Journal of Microbiology

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Influences of genetically perturbing synthesis of the typical yellow pigment on conidiation, cell wall integrity, stress tolerance, and cellulase production in Trichoderma reesei: Weixin Zhang , Ning An , Junqi Guo , Zhixing Wang , Xiangfeng Meng , Weifeng Liu; J. Microbiol. 2021;59(4):426-434. Published online January 26, 2021; DOI: https://doi.org/10.1007/s12275-021-0433-0

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The prominent protein producing workhorse Trichoderma reesei secretes a typical yellow pigment that is synthesized by a gene cluster including two polyketide synthase encoding genes sor1 and sor2. Two transcription factors (YPR1 and YPR2) that are encoded in the same cluster have been shown to regulate the expression of the sor genes. However, the physiological relevance of the yellow pigment synthesis in T. reesei is not completely clear. In this study, a yellow pigment hyper-producer OEypr1 and three yellow pigment non-producers, OEypr1-sor1, Δypr1, and OEypr2, were constructed. Their phenotypic features in mycelial growth, conidiation, cell wall integrity, stress tolerance, and cellulase production were determined. Whereas hyperproduction of the yellow pigment caused significant defects in all the physiological aspects tested, the non-producers showed similar colony growth, but improved conidiation, maintenance of cell wall integrity, and stress tolerance compared to the control strain. Moreover, in contrast to the severely compromised extracellular cellobiohydrolase production in the yellow pigment hyperproducer, loss of the yellow pigment hardly affected induced cellulase gene expression. Our results demonstrate that interfering with the yellow pigment synthesis constitutes an engineering strategy to endow T. reesei with preferred features for industrial application.

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Co-inoculation of Soybean Seedling with Trichoderma asperellum and Irpex laceratus Promotes the Absorption of Nitrogen and Phosphorus
Zengyuan Tian, Xiaomin Wang, Yanyi Li, Yu Xi, Mengting He, Yuqi Guo
Current Microbiology.2024;[Epub] CrossRef
Small GTPase Rab7 is involved in stress adaptation to carbon starvation to ensure the induced cellulase biosynthesis in Trichoderma reesei
Lin Liu, Zhixing Wang, Yu Fang, Renfei Yang, Yi Pu, Xiangfeng Meng, Weifeng Liu
Biotechnology for Biofuels and Bioproducts.2024;[Epub] CrossRef
TrLys9 participates in fungal development and lysine biosynthesis in Trichoderma reesei
Jinling Lan, Lin Zhang, Jie Gao, Ronglin He
The Journal of General and Applied Microbiology.2023; 69(3): 159. CrossRef
MAPkinases regulate secondary metabolism, sexual development and light dependent cellulase regulation in Trichoderma reesei
Miriam Schalamun, Sabrina Beier, Wolfgang Hinterdobler, Nicole Wanko, Johann Schinnerl, Lothar Brecker, Dorothea Elisa Engl, Monika Schmoll
Scientific Reports.2023;[Epub] CrossRef
C-terminus of serine–arginine protein kinase-like protein, SrpkF, is involved in conidiophore formation and hyphal growth under salt stress in Aspergillus aculeatus
Natsumi Kobayashi, Ryohei Katayama, Kentaro Minamoto, Takashi Kawaguchi, Shuji Tani
International Microbiology.2023; 27(1): 91. CrossRef
Global regulation of fungal secondary metabolism in Trichoderma reesei by the transcription factor Ypr1, as revealed by transcriptome analysis
Jie Yang, Jia-Xiang Li, Fei Zhang, Xin-Qing Zhao
Engineering Microbiology.2023; 3(2): 100065. CrossRef
Dual Regulatory Role of Chromatin Remodeler ISW1 in Coordinating Cellulase and Secondary Metabolite Biosynthesis in Trichoderma reesei
Yanli Cao, Renfei Yang, Fanglin Zheng, Xiangfeng Meng, Weixin Zhang, Weifeng Liu, Xiaorong Lin
mBio.2022;[Epub] CrossRef
Heterologous Expression of Secondary Metabolite Genes in Trichoderma reesei for Waste Valorization
Mary L. Shenouda, Maria Ambilika, Elizabeth Skellam, Russell J. Cox
Journal of Fungi.2022; 8(4): 355. CrossRef
Morphologically favorable mutant of Trichoderma reesei for low viscosity cellulase production
Mukund G. Adsul, Pooja Dixit, Jitendra K. Saini, Ravi P. Gupta, Sankara Sri Venkata Ramakumar, Anshu S. Mathur
Biotechnology and Bioengineering.2022; 119(8): 2167. CrossRef
Identification of a Bidirectional Promoter from Trichoderma reesei and Its Application in Dual Gene Expression
Xiaoxiao Wu, Fuzhe Li, Renfei Yang, Xiangfeng Meng, Weixin Zhang, Weifeng Liu
Journal of Fungi.2022; 8(10): 1059. CrossRef
A histone H3K9 methyltransferase Dim5 mediates repression of sorbicillinoid biosynthesis in Trichoderma reesei
Lei Wang, Jialong Liu, Xiaotong Li, Xinxing Lyu, Zhizhen Liu, Hong Zhao, Xiangying Jiao, Weixin Zhang, Jun Xie, Weifeng Liu
Microbial Biotechnology.2022; 15(10): 2533. CrossRef
Transcriptome Comparison of Secondary Metabolite Biosynthesis Genes Expressed in Cultured and Lichenized Conditions of Cladonia rangiferina
Natalia Sveshnikova, Michele D. Piercey-Normore
Diversity.2021; 13(11): 529. CrossRef
From induction to secretion: a complicated route for cellulase production in Trichoderma reesei
Su Yan, Yan Xu, Xiao-Wei Yu
Bioresources and Bioprocessing.2021;[Epub] CrossRef

