• 한국미생물·생명공학회지
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• 제38권3호
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• pp.273-277
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• 2010

운데실프로지닌과 스트래토루빈 B는 S. coelicolor가 생산하는 붉은색 항생물질이다. 이번 연구에서 이들 붉은색 항생제의 생산성과 pH shock 스트레스와의 상관관계를 연구 하였다. 운데실프로디지닌과 스트랩토루빈 B의 생합성은 고체 R2YE 배지에서 산성 pH shock에 의해 증가되었다. 최적 pH shock은 pH 4로 비교군과 비교하여 각각 1.6배 및 2배 운데실프로디진과 스트랩토루빈 B의 생산성이 증가되었다. 게다가, 산성 pH 4의 세포 추출물은 T. mentagrophytes 에 대한 주목할만한 저항 활성을 나타내었다. 그러나, 중성 및 염기성 pH shock에서는 이들 항생제의 생산성뿐만 아니라 항진균 활성 증가가 일어나지 않았다. 그러므로, 비록 산성 pH shock이 간단하고 쉬운 방법이지만, 이들 붉은색 항생물질과 다른 이차대사산물의 생산성 향상에는 매우 효과적인 접근방법일 것이다.

• Journal of Microbiology and Biotechnology
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• 제23권10호
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• pp.1454-1459
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• 2013

The changes in prodiginines productions caused by pH shock culture of Streptomyces coelicolor strains were estimated. In Streptomyces coelicolor M511, undecylprodiginine and streptorubin B productions increased 1.8-fold (37.22 mg/g) and 2.5-fold (18.61 mg/g), respectively, by pH shock (from 7.2 to 4.0). In contrast, this resulted in the significantly decreased prodigignines production in the redP deletion mutant SJM1; 3.7-fold for undecylprodiginine, 4.4-fold for streptorubin B, 5.2-fold for methylundecylprodiginine, and 6.4-fold for methyldodecylundecylprodiginine, respectively. RT-PCR analyses showed that, during pH shock, expression of redD, the transcription activator gene, was increased while the expression of fabH, the decarboxylative condensation enzyme gene in fatty acid biosynthesis, was decreased in both strains. The enhanced redD expression was in good accordance with the increased total prodiginines production of M511. However, for SJM1 mutant, the decrease of fabH expression occurred more strikingly, such that it became almost completely turned off during acidic pH shock culture. Therefore, a down-regulation of fabH was considered to be the cause of decreased amount of total prodiginines produced, although redD expression was high in SJM1 mutant.

• Journal of Microbiology and Biotechnology
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• 제18권5호
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• pp.897-900
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• 2008

Various sequences of pH change were applied in a batch bioreactor to investigate pH shock effects on geldanamycin production by Streptomyces hygroscopicus subsp. duamyceticus JCM4427. In the control culture where the pH was not controlled, the maximum geldanamycin concentration was 414 mg/l. With the pHS1 mode of pH shock, that is, an abrupt pH change from pH 6.5 to pH 5.0 and then being maintained at around pH 5.0 afterward, 768 mg/l of geldanamycin was produced. With pHS2, in which the pH was changed sequentially from pH 6.7 to pH 5.0 and then back to pH 6.0, 429 mg/l of geldanamycin was produced. With pHS3 having a sequential pH change from pH 6.0 to pH 4.0 and then back to pH 6.5 followed by the third pH shock to pH 5.5, no geldanamycin production was observed. Considering that the productivity with pHS1 was about two-fold of that of the control culture with no pH control, we concluded that a more sophisticated manipulation of pH would further promote geldanamycin production.

• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3405-3409
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• 2013

The activation of heat shock factor 1 (HSF1) can be induced by the changes in environmental pH, but the mechanism of HSF1 activation by acidification is not completely understood. This paper reports that a low pH (pH~6.0) can trigger human HSF1 activation. Considering the involvement of the imidazole group of histidine residues under acid pH stress, an in vitro EMSA experiment, Trp-fluorescence spectroscopy, and protein structural analysis showed that the residue, His83, is the essential for pH-dependent human HSF1-activation. To determine the roles of His83 in the HSF1-mediated stress response affecting the cellular acid resistance, mouse embryo fibroblasts with normal wild-type or mutant mouse HSF1 expression were preconditioned by heating or pH stress. The results suggest that His83 is essential for HSF1 activation or the HSF1-mediated transcription of heat shock proteins, in protecting cells from acid pH stress.

• Journal of Microbiology and Biotechnology
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• 제18권4호
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• pp.658-662
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• 2008

Effects of pH shock on the secretion system of S. coelicolor A3(2) have been investigated at a transcriptional level by using DNA microarrays. Actinorhodin secretion was observed to be highly enhanced when an acidic-pH shock was applied to surface grown cultures of S. coelicolor A3(2). In this culture, a gene of actVA-orf1 encoding a putative efflux pump or transporter protein for actinorhodin was strongly upregulated. A major number of efflux pumps for other metabolites and a major number of secretion proteins for protein secretion were also observed to be upregulated with pH shock. The secretion of actinorhodin was observed to be remarkably enhanced in liquid culture as well.

