• International Journal of Industrial Entomology and Biomaterials
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• v.1 no.1
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• pp.9-17
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• 2000

Genetic variation in the domestic silkworm strains (Bombyx mori) and phylogenetic relationships between domestic silkworms and wild silkworms (B. mandarina) were investigated by using a portion of mitochondrial CGI gene sequences. Ten geographic strains of B. mori we sequenced were identical in the 410 bp-section of mitochondrial COI gene. This sequence was also identical to the homologous sequence of the four Gen-Bank-registered strains, but one strain of B. mori differed a single nucleotide (0.2%) from others. MtDNA homogeneity in the B. mori strains appears to be resulted from fixation into the mast frequent mtDNA type during the course of breeding for new strains, in which an extensive indoor rearing and removal of unwanted individuals were accompanied. In the comparisons between domestic and wild silkworms, some wild silkworms were closely related to domestic silkworms (0.2%-1.2% of divergence), but the others were not (2.7%-3.7% of sequence divergence). This result was also reflected in the phylogenetic analyses, showing two independent phylogenetic groups: one including all B. mandarina sequences and the other including both B. mandarina and B. mori sequences. Thus, domestic silkworms may have been derived from the ancestor of B. mandarina, which belongs to this group, alto-ough more extensive study will provide better understanding on this issue.

• Journal of Life Science
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• v.27 no.3
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• pp.339-345
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• 2017

Carotenoids are natural lipid-soluble pigments, which are produced primarily by bacteria, algae, and plants. Many studies have focused on the identification, production, and utilization of natural sources of astaxanthin from algae, yeast, and crustacean byproducts as an alternative to the synthetic pigment, which is mostly used today. The aim of the present study was to identify a mutant of Paracoccus haeundaensis by exposure to UV and ethyl methanesulfonate (EMS). The mutant was then exposed to nutrient stress conditions to isolate an astaxanthin-hyperproducing strain, followed by characterization of the mutant. The survival rate decreased in accordance with an increase in the UV exposure time and an increase in the EMS concentration. A mutant of the original P. haeundaensis strain was identified that showed hyperproduction of astaxanthin following exposure to UV irradiation (20 min) and EMS treatment (0.4 M concentration). The optimal culture conditions for the PUE mutant were $25^{\circ}C$, pH 7-8, and 3% NaCl. The effects of various carbon and nitrogen sources on the growth and astaxanthin production of PUE were examined. The addition of 1% raffinose and 3% potassium nitrate influenced cell growth and astaxanthin production. The selected mutant exhibited an increase of 1.58 folds in astaxanthin content compared to initial wild type strain. A genetically stable mutant strain obtained using mutagen (UV irradiation and EMS treatment) may be a suitable candidate for further industrial scale production of astaxanthin.

• Journal of Microbiology and Biotechnology
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• v.20 no.2
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• pp.281-286
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• 2010

A Pseudomonas fluorescens strain was isolated and found to show antagonistic activity against phytopathogenic fungi and to possess a gene responsible for production of antibiotic 2,4-diacetylphloroglucinol. For the extension of biocontrol range, a gene for an Androetonus australis Hector insect toxin 1 (AaHIT1), one of the most known toxic insect-selective peptides, was designed and synthesized according to the preferred codon usage of Pseudomonas fluorescens, cloned, and transformed into the strain by pSUP106 vector, a broad-host-range plasmid. Bioassays indicated that the engineered strain was able to produce AaHIT1 with insecticidal activity, and at the same time retain the activity against plant pathogen. The experiments for nonplanted soil and rhizosphere colonization showed that, similar to the population of the wild-type strain, that of the engineered strain remained relatively constant in the first 10 days, and the subsequent 50 days, suggesting that AaHIT1 expression in the bacterial cell does not substantially impair its long-term colonization. It is first reported that a Pseudomonas fluorescens strain expressing an active scorpion neurotoxin has dual activity against phytopathogenic fungi and insects, making at attractive for agronomic applications.

• Microbiology and Biotechnology Letters
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• v.40 no.1
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• pp.10-16
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• 2012

The Streptomyces peucetius OIM (Overproducing Industrial Mutant) strain is a recursively-mutated and optimally-screened strain used for the industrial production of polyketide antibiotics, such as doxorubicin (DXR). Using the S. peucetius OIM mutant strain as a surrogate host, a model minimal polyketide pathway for aloesaponarin II, an actinorhodin shunt product, was cloned in a high-copy conjugative plasmid, followed by functional pathway expression and quantitative metabolite analysis. The level of aloesaponarin II production was noted as being significantly higher in the OIM strain than in the wild-type S. peucetius, as well as in the regulatory network-stimulated S. coelicolor mutant strain. Moreover, the aloesaponarin II production level was seen to be even higher in a down-regulator $wblA_{spe}$-deleted S. peucetius OIM strain, implying that the rationally-engineered S. peucetius OIM mutant strain could be used as an efficient surrogate host for the high expression of foreign polyketide pathways.