Differential expression of the major catalase, KatA in the two wild type Pseudomonas aeruginosa strains, PAO1 and PA14: Bi-o Kim , In-Young Chung , You-Hee Cho; J. Microbiol. 2019;57(8):704-710. Published online June 11, 2019; DOI: https://doi.org/10.1007/s12275-019-9225-1

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Abstract

KatA is the major catalase required for hydrogen peroxide (H2O2) resistance and acute virulence in Pseudomonas aeruginosa PA14, whose transcription is governed by its dual promoters (katAp1 and katAp2). Here, we observed that KatA was not required for acute virulence in another wild type P. aeruginosa strain, PAO1, but that PAO1 exhibited higher KatA expression than PA14 did. This was in a good agreement with the observation that PAO1 was more resistant than PA14 to H2O2 as well as to the antibiotic peptide, polymyxin B (PMB), supposed to involve reactive oxygen species (ROS) for its antibacterial activity. The higher KatA expression in PAO1 than in PA14 was attributed to both katAp1 and katAp2 transcripts, as assessed by S1 nuclease mapping. In addition, it was confirmed that the PMB resistance is attributed to both katAp1 and katAp2 in a complementary manner in PA14 and PAO1, by exploiting the promoter mutants for each -10 box (p1m, p2m, and p1p2m). These results provide an evidence that the two widely used P. aeruginosa strains display different virulence mechanisms associated with OxyR and Anr, which need to be further characterized for better understanding of the critical virulence pathways that may differ in various P. aeruginosa strains.

