongbaek Cho; J. Microbiol. 2019;57(12):1041-1047. Published online November 22, 2019; DOI: https://doi.org/10.1007/s12275-019-9417-8

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Abstract: Suppression analysis is used for the identification of new genes and genetic interactions when there is a notable phenotype available for genetic selection or screening. A random genomic DNA library constructed on a multi-copy plasmid is a useful tool for suppression analysis when one expects that an overdose of a few genes will suppress the phenotype. These libraries have been successfully used to determine the function of a gene by revealing genes whose functions are related to the gene of interest. They have also been used to identify the targets of chemical or biological agents by increasing the number of unaffected target gene products in a cell. In this article, I will discuss important considerations for constructing multicopy genomic DNA libraries. The protocol provided in this paper should be a useful guide for constructing genomic DNA libraries in many bacterial species for which multi-copy plasmids are available.

Antimicrobial effect and proposed action mechanism of cordycepin against Escherichia coli and Bacillus subtilis: Qi Jiang , Zaixiang Lou , Hongxin Wang , Chen Chen; J. Microbiol. 2019;57(4):288-297. Published online March 30, 2019; DOI: https://doi.org/10.1007/s12275-019-8113-z

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40 Citations

Abstract: The detailed antibacterial mechanism of cordycepin efficacy against food-borne germs remains ambiguous. In this study, the antibacterial activity and action mechanism of cordycepin were assessed. The results showed that cordycepin effectively inhibited the growth of seven bacterial pathogens including both Gram-positive and Gram-negative bacterial pathogens; the minimum inhibitory concentrations (MIC) were 2.5 and 1.25 mg/ml against Escherichia coli and Bacillus subtilis, respectively. Scanning electron microscope and transmission electron microscope examination confirmed that cordycepin caused obvious damages in the cytoplasmatic membranes of both E. coli and B. subtilis. Outer membrane permeability assessment indicated the loss of barrier function and the leakage of cytoplasmic contents. Propidium iodide and carboxyfluorescein diacetate double staining approach coupled with flow cytometry analysis indicated that the integrity of cell membrane was severely damaged during a short time, while the intracellular enzyme system still remained active. This clearly suggested that membrane damage was one of the reasons for cordycepin efficacy against bacteria. Additionally, results from circular dichroism and fluorescence analysis indicated cordycepin could insert to genome DNA base and double strand, which disordered the structure of genomic DNA. Basis on these results, the mode of bactericidal action of cordycepin against E. coli and B. subtilis was found to be a dual mechanism, disrupting bacterial cell membranes and binding to bacterial genomic DNA to interfere in cellular functions, ultimately leading to cell death.

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

NOTE] A Rapid PCR-Based Approach for Molecular Identification of Filamentous Fungi: Yuanyuan Chen , Bernard A. Prior , Guiyang Shi , Zhengxiang Wang; J. Microbiol. 2011;49(4):675-679. Published online September 2, 2011; DOI: https://doi.org/10.1007/s12275-011-0525-3

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13 Citations

Abstract: In this study, a novel rapid and efficient DNA extraction method based on alkaline lysis, which can deal with a large number of filamentous fungal isolates in the same batch, was established. The filamentous fungal genomic DNA required only 20 min to prepare and can be directly used as a template for PCR amplification. The amplified internal transcribed spacer regions were easy to identify by analysis. The extracted DNA also can be used to amplify other protein-coding genes for fungal identification. This method can be used for rapid systematic identification of filamentous fungal isolates.

Identification of the Genes Involved in 1-Deoxynojirimycin Synthesis in Bacillus subtilis MORI 3K-85: Kyung-Don Kang , Yong Seok Cho , Ji Hye Song , Young Shik Park , Jae Yeon Lee , Kyo Yeol Hwang , Sang Ki Rhee , Ji Hyung Chung , Ohsuk Kwon , Su-Il Seong; J. Microbiol. 2011;49(3):431-440. Published online June 30, 2011; DOI: https://doi.org/10.1007/s12275-011-1238-3

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34 Citations

Abstract: 1-Deoxynojirimycin (DNJ), a D-glucose analogue with a nitrogen atom substituting for the ring oxygen, is a strong inhibitor of intestinal α-glucosidase. DNJ has several promising biological activities, including its antidiabetic, antitumor, and antiviral activities. Nevertheless, only limited amounts of DNJ are available because it can only be extracted from some higher plants, including the mulberry tree, or purified from the culture broth of several types of soil bacteria, such as Streptomyces sp. and Bacillus sp. In our previous study, a DNJ-producing bacterium, Bacillus subtilis MORI, was isolated from the traditional Korean fermented food Chungkookjang. In the present study, we report the identification of the DNJ biosynthetic genes in B. subtilis MORI 3K-85 strain, a DNJ-overproducing derivate of the B. subtilis MORI strain generated by γ-irradiation. The genomic DNA library of B. subtilis MORI 3K-85 was constructed in Escherichia coli, and clones showing α-glucosidase inhibition activity were selected. After DNA sequencing and a series of subcloning, we were able to identify a putative operon which consists of gabT1, yktc1, and gutB1 genes predicted to encode putative transaminase, phosphatase, and oxidoreductase, respectively. When a recombinant plasmid containing this operon sequence was transformed into an E. coli strain, the resulting transformant was able to produce DNJ into the culture medium. Our results indicate that the gabT1, yktc1, and gutB1 genes are involved in the DNJ biosynthetic pathway in B. subtilis MORI, suggesting the possibility of employing these genes to establish a large-scale microbial DNJ overproduction system through genetic engineering and process optimization.

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