• Journal of fish pathology
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• v.20 no.3
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• pp.221-227
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• 2007

In this study, one hundred strains of bacterial flora were isolated from the intestine of cultured and wild black rockfish Sebastes inermis collected in Yeosu and examined for drug resistance to 9 antibiotics. From cultrued fish, the isolated bacteria were Photobacterium group (26 strains) and Acinetobacter group (18 strains) of Gram-negative, and unidentified marine sediment bacterium (6 strains) of Gram-positive. From wild fish, Photobacterium group (18 strains), Acinetobacter group (12 strains) and Shewanella group (5 strains) of Gram-negative and Bacillus group (8 strains), Staphylococcus group (4 strains), and unidentified marine sediment bacterium (3 strains) of Gram-positive. Intestine flora of wild black rockfish was more diverse than that of one cultured. The drugs tested were tetracyclines (oxytetracycline), aminoglycosides (gentamicin), macrorides (erythromycin) and quinolones (flumequine, oxolinic acid, norfloxacin, ofloxacin, enrofloxacin and ciprofloxacin). Sensitivity to all seven antibiotics except oxytetracycline and oxolinic acid was higher in bacteria from wild fish than from cultured ones, although wild isolates were more resistant than control strain Escherichia coli ATCC9637. This suggests that use of antibiotics in the fish farm might have some resistance in intestinal flora of wild fish.

• Journal of Microbiology and Biotechnology
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• v.28 no.10
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• pp.1769-1769
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• 2018

• Korean Journal of Microbiology
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• v.27 no.2
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• pp.124-129
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• 1989

In order to improve the production of bacterial alginate, Azotobacter vinelandii NCIB 8789 was treated with 200.$\mu$g/ml of MNNG for obtaining mutant strain. The mutant HB18 was selected, which produced the highest amount of alginic acid among the survival stains. The HB18 produced 5.4g/l of alginic acid when batch cultured at $30^{\circ}C$ for 160 hrs and its alginic acid showed high molecular weight and simple composition when compared with thoseof wild type.

• Journal of Life Science
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• v.10 no.1
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• pp.45-47
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• 2000

Nonactin, known as an ionophore antibiotic, was antagonized by the actibity of quercetin, an oxygen radical scavenger. This compound generated superoxide radicals in Bacillus subtilis lysates. A recombination-deficient mutant strain of B. subtilis was more sensitive than a wild strain, and this hypersensitivity was reduced in the presence of dithiothreitol as an antioxidant. These results suggest that superoxide radical is important in the antibacterial action of this agent.

• KSBB Journal
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• v.6 no.3
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• pp.223-230
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• 1991

Using the shuttle vector pECCGl between Escherichia coli and Corynebacterium glutamicum and C. glutamicum strain JS231 grown in the medium supplemented with penicillin-G, which inhibits the formation of cross-links in the peptidoglycan of bacterial cell wall, various parameters involved in electroporation system including resistance, electric field strength, capacitance, DNA concentration, and cell density were investigated independently and optimized for the high efficiency transformation of coryneform bacteria. Using cells grown with 0.3U/ml of penicillin-G and harvested at A600 of 0.7-0.8, transformation efficiencies of 107-l08 transformants/$\mu\textrm{g}$ of DNA with Corynebcctertum glutamicum strain JS231 and wild type ATCC13032 were achieved under conditions of 12.5kV/cm of electric field strength, 400 ohms of resistance, $25\mu$F of capacitance, 3$\times$108 cells per transformation(1.2$\times$1010 cells/ml) and 100ng of plasmid DNA per transformation.

• Asian-Australasian Journal of Animal Sciences
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• v.7 no.4
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• pp.509-512
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• 1994

High performance liquid chromatography (HPLC) analysis was applied for determination of guanine plus cytosine (G + C) contents of DNA of Butyrivibrio fibrisolvens. By values of G + C contents, a reference strain and 20 wild strains of B. fibrisolvens were classified into at least two distinct subgroups, i.e. G + C contents of 18 strains were 38-40 mol% and those of 3 strains including the reference strain were 43-45 mol%. Clear relationships were not observed between G + C contents and biological properties of 21 strains of B. Fibrisolvens.