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Enhancing the compost maturation of deer manure and corn straw by supplementation via black liquor
Shijun Pan, Gang Wang, Yide Fan, Xiqing Wang, Juan Liu, Mingzhu Guo, Huan Chen, Sitong Zhang, Guang Chen
Heliyon.2023; 9(2): e13246. CrossRef
The small RNA PrrH of Pseudomonas aeruginosa regulates hemolysis and oxidative resistance in bloodstream infection
Shenghe Zeng, Qixuan Shi, YinZhen Liu, Mo Li, Dongling Lin, Shebin Zhang, Qiwei Li, Jieying Pu, Cong Shen, Bin Huang, Cha Chen, Jianming Zeng
Microbial Pathogenesis.2023; 180: 106124. CrossRef
Eco-evolutionary dynamics of experimental Pseudomonas aeruginosa populations under oxidative stress
Taoran Fu, Danna R. Gifford, Christopher G. Knight, Michael A. Brockhurst
Microbiology .2023;[Epub] CrossRef
The Pseudomonas aeruginosa DksA1 protein is involved in H2O2 tolerance and within-macrophages survival and can be replaced by DksA2
Alessandra Fortuna, Diletta Collalto, Veronica Schiaffi, Valentina Pastore, Paolo Visca, Fiorentina Ascenzioni, Giordano Rampioni, Livia Leoni
Scientific Reports.2022;[Epub] CrossRef
The role of dctP gene in regulating colonization, adhesion and pathogenicity of Vibrio alginolyticus strain HY9901
Yilin Zhang, Huimin Tan, Shiping Yang, Yucong Huang, Shuanghu Cai, Jichang Jian, Jia Cai, Qiwei Qin
Journal of Fish Diseases.2022; 45(3): 421. CrossRef
Nitrite Promotes ROS Production to Potentiate Cefoperazone-Sulbactam-Mediated Elimination to Lab-Evolved and Clinical-Evolved Pseudomonas aeruginosa
Su-fang Kuang, Xia Li, Ding-Yun Feng, Wen-Bin Wu, Hui Li, Bo Peng, Xuan-xian Peng, Zhuang-gui Chen, Tian-tuo Zhang, Adriana E. Rosato
Microbiology Spectrum.2022;[Epub] CrossRef
Nitrate Respiration Promotes Polymyxin B Resistance in Pseudomonas aeruginosa
Bi-o Kim, Hye-Jeong Jang, In-Young Chung, Hee-Won Bae, Eun Sook Kim, You-Hee Cho
Antioxidants & Redox Signaling.2021; 34(6): 442. CrossRef
The Bactericidal Tandem Drug, AB569: How to Eradicate Antibiotic-Resistant Biofilm Pseudomonas aeruginosa in Multiple Disease Settings Including Cystic Fibrosis, Burns/Wounds and Urinary Tract Infections
Daniel J. Hassett, Rhett A. Kovall, Michael J. Schurr, Nalinikanth Kotagiri, Harshita Kumari, Latha Satish
Frontiers in Microbiology.2021;[Epub] CrossRef
An antipathogenic compound that targets the OxyR peroxide sensor in Pseudomonas aeruginosa
Hyo-Young Oh, Shivakumar S. Jalde, In-Young Chung, Yeon-Ji Yoo, Hye-Jeong Jang, Hyun-Kyung Choi, You-Hee Cho
Journal of Medical Microbiology .2021;[Epub] CrossRef

PprM is necessary for up-regulation of katE1, encoding the major catalase of Deinococcus radiodurans, under unstressed culture conditions: Sun-Wook Jeong , Ho Seong Seo , Min-Kyu Kim , Jong-Il Choi , Heon-Man Lim , Sangyong Lim; J. Microbiol. 2016;54(6):426-431. Published online May 27, 2016; DOI: https://doi.org/10.1007/s12275-016-6175-8

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Abstract

Deinococcus radiodurans is a poly-extremophilic organism, capable of tolerating a wide variety of different stresses, such as gamma/ultraviolet radiation, desiccation, and oxidative stress. PprM, a cold shock protein homolog, is involved in the radiation resistance of D. radiodurans, but its role in the oxidative stress response has not been investigated. In this study, we investigated the effect of pprM mutation on catalase gene expression. pprM disruption decreased the mRNA and protein levels of KatE1, which is the major catalase in D. radiodurans, under normal culture conditions. A pprM mutant strain (pprMMT) exhibited decreased catalase activity, and its resistance to hydrogen peroxide (H2O2) decreased accordingly compared with that of the wild-type strain. We confirmed that RecG helicase negatively regulates katE1 under normal culture conditions. Among katE1 transcriptional regulators, the positive regulator drRRA was not altered in pprM-, while the negative regulators perR, dtxR, and recG were activated more than 2.5-fold in pprMMT. These findings suggest that PprM is necessary for KatE1 production under normal culture conditions by down-regulation of katE1 negative regulators.

