• Microbiology and Biotechnology Letters
• /
• v.38 no.3
• /
• pp.273-277
• /
• 2010

Undecylprodiginine and streptorubin B are red-pigmented antibiotics produced by Streptomyces coelicolor A3(2). In this study, we investigated the correlation between productivity of these red-pigmented antibiotics and stress of pH shock. Biosynthesis of these red-pigmented antibiotics is enhanced at acidic pH shock on solid R2YE medium. The optimal pH shock is pH 4 which led to 1.6 fold and two-fold increase in the production of undecylprodiginine and streptorubin B as compared with control, respectively. In addition, the extract of pH 4 shocked cells exhibited a remarkable activity against Trichophyton mentagrophytes. However, neutral and basic pH shock did not give raise to promote a production of these red-pigmented antibiotics as well as antifungal activity. Thus, although the acidic pH shock is simple and easy method, it should be extremely effective approach to enhance a productivity of these red-pigmented antibiotics and other secondary metabolites.

• Journal of Microbiology and Biotechnology
• /
• v.23 no.10
• /
• pp.1454-1459
• /
• 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
• /
• v.23 no.2
• /
• pp.149-155
• /
• 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
• /
• v.18 no.4
• /
• pp.658-662
• /
• 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
• /
• v.21 no.9
• /
• pp.979-987
• /
• 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.

• Microbiology and Biotechnology Letters
• /
• v.35 no.1
• /
• pp.26-29
• /
• 2007

Tautomycetin (TMC), which is produced by Streptomyces sp. CK4412, is a novel activated T cell-specific immunosuppressive compound with an ester bond linkage between a terminal cyclic anhydride moiety and a linear polyketide chain bearing an unusual terminal alkene. Antifungal activity against Aspergillus niger and TMC productivity assayed by HPLC using culture extracts from Streptomyces sp. CK4412 grown on solid medium adjusted at various pH were measured. The cells cultured at acidic pH (pH 4-5) medium exhibited much stronger antifungal activity as well as higher TMC productivity than those cultured at neutral pH medium, implying that the acidic pH-shock should be an efficient strategy to induce the productivity of secondary metabolites in Streptomyces culture.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.53 no.5
• /
• pp.733-739
• /
• 2020

Olive flounder Paralichthys olivaceus (total weight 216.4±14.6 g, total length 28.4±1.7 cm) were exposed to different pH levels (3, 4, 5, 6, 7, 8, and 9) for 96 h. At pH 4, hemoglobin decreased significantly, while plasma calcium, glucose, cholesterol, and ALP increased significantly. Exposure to pH 4 also induced stress responses, as evidenced by a significant decrease in heat shock protein 70 (HSP 70) and a significant increase in cortisol. The results of this study indicate that acute exposure to acidic or alkaline pH (pH 3 or 9) induced significant mortality, while exposure to pH 4significantly affected hematological parameters and stress responses in P. olivaceus.

• Environmental Engineering Research
• /
• v.10 no.4
• /
• pp.181-190
• /
• 2005

Severe loss or hydrogen occurred in most anaerobic hydrogen fermentation reactors. Several selected methods were applied to suppress the consumption of hydrogen and increase the potential of production. As the first trial, pH shock was applied. The pH of reactor was dropped nearly to 3.0 by stopping alkalinity supply and on]y feeding glucose (5 g/L-d). As the pH was increase to $4.8{\pm}0.2,$ the degradation pathway was derived to solventogenesis resulting in disappearance of hydrogen in the headspace. In the aspect of bacterial community, methanogens weren't detected after 22 and 35 day, respectively. Even though, however, there was no methanogenic bacterium detected with fluorescence in-situ hybridization (FISH) method, hydrogen loss still occurred in the reactor showing a continuous increase of acetate when the pH was increased to $5.5{\pm}0.2$. This result was suggesting the possibility of the survival of spore fanning acetogenic bacteria enduring the severely acidic pH. As an alternative and additive method, nitrate was added in a batch experiment. It resulted in the increase of maximum hydrogen fraction from 29 (blank) to 61 % $(500\;mg\;NO_3/L)$. However, unfortunately, the loss of hydrogen occurred right after the depletion of nitrate by denitrification. In order to prevent the loss entangled with acetate formation, $CO_2$ scavenging in the headspace was applied to the hydrogen fermentation with heat-treated sludge since it was the primer of acetogenesis. As the $CO_2$ scavenging was applied, the maximum fraction of hydrogen was enhanced from 68 % to 87 %. And the loss of hydrogen could be protected effectively.

• Journal of Life Science
• /
• v.27 no.1
• /
• pp.15-22
• /
• 2017

Streptococcus mutans (S. mutans), which plays a major role in the etiology of human dental caries, is able to tolerate exposure to acid shock in addition to its acidogenicity. We investigated the effects of pH stress on membrane fluidity, activities and expression levels of F-ATPase, and proton permeability in S. mutans. Using 1,6-diphenyl-1,3,5-hexatriene, we observed membrane ordering at pH 4.8 and pH 8.8. The ordering effects were larger at pH 4.8 in cytoplasmic membranes isolated from S. mutans (CMSM). Increasing pH resulted in a decrease in the activities and expression levels of F-ATPase. The proton permeability was decreased at both acidic and alkaline pHs, and the lowest permeability was observed at pH 4.8. The lower permeability at pH 8.8 than pH 6.8 is likely to be caused by the decreased proton influx due to the decreased CMSM fluidity. In addition, it seems to be evident that extremely low permeability at pH 4.8 was caused by the decreased proton influx due to the decreased CMSM fluidity as well as the increased proton efflux due to the increased activity and expression level of F-ATPase. It is likely that CMSM fluidity and F-ATPase activity are two major key factors that determine proton permeability in S. mutans. We suggest that CMSM fluidity plays an important role in the determination of proton permeability, which sheds light on the possibility of using nonspecific membrane fluidizers, e.g., ethanol, for anti-caries purposes.

• Korean Journal of Ecology and Environment
• /
• v.35 no.3 s.99
• /
• pp.145-151
• /
• 2002

The effect of low pH on physiological changes was studied with the acidophilic green alga, Clamydomonas acidophila, UTCC 122. The growthrates (${\mu}$) were identical, $0.5{\sim}0.7\;day^{-1}$, at pH 3.7${\sim}$6.7 and no significantly different (ANOVA, p =0.134), showing cell volume reduced gradually as they were growing, whereas that at pH 2.7 was falling to zero and cell volume increased dramatically. Chlorophyll a concentration of the cultures incubated for one day was $191{\sim}255\;pg\;cell^{-1}$, after then it declined from $60{\sim}103\;pg\;cell^{-1}$ at pH 3.7${\sim}$6.7 except $210\;pg\;cell^{-1}$ at pH 2.7, which was directly related with cell volume. External carbonic anhydrase (CA) activity was varied from1.1 to$3.7{\times}10^{-4}\;E.U.\;mm^{-2}$, showing the gradualincrease during culture, except at 2.7 and pH 5.7. However there was not found any relationship among the pH gradient cultures. CA molecular mass of C. acidophila was 29 kBa, and concentration of that was identical in all cultures. The proteins of 41 kDa and 63 were not or very　faintly expressed in low pH cultures, in contrast that of 17 kDa more expressed. In this work, we found that C. acidophila could live optimally within a wide range of acidic pH, and 17 kDa of unidentified protein might be concerned with tolerating in low acid environment.