• Journal of Microbiology
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• v.43 no.1
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• pp.49-53
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• 2005

Putative genes for a two-component signal transduction system (akbS and akbT) were detected near the alkylbenzene-degrading operon of Rhodococcus sp. DK17. Sequence analysis indicates that AkbS possesses potential ATP-binding and histidine autophosphorylation sites in the N- and C-terminal regions, respectively, and that AkbT has a typical response regulator domain. Mutant analysis combined with RT-PCR experiments further shows that AkbS is required to induce the expression of o-xylene dioxygenase in DK17.

• Journal of Microbiology and Biotechnology
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• v.29 no.8
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• pp.1299-1309
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• 2019

As an opportunistic bacterial pathogen, Pseudomonas aeruginosa PAO1 contains two phenazine-producing gene operons, phzA1B1C1D1E1F1G1 (phz1) and phzA2B2C2D2E2F2G2 (phz2), each of which is independently capable of encoding all enzymes for biosynthesizing phenazines, including phenazine-1-carboxylic acid and its derivatives. Other previous study reported that the RpoS-deficient mutant SS24 overproduced pyocyanin, a derivative of phenazine-1-carboxylic acid. However, it is not known how RpoS mediates the expression of two phz operons and regulates pyocyanin biosynthesis in detail. In this study, with deletion of the rpoS gene in the $PA{\Delta}phz1$ mutant and the $PA{\Delta}phz2$ mutant respectively, we demonstrated that RpoS exerted opposite regulatory roles on the expression of the phz1and phz2 operons. We also confirmed that the phz1 operon played a critical role and especially biosynthesized much more phenazines than the phz2 operon when the rpoS gene was knocked out in P. aeruginosa. By constructing the translational reporter fusion vector lasR'-'lacZ and the chromosomal fusion mutant $PA{\Delta}lasR::lacZ$, we verified that RpoS deficiency caused increased expression of lasR, a transcription regulator gene in a first quorum sensing system (las) that activates overexpression of the phz1 operon, suggesting that in the absence of RpoS, LasR might act as an intermediate in overproduction of phenazine biosynthesis mediated by the phz1 operon in P. aeruginosa.

• Journal of Life Science
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• v.25 no.2
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• pp.136-150
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• 2015

Pseudomonas syringae pathovar tabaci is a plant pathogenic bacterium that causes wildfire disease in tobacco plants. In P. syringae pv. tabaci, PsyI, a LuxI-type protein, acts as an AHL synthase, while primary and secondary sequence analysis of PsyR has revealed that it is a homolog of the LuxR-type transcriptional regulator that responds to AHL molecules. In this study, using phenotypic and genetic analyses in P. syringae pv. tabaci, we show the effect of PsyR protein as a quorum-sensing (QS) transcriptional regulator. Regulatory effects of PsyR on swarming motility and production of siderophores, tabtoxin, and N-acyl homoserine lactones were examined via phenotypic assays, and confirmed by quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR). Further qRT-PCR showed that PsyR regulates expression of these virulence genes in response to environmental signals. However, an upstream region of the gene was not bound with purified MBP-PsyR protein; rather, PsyR was only able to shift the upstream region of psyI. These results suggested that PsyR may be indirectly controlled via intermediate-regulatory systems and that auto-regulation by PsyR does not occur.

• BMB Reports
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• v.40 no.2
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• pp.156-162
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• 2007

Two lysis-defective but DNA synthesis non-defective temperature-sensitive (ts) mutants of mycobacteriophage L1, L1G23ts23 and L1G25ts889 were found to be defective also in phage-specific RNA synthesis in the late period of their growth at 42$^{\circ}C$each to the extent of 50% of that at 32$^{\circ}C$The double mutant, L1G23ts23G25ts889 showed the ts defect in phage RNA synthesis that was nearly additive of those shown individually by the two single-mutant parents. Both G23 and G25 were shown to start functioning sometimes between 30 and 45 min after infection but the former gene might be dispensable after 45 min, while the latter was not. Northern analysis also shows that at 42$^{\circ}C$>, L1G23ts23 affects RNA synthesis more strongly than L1G25ts889 from L1 DNA segments that serve as the template for late gene transcription. Among the 21 virion and 12 non-virion late proteins synthesized by L1, L1G23ts23 is defective in the synthesis of at least 9 virion and all of non-virion proteins at 42$^{\circ}C$>. In contrast, L1G25ts889 is completely defective in synthesis of all the 33 late proteins. Possible roles of G23 and G25 in the positive regulation of transcription of different sets of late genes of L1 have been discussed.

• Journal of Microbiology and Biotechnology
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• v.20 no.2
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• pp.415-424
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• 2010

The purpose of this study was to investigate the relationship between the global regulatory mechanism known as quorum sensing and expression of virulence factors in Escherichia coli O157:87. A nonpolar luxS deletion was introduced into the chromosome of strain CI03J, a human clinical isolate from South Korea, to create the ${\Delta}luxS$ mutant strain ML03J. Phenotypic characterization of wild-type and mutant strains demonstrated that ML03J had no obvious growth or metabolic defects on 0.2% glucose LB medium, produced a functionally defective flagellum, and could not utilize sorbose; the biological significance of sorbose utilization is unknown. Omics-based analysis revealed the involvement of LuxS in the transcriptional activation of several flagella/chemotaxisrelated genes (flhD; fliA, C, D, S, Z; and cheA, Y, Z), repression of glutamate-dependent acid resistance genes (gadAB), and expression of virulence factors including Shiga toxin, hemolysin, and SepD within the LEE pathogenicity island.