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Antioxidant defense of Deinococcus radiodurans : how does it contribute to extreme radiation resistance?
Izabela Sadowska-Bartosz, Grzegorz Bartosz
International Journal of Radiation Biology.2023; 99(12): 1803. CrossRef
Development and Regulation of the Extreme Biofilm Formation of Deinococcus radiodurans R1 under Extreme Environmental Conditions
Qiannan Guo, Yuhua Zhan, Wei Zhang, Jin Wang, Yongliang Yan, Wenxiu Wang, Min Lin
International Journal of Molecular Sciences.2023; 25(1): 421. CrossRef
A small RNA regulates pprM, a modulator of pleiotropic proteins promoting DNA repair, in Deinococcus radiodurans under ionizing radiation
Jordan K. Villa, Runhua Han, Chen-Hsun Tsai, Angela Chen, Philip Sweet, Gabriela Franco, Respina Vaezian, Rok Tkavc, Michael J. Daly, Lydia M. Contreras
Scientific Reports.2021;[Epub] CrossRef
Lack of the Bacterial Phytochrome Protein Decreases Deinococcus radiodurans Resistance to Mitomycin C
Jong-Hyun Jung, Soyoung Jeong, Seonghun Im, Min-Kyu Kim, Ho Seong Seo, Sangyong Lim
Frontiers in Microbiology.2021;[Epub] CrossRef
Effects of Conserved Wedge Domain Residues on DNA Binding Activity of Deinococcus radiodurans RecG Helicase
Sun-Wook Jeong, Min-Kyu Kim, Lei Zhao, Seul-Ki Yang, Jong-Hyun Jung, Heon-Man Lim, Sangyong Lim
Frontiers in Genetics.2021;[Epub] CrossRef
The Novel ncRNA OsiR Positively Regulates Expression of katE2 and is Required for Oxidative Stress Tolerance in Deinococcus radiodurans
Lihua Gao, Xiaonan Chen, Ye Tian, Yongliang Yan, Yuhua Zhan, Zhengfu Zhou, Wei Zhang, Min Lin, Ming Chen
International Journal of Molecular Sciences.2020; 21(9): 3200. CrossRef
Conservation and diversity of radiation and oxidative stress resistance mechanisms inDeinococcusspecies
Sangyong Lim, Jong-Hyun Jung, Laurence Blanchard, Arjan de Groot
FEMS Microbiology Reviews.2019; 43(1): 19. CrossRef
Gene regulation for the extreme resistance to ionizing radiation of Deinococcus radiodurans
Wuzhou Wang, Yun Ma, Junyan He, Huizhou Qi, Fangzhu Xiao, Shuya He
Gene.2019; 715: 144008. CrossRef
PprM, a Cold Shock Domain-Containing Protein from Deinococcus radiodurans, Confers Oxidative Stress Tolerance to Escherichia coli
Sun-Ha Park, Harinder Singh, Deepti Appukuttan, Sunwook Jeong, Yong Jun Choi, Jong-Hyun Jung, Issay Narumi, Sangyong Lim
Frontiers in Microbiology.2017;[Epub] CrossRef
Knockout of pprM Decreases Resistance to Desiccation and Oxidation in Deinococcus radiodurans
Yang Zeng, Yun Ma, Fangzhu Xiao, Wuzhou Wang, Shuya He
Indian Journal of Microbiology.2017; 57(3): 316. CrossRef
RNA-Binding Domain is Necessary for PprM Function in Response to the Extreme Environmental Stress in Deinococcus radiodurans
Wei Li, Yun Ma, Jie Yang, Fangzhu Xiao, Wuzhou Wang, Shuya He
Indian Journal of Microbiology.2017; 57(4): 492. CrossRef

Purification and Characterization of a Catalase from Photosynthetic Bacterium Rhodospirillum rubrum S1 Grown under Anaerobic Conditions: Yoon-Suk Kang , Dong-Heon Lee , Byoung-Jun Yoon , Duck-Chul Oh; J. Microbiol. 2006;44(2):185-191.; DOI: https://doi.org/2366 [pii]

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Abstract: The photosynthetic bacterium, Rhodospirillum rubrum S1, when grown under anaerobic conditions, generated three different types of catalases. In this study, we purified and characterized the highest molecular weight catalase from the three catalases. The total specific catalase activity of the crude cell extracts was 88 U/mg. After the completion of the final purification step, the specific activity of the purified catalase was 1,256 U/mg. The purified catalase evidenced an estimated molecular mass of 318 kDa, consisting of four identical subunits, each of 79 kDa. The purified enzyme exhibited an apparent Km value of 30.4 mM and a Vmax of 2,564 U against hydrogen peroxide. The enzyme also exhibited a broad optimal pH (5.0~9.0), and remained stable over a broad temperature range (20°C~60°C). It maintained 90% activity against organic solvents (ethanol/chloroform) known hydroperoxidase inhibitors, and exhibited no detectable peroxidase activity. The catalase activity of the purified enzyme was reduced to 19% of full activity as the result of the administration of 10 mM 3-amino-1,2,4-triazole, a heme-containing catalase inhibitor. Sodium cyanide, sodium azide, and hydroxylamine, all of which are known heme protein inhibitors, inhibited catalase activity by 50% at concentrations of 11.5 μM, 0.52 μM, and 0.11 μM, respectively. In accordance with these findings, the enzyme was identified as a type of monofunctional catalase.

Purification and Characterization of Catalase-3 of Deinococcus radiophilus: Lee, In Jeong , Lee, Young Nam; J. Microbiol. 1995;33(3):239-243.

