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      Field Sanitation and Foliar Application of Streptomyces padanus PMS-702 for the Control of Rice Sheath Blight

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          Abstract

          Rice sheath blight (ShB), caused by Rhizoctonia solani Kühn AG1-IA, is one of the destructive rice diseases worldwide. The aims of this study were to develop biocontrol strategies focusing on field sanitation and foliar application with a biocontrol agent for ShB management. Streptomyces padanus PMS-702 showed a great antagonistic activity against R. solani. Fungichromin produced by S. padanus PMS-702, at 3.07 mg/l inhibited 50% mycelial growth, caused leakage of cytoplasm, and inhibited the formation of infection structures of R. solani. Fungichromin could reach to 802 mg/l when S. padanus PMS-702 was cultured in MACC broth for 6 days. Addition of 0.5% S. padanus PMS-702 broth into soil decreased the survival rate of the pathogen compared to the control. Soil amended with 0.5% S. padanus broth and 0.5% tea seed pomace resulted in the death of R. solani mycelia in the infested rice straws, and the germination of sclerotia was inhibited 21 days after treatment. Greenhouse trials revealed that S. padanus cultured in soybean meal–glucose (SMGC-2) medium after mixing with different surfactants could enhance its efficacy for inhibiting the pathogen. Of six surfactants tested, the addition of 2% tea saponin was the most effective in suppressing the pathogen. S. padanus broth after being fermented in SMGC-2, mixed with 2% tea saponin, diluted 100 fold, and sprayed onto rice plants significantly reduced ShB disease severity. Thus, S. padanus PMS-702 is an effective biocontrol agent. The efficacy of S. padanus PMS-702 for disease control could be improved through formulation.

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          Antibiotics produced by Streptomyces

          Streptomyces is a genus of Gram-positive bacteria that grows in various environments, and its shape resembles filamentous fungi. The morphological differentiation of Streptomyces involves the formation of a layer of hyphae that can differentiate into a chain of spores. The most interesting property of Streptomyces is the ability to produce bioactive secondary metabolites, such as antifungals, antivirals, antitumorals, anti-hypertensives, immunosuppressants, and especially antibiotics. The production of most antibiotics is species specific, and these secondary metabolites are important for Streptomyces species in order to compete with other microorganisms that come in contact, even within the same genre. Despite the success of the discovery of antibiotics, and advances in the techniques of their production, infectious diseases still remain the second leading cause of death worldwide, and bacterial infections cause approximately 17 million deaths annually, affecting mainly children and the elderly. Self-medication and overuse of antibiotics is another important factor that contributes to resistance, reducing the lifetime of the antibiotic, thus causing the constant need for research and development of new antibiotics.
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            Apoptosis induced by environmental stresses and amphotericin B in Candida albicans.

            New antifungal agents are urgently required to combat life-threatening infections caused by opportunistic fungal pathogens like Candida albicans. The manipulation of endogenous fungal programmed cell death responses could provide a basis for future therapies. Here we assess the physiology of death in C. albicans in response to environmental stresses (acetic acid and hydrogen peroxide) and an antifungal agent (amphotericin B). Exposure of C. albicans to 40-60 mM acetic acid, 5-10 mM hydrogen peroxide, or 4-8 microg.ml-1 amphotericin B produced cellular changes reminiscent of mammalian apoptosis. Nonviable cells that excluded propidium iodide displayed the apoptotic marker phosphatidylserine (as shown by annexin-V-FITC labeling), were terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL)-positive (indicating nuclease-mediated double-strand DNA breakage), and produced reactive oxygen species. Ultrastructural changes in apoptotic cells included chromatin condensation and margination, separation of the nuclear envelope, and nuclear fragmentation. C. albicans cells treated at higher doses of these compounds showed cellular changes characteristic of necrosis. Necrotic cells displayed reduced TUNEL staining, a lack of surface phosphatidylserine, limited reactive oxygen species production, and an inability to exclude propidium iodide. Necrotic cells lacked defined nuclei and showed extensive intracellular vacuolization. Apoptosis in C. albicans was associated with an accumulation of cells in the G2/M phase of the cell cycle, and under some apoptosis-inducing conditions, significant proportions of yeast cells switched to hyphal growth before dying. This is a demonstration of apoptosis in a medically important fungal pathogen.
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              Strategies for Fermentation Medium Optimization: An In-Depth Review

              Optimization of production medium is required to maximize the metabolite yield. This can be achieved by using a wide range of techniques from classical “one-factor-at-a-time” to modern statistical and mathematical techniques, viz. artificial neural network (ANN), genetic algorithm (GA) etc. Every technique comes with its own advantages and disadvantages, and despite drawbacks some techniques are applied to obtain best results. Use of various optimization techniques in combination also provides the desirable results. In this article an attempt has been made to review the currently used media optimization techniques applied during fermentation process of metabolite production. Comparative analysis of the merits and demerits of various conventional as well as modern optimization techniques have been done and logical selection basis for the designing of fermentation medium has been given in the present review. Overall, this review will provide the rationale for the selection of suitable optimization technique for media designing employed during the fermentation process of metabolite production.
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                Author and article information

                Journal
                Plant Pathol J
                Plant Pathol J
                The Plant Pathology Journal
                Korean Society of Plant Pathology
                1598-2254
                2093-9280
                1 February 2021
                1 February 2021
                1 February 2021
                : 37
                : 1
                : 57-71
                Affiliations
                [1 ]Department of Plant Pathology, National Chung Hsing University, Taichung 40227, Taiwan
                [2 ]Innovation and Development Center of Sustainable Agriculture, National Chung Hsing University, Taichung 407, Taiwan
                Author notes
                [* ]Co-corresponding authors. T.-P. Huang, Phone) +886-4-22840780 (ext. 379), FAX) +886-4-22859750, E-mail) tphuang@ 123456nchu.edu.tw , J.-W. Huang, Phone) +886-4-22840780 (ext. 351), FAX) +886-4-22877585, E-mail) jwhuang@ 123456nchu.edu.tw , ORCID, Tzu-Pi Huang https://orcid.org/0000-0003-2904-3373, Jenn-Wen Huang https://orcid.org/0000-0003-0798-4332

                Handling Editor : Youn-Sig Kwak

                [¶]

                Current address: Sinon Corporation, Taichung 43251, Taiwan

                Article
                ppj-37-1-57
                10.5423/PPJ.OA.12.2020.0227
                7847755
                © The Korean Society of Plant Pathology

                This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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