• Journal of Microbiology and Biotechnology
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• v.17 no.9
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• pp.1504-1512
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• 2007

The fpr gene, which encodes a ferredoxin-$NADP^+$ reductase, is known to participate in the reversible redox reactions between $NADP^+$/NADPH and electron carriers, such as ferredoxin or flavodoxin. The role of Fpr and its regulatory protein, FinR, in Pseudomonas putida KT2440 on the oxidative and osmotic stress responses has already been characterized [Lee at al. (2006). Biochem. Biophys. Res. Commun. 339, 1246-1254]. In the genome of P. putida KT2440, another Fpr homolog (FprB) has a 35.3% amino acid identity with Fpr. The fprB gene was cloned and expressed in Escherichia coli. The diaphorase activity assay was conducted using purified FprB to identify the function of FprB. In contrast to the fpr gene, the induction of fprB was not affected by oxidative stress agents, such as paraquat, menadione, $H_2O_2$, and t-butyl hydroperoxide. However, a higher level of fprB induction was observed under osmotic stress. Targeted disruption of fprB by homologous recombination resulted in a growth defect under high osmotic conditions. Recovery of oxidatively damaged aconitase activity was faster for the fprB mutant than for the fpr mutant, yet still slower than that for the wild type. Therefore, these data suggest that the catalytic function of FprB may have evolved to augment the function of Fpr in P. putida KT2440.

• The Korean Journal of Physiology and Pharmacology
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• v.5 no.5
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• pp.367-371
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• 2001

The chromosome 7-linked long QT syndrome (LQT2) is caused by mutations in the human ether-a- go-go-related gene (HERG) that encodes the rapidly activating delayed rectifier $K^+$ current, $I_{Kr},$ in cardiac myocytes. Different types of mutations have been identified in various locations of HERG channel. One of the mechanisms for the loss of normal channel function is due to membrane trafficking of channel protein. The decreased channel function in some deletion mutants appears to be due to loss of coupling with wild type HERG to form the functional channel as the tetramer. Most of missense mutants with few exceptions could interact with wild type HERG to form functional tetramer and caused dominant negative suppression with co-injection with wild type HERG showing variable effects on current amplitude, voltage dependence, and kinetics of activation and inactivation. Two missense mutants at pore regions of HERG found in Japanese LQT2 (A614V and V630L) showed accentuated inward rectification due to a negative shift in steady-state inactivation and fast inactivation. One mutation in S4 region (R534C) produced a negative shift in current activation, indicating the S4 serving as the voltage sensor and accelerated deactivation. The C-terminus mutation, S818L, could not express the current by mutant alone and did not show dominant negative suppression with co-injection of equal amount of wild type cRNA. Co-injection of excess amount of mutant with wild type produced dominant negative suppression with a shift in voltage dependent activation. Therefore, multiple mechanisms are involved in different mutations and functional abnormality in LQT2. Further characterization with the interactions between various mutants in HERG and the regulatory subunits of the channels (MiRP1 and minK) is to be clarified.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2004.06a
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• pp.258-265
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• 2004

Numerous genes of Escherichia coli have been shown to growth phase-dependent expression throughout growth. The global patterns of growth phase-dependent gene expression of E. coli throughout growth using oligonucleotide microarrays containing a nearly complete set of 4,289 annotated open reading frames. To determine the change of gene expression throughout growth, we compared RNAs taken from timecourses with common reference RNA, which is combined with equal amount of RNA pooled from each time point. The hierarchical clustering of the conditions in accordance with timecourse expression revealed that growth phases were clustered into four classes, consistent with known physiological growth status. We analyzed the differences of expression levels at genome level in both exponential and stationary growth phase cultures. Statistical analysis showed that 213 genes are shown to, growth phase-dependent expression. We also analyzed the expression of 256 known operons and 208 regulatory genes. To assess the global impact of RpoS, we identified 193 genes coregulated with rpoS and their expression levels were examined in the isogenic rpoS mutant. The results revealed that 99 of 193 were novel RpoS-dependent stationary phase-induced genes and the majority of those are functionally unknown. Our data provide that global changes and adjustments of gene expression are coordinately regulated by growth transition in E. coli.

• Journal of Life Science
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• v.19 no.7
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• pp.866-870
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• 2009

Fascin, a cytoskeleton actin binding protein, functions in cell adhesion and cell migration. Fascin is also known as a candidate biomarker for various cancers, however, regulatory mechanisms of fascin expression remains little understood. In this study, we found an abnormal bristle phenotype, which is similar to that of the Drosophila fascin mutant, in Drafmutant flies. Hence, we investigated whether fascin expression is regulated by Raf signaling. RT-PCR and Western blot analysis showed that Drosophila fascin expression was down-regulated in Draf mutant flies and the level was increased in larvae expressing the oncogenic form of Draf (Draf$^{got}$) under the GAL4-UAS system. Immunostaining analysis showed increased fascin in the hemocytes over-expressing Draf$^{got}$. Our results indicate that fascin expression is regulated by Raf signaling and suggest that Raf signaling may play an important role in the actin cytoskeleton-associated developmental process and tumor progression via regulation of fascin gene.

• Microbiology and Biotechnology Letters
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• v.16 no.6
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• pp.450-456
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• 1988

For optimal production of L-tryptophan using a regulatory mutant of Escherichia coli the relationship between product formation and acid production was investigated. Experimental results showed that the production level of L-tryptophan was lowered as the specific acid production rate increased. In order to reduce the amount of acid produced during the fermentation, a controlled fed-batch fermentation was employed. In this fed-batch process, the feed rate of the nutrient feed medium was controlled in relation to the oxygen level in the culture and thus the growth of the cells was regulated in such n way that the oxygen demand of the culture could not exceed the oxygen sup-ply. When E. coli cells were cultivated in a controlled fed-batch mode of tormentor operation, the specific acid production rate was significantly reduced and L-tryptophan production was increased as much as five times that obtained in a conventional fed-batch fermentation.