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Abstract: Deinococcus radiophilus, an UV resistant bacterium seemed to contain three issoenzymes of catalase. Among them, the samllest and most abundant species in cell-free extract, catalase-3 which also exhibited peroxidase activity was purified to electrophoretic homogeneity (145-fold purification) by chromatographic procedures. Its molecular weight was 155 kDa composed of four 38 kDa subunits. The K_m value of catalase-3 for H₂O₂was approximately 0.5 mM. This enzyme showed a typical ferric heme spectrum with maximum absorption at 405 nm. Upon binding to cyanide, the 405 nm peak shifted to 420 nm. Catalase-3 was very sensitive to inhibitors of heme proteins, such as cyanide, azide and hydroxylamine. A ratio of A_405/A_28O was 0.5 Catalase-3 was active over a wide range of pH, between pH 7 and 10. The enzyme was rather heat-labile and partially sensitive to ethanol-chloroform treatment, but resistant to 3-amino-1, 2, 4-triazole. Catalase-3 of D. radiophilus, which is a bifunction catalatic peroxidatic enzyme seemed to share certain molecular properties with the typical catalase and the catalase-peroxidase along with its own unique features.

Growth on methanol of a carboxydobacterium, acinetobacter sp. strain JC1 DSM 3803: Ro, Young Tae , Seo, Jae Goo , Lee, Joo Hun , Kim, Dae Myung , Chung, In Kwon , Kim, Tae Ue , Kim, Young Min; J. Microbiol. 1997;35(1):30-39.

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Abstract: Acinetobacter sp. strain JC1 DSM 3803, a carboxydobacterium, was found to grow methylotrophically at the expense of methanol and methlamine, but not of methane, formaldehyde, formate, dimethylamine, or trimethylamine, as the sole source of carbon and energy. The doubling times of the bacterium growing on methanol (0.5% v/v) and methylamine (0.5% w/v) at 30℃ and pH 6.8 were 4.8 h and 5.7 h respectively. Cells grown on methanol, however, failed to show typical methanol dehydrogenase and oxidase activities. The cell was found to contain no c-type cytochromes. Cells grown on methanol exhibited higher catalase activity than those grown on pyruvate or glucose. The catalase present in the cells also exhibited peroxidase activity. The catalase activity, growth on methanol of the cell, and oxygen consumption by methanol-grown maldehyde dehydrogenase, formaldehyde reductase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase activities were detected from cells grown on methanol.

Increased Activities of SOD and Catalase on Aerobic Growth in Arcobacter nitrofigilis: Park, Young Bok , han, Yeong Hwan; J. Microbiol. 1997;35(3):239-240.

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Abstract: A free-living nitrogen fixing Arcobacter nitrofigilis exhibuted the typical characteristics of aerobic growth in which the maximal cell growth was shown under an ambient air atmospjere, whereas no cell growth was shown umder an anaerobic condition. When oxygen concentration was increased, the activities of SOD and catalase were increased. These suggest that the aerobic nature of A. nitrofigilis might be due to the increased levels of both enzymes that scavenge toxic forms of oxygen.

Subcellular Localization of Catalase Encoded by the ctt1^+ Gene in Schizosaccharomyces pombe: Sang-il Lee , Joon Lee , Jung-Hye Roe; J. Microbiol. 2000;38(3):156-159.

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Abstract: The ctt1^+ gene in Schizosaccharomyces pombe encodes a catalase responsible for H_2O_2 -resistance of this organism as judged by the H_2O_2 -sensitive phenotype of the ctt1[delta] mutant. In this study, we investigated the subcellular localization of the Ctt1 gene product. In wild type cells catalase activity was detected in the organelle fraction as well as in the cytosol. The ctt1[delta] mutant contained no catalase activity, indicating that both cytosolic and organellar catalases are the products of a single ctt1^+ gene. Western blot analysis revealed two catalase bands, both of which disappeared in the ctt1[delta] mutant. The major, faster-migrating band existed in the cytosol whereas the minor, slower-migrating band appeared to be located in organelles, most likely in peroxisomes. These results suggest that the ctt1^++ gene product targeted to the peroxisome is a modified form of the one in the cytosol.

Enzyme Activities Related to the Methanol Oxidation of Mycobacterium sp. strain JC1 DSM 3803: Youngtae Ro , Eungbin Kim , Youngmin Kim; J. Microbiol. 2000;38(4):209-217.