• Journal of Microbiology and Biotechnology
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• 제23권2호
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• pp.149-155
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• 2013

Heterologous expression of a putative $K^+/H^+$ antiporter of Streptomyces coelicolor A3(2) (designated as sha4) in E. coli and Streptomyces hygroscopicus JCM4427 showed enhanced tolerance to $K^+$ stress, acidic-pH shock, and/or geldanamycin production under $K^+$ stress. In a series of $K^+$ extrusion experiments with sha4-carrying E. coli deficient in the $K^+/H^+$ antiporter, a restoration of impaired $K^+$ extrusion activity was observed. Based on this, it was concluded that sha4 was a true $K^+/H^+$ antiporter. In different sets of experiments, the sha4-carrying E. coli showed significantly improved tolerances to $K^+$ stresses and acidic-pH shock, whereas sha4-carrying S. hygroscopicus showed an improvement in $K^+$ stress tolerance only. The sha4-carrying S. hygroscopicus showed much higher geldanamycin productivity than the control under $K^+$ stress condition. In another set of experiments with a production medium, the secretion of geldanamycin was also significantly enhanced by the expression of sha4.

• Journal of Microbiology and Biotechnology
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• 제21권9호
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• pp.979-987
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• 2011

Culture pH change has some important roles in signal transduction and secondary metabolism. We have already reported that acidic pH shock enhanced actinorhodin production in Streptomyces coelicolor. Among many potential governing factors on pH variation, the putative $Na^+/H^+$ antiporter (sha) genes in S. coelicolor have been investigated in this study to elucidate the association of the sha on pH variation and secondary metabolism. Through the transcriptional analysis and overexpression experiments on 8 sha genes, we observed that most of the sha expressions were promoted by pH shock, and in the opposite way the pH changes and actinorhodin production were enhanced by the overexpression of each sha. We also confirmed that sha8 especially has a main role in maintaining cell viability and pH homeostasis through $Na^+$ extrusion, in salt effect experiment under the alkaline medium condition by deleting sha8. Moreover, this gene was observed to have a function of pH recovery after pH variation such as the pH shock, being able to cause the sporulation. However, actinorhodin production was not induced by the only pH recovery. The sha8 gene could confer on the host cell the ability to recover pH to the neutral level after pH variation like a pH drop. Sporulation was closely associated with this pH recovery caused by the action of sha8, whereas actinorhodin production was not due to such pH variation patterns alone.

• Asian-Australasian Journal of Animal Sciences
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• 제16권11호
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• pp.1577-1582
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• 2003

This study was conducted to determine the effects of prophylactic supplementation of vitamin E and Se on oxidative damage and antioxidant status. Fifteen healthy male buffalo (Bubalus bubalis) calves between the age of 6 to12 months were divided into three groups of five animals each: Group I-control, group II-endotoxic shock group infused with lyophilized E coli endotoxin @ 5 ${\mu}g$/kg body wt, and group III-supplemented with vitamin E @ 250 mg and Se @ 7.5 mg, one month prior to induction of endotoxic shock. All the animals in group II and group III exhibited signs of endotoxic shock. When the endotoxic shock was induced, there was significant (p<0.05) increase in the circulating levels of malonyl dialdehyde MDA (an indicator of lipid peroxidation). In the supplemented group III the magnitude of formation of MDA was also less as compared to group II at every stage of study. There was significant (p<0.05) decrease in circulating levels of SOD, GSH-Px, Catalase and G-6-PD activity from the normal (0 h) value with passage of time. As a result of endotoxic shock, these values reached a lowest value, and then showed a tendency towards the 0 h value. Prophylactic supplementation with vitamin E and Se was successful in reducing the quantum of oxidative damage due to formation of free radicals because of endotoxic shock.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.547-548
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• 2010

• 한국산업융합학회 논문집
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• 제2권2호
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• pp.115-124
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• 1999

The interaction of weak normal shock wave with turbulent boundary layer in a supersonic nozzle was investigated experimentally by wall static pressure measurements and by schlieren optical observations. The lime-mean flow in the interaction region was classified into four patterns according to the ratio of the pressure $p_k$ at the first kink point in the pressure distribution of the interaction region to the pressure $p_1$ just upstream of the shock. It is shown for any flow pattern that the wall static pressure rise near the shock foot can be described by the "free interaction" which is defined by Chapman et al. The ratio of the triple point height $h_t$ of the bifurcated shock to the undisturbed boundary layer thickness ${\delta}_1$ upstream of the interaction increases with the upstream Mach number $M_1$, and for a fixed $M_1$, the normalized triple point height $h_t/{\delta}_1$ decreases with increasing ${\delta}_1/h$, where h is the duct half-height.