• Korean Journal of Pharmacognosy
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• v.34 no.1 s.132
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• pp.80-85
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• 2003

Water extract from Astragali Radix (AR) was tested for the safety using Ames, Bacillus subtilis Rec, and umu gene expression mutagenicity tests. Mutagenic activity in any assays we tested was not found. In Ames test, Salmonella typhimurium TA98 and TA 100 were used to identify mutagenic property, and the number of histidine revertants was measured. In the Recassay, Bacillus subtilis ${H-17(Rec^+)\;and\;M-45(Rec^-)}$ strains were used to test DNA damage activity. In the SOS umu test, Salmonella typhimurium TA1535 containing plasmid pSK1002 was used as a test strain, and we monitored the levels of umu operon expression by measuring the ${\beta}-galactosidase$ activity. From the results, there was no DNA damage and mutagenicity of AR. Hepatotoxicity of AR to female ICR mice was also monitored by the measurements of s-GOT, s-GPT, LDH activities after oral feeding for 15 days. AR was not shown any significant changes of s-GOT, s-GPT and LDH activities in mice sera.

• Korean Journal Plant Pathology
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• v.14 no.4
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• pp.350-357
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• 1998

A total of 12 strains of fluorescent Pseudomonas isolated from the cultivated mushrooms such as Agaricus bisporus and Pleurotus ostreatus were collected. They consisted of pathogenic Pseudomonas spp. and epiphytic Pseudomonas spp. of the cultivated mushroom. To analyze the phylogenetic relationship of these strains, ITS I region, the 16S-23S intergenic spacer region in the ribosomal RNA (rRNA) operon, was cloned and sequenced. The spacer regions of these strains were 495∼527 nucleotides in length and contained the genes encoding isoleucine-tRNA (tRNAIle) and alanine-tRNA (tRNAAla). The reciprocal homologies of each ITS I sequence among these strains were in the range of 84.2%∼98.8%. According to the analysis of ITS I sequences, the fluorescent Pseudomonas spp. were phylogenetically classified into three clusters. Cluster I consisted of Pseudomonas fluorescens, P. tolaasii, P. gingeri’, and P.‘reactans’(WLRO). Cluster II comprised Pseudomonas fluorescens biovar C and F. Cluster III composed P. agarici. Cluster I and II could be classified into P. fluorescens complex. P. agarici formed an independent taxon clearly separable from P. florescens complex.

• Journal of Soil and Groundwater Environment
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• v.21 no.5
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• pp.16-24
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• 2016

A new strain of Pseudomonas sp. was isolated from mercury (Hg)-contaminated sites in Taiwan. This bacterium removed more than 80% of Hg present in the culture medium at 12 h incubation and was chosen for further analysis of the molecular mechanisms of Hg tolerance/removal abilities in this Pseudomonas sp. We used RNA-seq, one of the next-generation sequencing methods, to investigate the transcriptomic responses of the Pseudomonas sp. exposed to 60 mg/L of Hg²⁺. We de novo assembled 4,963 contigs, of which 10,533 up-regulated genes and 5,451 down-regulated genes were found to be regulated by Hg. The 40 genes most altered in expression levels were associated with tolerance to Hg stress and metabolism. Functional analysis showed that some Hg-tolerant genes were related to the mer operon, sulfate uptake and assimilation, the enzymatic antioxidant system, the HSP gene family, chaperones, and metal transporters. The transcriptome were analyzed further with Gene Ontology (GO) and Cluster of Orthologous Groups (COGs) of proteins and showed diverse biological functions and metabolic pathways under Hg stress.

• Journal of Microbiology and Biotechnology
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• v.4 no.1
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• pp.13-19
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• 1994

A model equation to describe the plasmid instability in recombinant Escherichia coli fermentation is proposed. The equation allows one to estimate easily the two model parameters; (1) the difference in the specific growth rates between plasmid-free cells and plasmid-harboring cells ($\delta$), and (2) the probability of plasmid loss by plasmid-harboring cells ($\rho$). The estimated values of $\delta and \rho$ were in the range of 0.02-0.07 and $10^{-3}-10^{-5}$, respectively, and were strongly dependent on the dilution rate. As another parameter, the ratio of specific growth rates of plasmid-free cells and plasmid-harboring cells ($\alha$) was calculated and the result showed the highest value of 1.28 at the lowest dilution rate of 0.075 $hr^{-l}$, examined in this work. By the sensitivity analyses on the estimates of $\delta and \rho$, it was found that the growth rate difference ($\delta$) affected the plasmid instability more seriously than the probability of plasmid loss ($\rho$). Furthermore, the profound instability of plasmid at low dilution rate could be explained by the high values of $\alpha and \rho$.

• Journal of Microbiology and Biotechnology
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• v.16 no.12
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• pp.1912-1918
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• 2006

Marine bacterium Hahella chejuensis KCTC 2396 simultaneously produced red antibiotic prodigiosin and undecylprodiginine. A complete set of the prodigiosin biosynthetic gene cluster has been cloned, sequenced, and successfully expressed in a heterologous host. Sequence analysis of the gene cluster revealed 14 ORFs showing high similarity to pig and red genes from Serratia spp. and Streptomyces coelicolor A3(2), respectively, and the gene organization was almost: similar to that of pig genes. These genes were named hap for Hahella prodigiosin, and determined to be transcribed as a single operon, by RT-PCR experiment. Based on the hap gene mutagenesis experiments and comparative analysis with pig and red genes, we propose a prodigiosin-biosynthetic pathway in KCTC 2396.

• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.1093-1098
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• 2004

An open reading frame encoding CadC, consisting of 526 amino acids, was identified from the upstream region of the Vibrio vulnificus cadBA operon. The deduced amino acid sequences of the cadC were 22 to 78% similar to those reported from other Enterobacteriaceae. Functions of cadC gene on acid tolerance were assessed by comparing acid tolerances of V. vulnificus and its isogenic mutant, whose cadC gene was inactivated by allelic exchanges. The results demonstrated that the gene product of cadC contributes to acid tolerance of V. vulnificus, and that its contribution is dependent on prior exposure of cells to moderately acidic pH. The cellular level of cadB and cadA transcripts decreased in the cadC mutant, indicating that CadC exerts its effect on acid tolerance of V. vulnificus by enhancing the expression of cadBA in a pH-dependent manner.

• Journal of Microbiology and Biotechnology
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• v.19 no.10
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• pp.1127-1134
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• 2009

Escherichia coli excretes acetate during aerobic growth on glycolytic carbon sources, which has been explained as an overflow metabolism when the carbon flux into the cell exceeds the capacity of central metabolic pathways. Nonacetogenic growth of E. coli on gluconeogenic carbon sources like succinate or in carbon-limited slow growth conditions is believed an evidence for the explanation. However, we found that a strain defected in the acs (acetyl Co-A synthetase) gene, the product of which is involved in scavenging acetate, accumulated acetate even in succinate medium and in carbon-limited low growth rate condition, where as its isogenic parental strain did not. The acs promoter was inducible in noncatabolite repression condition, whereas the expression of the ackA-pta operon encoding acetate kinase and phosphotransacetylase for acetate synthesis was constitutive. Results in this study suggest that E. coli excretes and scavenges acetate simultaneously in the carbon-limited low growth condition and in nonacetogenic carbon source, and the activity of the acetate consumption pathway directly affects the accumulation level of acetate in the culture broth.

• Journal of Microbiology and Biotechnology
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• v.11 no.2
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• pp.251-258
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• 2001

In Gram(+) bacteria and organelles in higher eukarotes, $Gln-tRNA^{Gln}$ utilized for protein biosynthesis is formed by a tRNA-dependent amino acid transformation using mischarged $Gln-tRNA^{Gln}$ as the intermediate. In this study, the gatCAB gene encoding $Gln-tRNA^{Gln}$ amidotransferase (Glu-AdT) of Staphylococcus aureus was cloned and its nucleotide sequence wa determined. The S. aureus gatCAB gene was organized in an operon structure consisting of three open reading frames (gatC, gatA, and gatB), similar to that of Bacillus subtilis. The gene sequences for the A and B subunits of$Gln-tRNA^{Gln}$ amidotransferase showed significant homology (77 and 87% homology with amino acid sequence) with the gatA and gatB genes of B. subtilis, yet the C subunit (gatC) showed a relatively lowe homology with the B. subtilis gatC gene and other orthologues. The cloned S. aureus <$Gln-tRNA^{Gln}$ amidotransferase gene was highly expressed in Escherichia coli, and the resulting crude enzyme could convert misacylated <$Gln-tRNA^{Gln}$ into $Gln-tRNA^{Gln}$ in vitro.

• Journal of Microbiology and Biotechnology
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• v.10 no.1
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• pp.63-68
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• 2000

GroEL is well known as a molecular chaperone. In order to determine the dynamic stress response of the Escherichia coli groE promoter, a groE-lacZ operon fusion in the chromosome was constructed. Stress leading to ${\sigma}^{32}$ synthesis induces transcription from E. coli groE promoter, since the promoter is ${\sigma}^{32}-regulated$. When the strain was stressed with ethanol, phenol, and sodium chloride, clear inductions of ${\beta}-galactosidase$ were observed. Two types of simultaneous stresses of sodium chloride and phenol induced the enze much more than either of the two alone, suggesting that stress was an additive. The combined stress resulted in the highest induction of the enzyme in this system. The groE-lacZ fusion strain developed in this study can conveniently be used to detect other harmful pollutants in the environment. Stress treatment of cells containing recombinant proteins, which need GroEl, by ethanol, phenol, or sodium chloride, might have a tendency to increase their biological activities.

• Korean Journal of Microbiology
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• v.31 no.3
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• pp.189-196
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• 1993

Nucleotide sequences of nodD and nodA from Bradyrhizobium sp. SNUOOI were determined. The open reading frame (ORF) of nodD was 942 bp in length and encoded 314 amino acids. while ORF of nodA, sequence of which is the first one among legume symbionts Bradyrhizobium, was 630 bp and encoded 210 amino acids. The nucleotide sequence of nodD showed 99.4% homology with nodDI of B. japonicum USDAllO. while that of nodA showed 81.5% with B. sp. (Parasponial. At the 5' of nodYAB operon and nodD, consensus nod box sequences composed of 9 bp unit repeated four times and two times respectively were found. Also an A.T-rich sequence was found at 5' of nodD.