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Abstract: Mycobacterium sp. strain JC1 DSM 3803 grown in methanol showed no methanol dehydrogenase or oxidase activities found in most methylotrophic bacteria and yeasts, respectively. Even though the methanol-grown cells exhibited a little methanol-dependent oxidation by cytochrome c-dependent methanol dehydrogenase and alcohol dehydrogenase, they were not the key enzymes responsible for the methanol oxidation of the cells, in that the cells contained no c-type cytochrome and the methanol oxidizing activity from the partially purified alcohol dehydrogenase was too low, respectively. In substrate switching experiments, we found that only a catalase-peroxidase among the three types of catalase found in glucose-grown cells was highly expressed in the methanol-grown cells and that its activity was relatively high during the exponential growth phase in Mycobacterium sp. JC1. Therefore, we propose that catalase-peroxidase is an essential enzyme responsible for the methanol metabolism directly or indirectly in Mycobacterium sp. JC1.

Analysis of Catalases from Photosynthetic Bacterium Rhodospirillum rubrum S1: Hee-Kyoung Lim , Young-Mi Kim , Dong-Heon Lee , Hyung-Yeel Kahng , Duck-Chul Oh; J. Microbiol. 2001;39(3):168-176.

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Abstract: Five different types of catalases from photosynthetic bacterium Rhodospirillum rubrum S1 grown aerobically in the dark were found in this study, and designated Cat1 (350 kDa), Cat2 (323 kDa), Cat3 (266 kDa), Cat4 (246 kDa), and Cat5 (238 kDa). Analysis of native PAGE revealed that Cat2, Cat3, and Cat4 were also produced in the cells anaerobically grown in the light. It is notable that only Cat2 was expressed much more strongly in response to the anaerobic condition. Enzyme activity staining demonstrated that Cat3 and Cat4 had bifunctional catalase-peroxidase activities, while Cat1, Cat2, and Cat5 were typical monofunctional catalases. S1 cells grown aerobically in the presence of malate as the sole source of carbon exhibited an apparent catalase Km value of 10 mM and a Vmax of about 705 U/mg protein at late stationary growth phase. The catalase activity of S1 cells grown in the anaerobic environment exhibited a much lower Vmax of about 109 U/mg protein at late logarithmic growth phase. The catalytic activity was stable in the broad range of temperatures (30 C-60 C), and pH (6.0-10.0). R. rubrum S1 was much more resistant to H_2 O_2 in the stationary growth phase than in the exponential growth phase regardless of growth conditions. Cells of stationary growth phase treated with 15 mM H 2 O 2 for 1 h showed 3-fold higher catalase activities than the untreated cells. In addition, L-glutamate induced an 80-fold increase in total catalase activity of R. rubrum S1 compared with malic acid. Through fraction analyses of S1 cells, Cat2, Cat3, Cat4 and Cat5 were found in both cytoplasm and periplasm, while Cat1 was localized only in the cytoplasm.

Examination of the Antioxidant Potential of Pycnogenol under Conditions of Oxidative Stress in Escherichia coli Mutants Deficient in HP1 and Superoxide Dismutase Activities: Jeong A Youm , Young Gon Kim; J. Microbiol. 2003;41(1):28-33.

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Abstract: Pycnogenol (PYC) is believed to have potential as a therapeutic agent against free radical-mediated oxidative stress. It is important, therefore, to understand the interactions between PYC and cellular defenses against oxidative stress. Toward this end, we analyzed the survival rates on the gene expression responses of E. coli sod katG mutants to PYC after pre-treatment of PQ or H_2O_2-mediated stress under aerobic conditions. We identified SOD induced by PYC, but not HP1 in sod katG mutants. A striking result was the PYC induction of SOD with antioxidant property in single katG mutant cells, particularly MnSOD and CuZnSOD. These inductions were further increased with oxidative stress, while HP1 was not induced in these conditions. The effects of pycnogenol treatment on these cells depend in part on its concentration on the stress response. Protective effects of PYC exposure which affected gene expression in cells were consistent with cell survival rates. Our results demonstrate that pycnogenol may alter the stress response gene expression in a specific manner such as SoxRS because PYC induction of single mutant only worked under increased PQ stress. All together our data indicate that SOD activity is essential for the cellular defense against PQ-mediated oxidative stress, suggesting that PYC may not be effective as an antioxidant in only oxidative stress conditions. On the other hand, it was expected that PYC may play a role as a pro-oxidant and if it is available for use, it should be evaluated carefully.

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