Journal of Microbiology

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

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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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.

A Thermostable Phytase from Neosartorya spinosa BCC 41923 and Its Expression in Pichia pastoris: Patcharaporn Pandee , Pijug Summpunn , Suthep Wiyakrutta , Duangnate Isarangkul , Vithaya Meevootisom; J. Microbiol. 2011;49(2):257-264. Published online May 3, 2011; DOI: https://doi.org/10.1007/s12275-011-0369-x

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Abstract: A phytase gene was cloned from Neosartorya spinosa BCC 41923. The gene was 1,455 bp in size, and the mature protein contained a polypeptide of 439 amino acids. The deduced amino acid sequence contains the consensus motif (RHGXRXP) which is conserved among phytases and acid phosphatases. Five possible disulfide bonds and seven potential N-glycosylation sites have been predicted. The gene was expressed in Pichia pastoris KM71 as an extracellular enzyme. The purified enzyme had specific activity of 30.95 U/mg at 37°C and 38.62 U/mg at 42°C. Molecular weight of the deglycosylated recombinant phytase, determined by SDS-PAGE, was approximately 52 kDa. The optimum pH and temperature for activity were pH 5.5 and 50°C. The residual phytase activity remained over 80% of initial activity after the enzyme was stored in pH 3.0 to 7.0 for 1 h, and at 60% of initial activity after heating at 90°C for 20 min. The enzyme exhibited broad substrate specificity, with phytic acid as the most preferred substrate. Its Km and Vmax for sodium phytate were 1.39 mM and 434.78 U/mg, respectively. The enzyme was highly resistant to most metal ions tested, including Fe2+, Fe3+, and Al3+. When incubated with pepsin at a pepsin/phytase ratio of 0.02 (U/U) at 37°C for 2 h, 92% of its initial activity was retained. However, the enzyme was very sensitive to trypsin, as 5% of its initial activity was recovered after treating with trypsin at a trypsin/phytase ratio of 0.01 (U/U).

Molecular Cloning of the Phospholipase D Gene from Streptomyces sp. YU100 and Its Expression in Escherichia coli: Ji-Seon Lee , Munkhtsetseg Bat-Ochir , Atanas V. Demirev , Doo Hyun Nam; J. Microbiol. 2009;47(1):116-122. Published online February 20, 2009; DOI: https://doi.org/10.1007/s12275-008-0161-8

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Abstract: The gene for phospholipase D (PLD) of Streptomyces sp. YU100 was cloned from λ phage library and heterologously expressed in Escherichia coli. Using an amplified gene fragment based on the consensus sequences of streptomycetes PLDs, λ phage library of Streptomyces sp. YU100 chromosomal DNA was screened. The sequencing result of BamHI-digested 3.8 kb fragment in a positive phage clone revealed the presence of an open reading frame of a full sequence of PLD gene encoding a 540-amino acid protein including 33-amino acid signal peptide. The deduced amino acid sequence showed a high homology with other Streptomyces PLDs, having the highly conserved ‘HKD’ motifs. The PLD gene excluding signal peptide sequence was amplified and subcloned into a pET-32b(+) expression vector in E. coli BL21(DE3). The recombinant PLD was purified by nickel affinity chromatography and compared the enzyme activity with wild-type PLD. The results imply that the recombinant PLD produced by E. coli had the nearly same enzyme activity as PLD from Streptomyces sp. YU100.

Cloning of the gense coding for extracellular proteases from alkalophilic xanthomonas SP. JK311: Kim, Young Hun , Jang, Ji Yeon , Yeeh, Yeehn , Kim, Yong Ho , Kim, Sang Hae; J. Microbiol. 1995;33(4):344-349.

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Abstract: The alkalophilic bacterium, Xanthomonas sp. JK311, producing extracellular proteases, was isolated from soil. Xanthomonas sp. JK311 produced five extracellular proteases that are all metalloproteases. Four of them were resistant against 1% SDS. Chromosomal DNA of the Xanthomonas sp. JK311 was digested with BamHI and cloned into PUC19. Among E. coli strain HB101 transformants, a clone secreting the proteases was screened through halo formation on skim-milk agar plate and by Southern blot analysis. It had the recombinant plasmid pXEP-1 containing the 7.5 kb-BamHI DNA fragment and produced three extacellular proteases. Their protease properties corresponded to those of Xanthomonas sp. JK311.

Molecular Cloning and Analysis of Sporulation-Specific Glucoamylase (SGA) Gene of Saccharomyces diastaticus: Kang, Dae Ook , Hwang, In Kyu , Oh, Won Keun , Lee, Hyun Sun , Ahn, Cheol Soon , Kim, Bo Yeon , Mheen, Tae Ick , Ahn, Hong Seog; J. Microbiol. 1999;37(1):35-40.

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Abstract: Sporulation-specific glucoamylase (SGA) gene was isolated from genomic library of Saccharomyces diastaticus 5114-9A by using glucoamylase non-producing mutant of S. diastaticus as a recipient. When the glucoamylase activities of culture supernatant, periplasmic, and intracellular fraction of cells transformed with hybrid plasmid containing SGA gene were measured, the highest activity was detected in culture supernatant. SGA produced by transformant and extracellular glucoamylase produced by S. diastaticus 5114-9A differed in enzyme characteristics such as optimum temperature, thermostability, and resistance to SDS and urea. But the characteristics of SGA produced by sporulating yeast cells and vegetatively growing transformants were identical.

Molecular Cloning of the Superoxide Dismutase Gene from Orientia tsutsugamushi, the Causative Agent of Scrub Typhus: Ji-Hyun Yun , Young-Sang Koh , Se-Jae Kim; J. Microbiol. 2002;40(2):151-155.

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Abstract: A superoxide dismutase (SOD) gene from the obligate intracellular bacterium Orientia tsutsugamushi has been cloned by using the polymerase chain reaction with degenerate oligonucleotide primers corresponding to conserved regions of known SODs. Nucleotide sequencing revealed that the predicted amino acid sequence was significantly more homologous to known iron-containing SODs (FeSOD) than to manganese-containing SODs (MnSOD). Conserved regions in bacterial FeSOD could also be seen. Isolation of the oriential SOD gene may provide an opportunity to examine its role in the intracellular survival of this bacterium.

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