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Taghavi S, Abbasi Montazeri E, Zekavati R, Roomiani L, Saffarian P. Identification of a New Compound (4-Fluoro-2-Trifluoromethyl Imidazole) Extracted from a New Halophilic Bacillus aquimaris Strain Persiangulf TA2 Isolated from the Northern Persian Gulf with Broad-Spectrum Antimicrobial Effect. IRANIAN JOURNAL OF BIOTECHNOLOGY 2023; 21:e3359. [PMID: 38269196 PMCID: PMC10804065 DOI: 10.30498/ijb.2023.338788.3359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 05/18/2023] [Indexed: 01/26/2024]
Abstract
Background The unique ecosystem of the Persian Gulf has made it a rich source of natural antimicrobial compounds produced by various microorganisms, especially bacteria, which can be used in the treatment of infectious diseases, especially those of drug-resistant microbes. Objectives This study aimed to identify antimicrobial compounds in the bacteria isolated from the northern region of the Persian Gulf in Abadan (Chavibdeh port), Iran, for the first time. Materials and Methods Sampling was performed in the fall on November 15, 2019, from 10 different stations (water and sediment samples). The secondary metabolites of all isolates were extracted, and their antimicrobial effects were investigated. 16S ribosomal ribonucleic acid sequencing was used for the identification of the strains that showed the best inhibition against selected pathogens, and growth conditions were optimized for them. A fermentation medium in a volume of 5000 mL was prepared to produce the antimicrobial compound by the superior strain. The extracted antimicrobial compounds were identified using the gas chromatography-mass spectrometry technique. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined for the superior strain. The effects of salinity, pH, and temperature on the production of antimicrobial compounds were determined by measuring the inhibitory region (mm) of methicillin-resistant Staphylococcus aureus (MRSA). Results Four new strains with antimicrobial properties (i.e., Halomonas sp. strain Persiangulf TA1, Bacillus aquimaris strain Persiangulf TA2, Salinicoccus roseus strain Persiangulf TA4, and Exiguobacterium profundum strain Persiangulf TA9) were identified. The optimum growth temperatures were determined at 37-30, 37, and 40 °C for TA1 and TA2, TA4, and TA9 strains, respectively. The optimum pH values for the four strains were 7, 6-7, 7.5, and 6.5-7.5, respectively. The optimal salt concentrations for the four strains were 15%, 2.5-5%, 7.5%, and 5%, respectively. The ethyl acetate extract of strain Persiangulf TA2 showed extensive antimicrobial activity against human pathogens (75%) and MRSA. The most abundant compound identified in TA2 extract was the new compound 4-fluoro-2-trifluoromethyl imidazole. The MBC and MIC for the ethyl acetate extract of strain TA2 were 20 and 5 mg. mL-1 (Staphylococcus aureus), 40 and 20 mg. mL-1 (MRSA, Escherichia coli, and Enterococcus faecalis), 40 and 10 mg. mL-1 Acinetobacter baumannii), and 80 and 40 mg. mL-1 (Staphylococcus epidermidis, Shigella sp., Bacillus cereus, and Klebsiella pneumoniae), respectively. The optimal conditions for antibiotic production by TA2 strain were 5% salt concentration, pH of 7, and temperature of 35 °C. Conclusion Newly detected natural compounds in TA2 strain due to superior antimicrobial activity even against MRSA strain can be clinically valuable in pharmacy and treatment.
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Affiliation(s)
- Sara Taghavi
- Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
| | - Effat Abbasi Montazeri
- Department of Microbiology, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Roya Zekavati
- Department of Biology, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran
| | - laleh Roomiani
- Department of Fisheries, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran
| | - Parvaneh Saffarian
- Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
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Two new 22-membered macrolides from Streptomyces sp. HU210. J Antibiot (Tokyo) 2022; 75:650-653. [DOI: 10.1038/s41429-022-00563-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 08/20/2022] [Accepted: 09/01/2022] [Indexed: 11/08/2022]
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Davies-Bolorunduro O, Osuolale O, Saibu S, Adeleye I, Aminah N. Bioprospecting marine actinomycetes for antileishmanial drugs: current perspectives and future prospects. Heliyon 2021; 7:e07710. [PMID: 34409179 PMCID: PMC8361068 DOI: 10.1016/j.heliyon.2021.e07710] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 07/25/2021] [Accepted: 07/30/2021] [Indexed: 01/01/2023] Open
Abstract
Revived analysis interests in natural products in the hope of discovering new and novel antileishmanial drug leads have been driven partially by the increasing incidence of drug resistance. However, the search for novel chemotherapeutics to combat drug resistance had previously concentrated on the terrestrial environment. As a result, the marine environment was often overlooked. For example, actinomycetes are an immensely important group of bacteria for antibiotic production, producing two-thirds of the known antibiotics. However, these bacteria have been isolated primarily from terrestrial sources. Consequently, there have been revived efforts to discover new compounds from uncharted or uncommon environments like the marine ecosystem. Isolation, purification and structure elucidation of target compounds from complex metabolic extract are major challenges in natural products chemistry. As a result, marine-derived natural products from actinomycetes that have antileishmanial bioactivity potentials have been understudied. This review highlights metagenomic and bioassay approaches which could help streamline the drug discovery process thereby greatly reducing time and cost of dereplication to identify suitable antileishmanial drug candidates.
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Affiliation(s)
- O.F. Davies-Bolorunduro
- Microbiology Department, Nigerian Institute of Medical Research, Lagos, Nigeria
- Postdoc Fellow Department of Chemistry, Faculty of Science and Technology, Universitas Airlangga, Komplek Kampus C, Jl. Mulyorejo, Surabaya, 60115, Indonesia
| | - O. Osuolale
- Applied Environmental Metagenomics and Infectious Diseases Research Group (AEMIDR), Department of Biological Sciences, Elizade University, Ilara Mokin, Nigeria
| | - S. Saibu
- Department of Microbiology, University of Lagos, Akoka, Lagos, Nigeria
| | - I.A. Adeleye
- Department of Microbiology, University of Lagos, Akoka, Lagos, Nigeria
| | - N.S. Aminah
- Department of Chemistry, Faculty of Science and Technology, Universitas Airlangga, Komplek Kampus C UNAIR, Jl. Mulyorejo, Surabaya, 60115, Indonesia
- Biotechnology of Tropical Medicinal Plants Research Group, Universitas Airlangga, Indonesia
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Sun TT, Yang JK, Zhu HJ, Pan L, Cao F. Antibacterial Secondary Metabolites from the Marine-Derived Fungus Penicillium janthinellum. Chem Nat Compd 2020. [DOI: 10.1007/s10600-020-03204-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Nishimaru T, Eto K, Komine K, Ishihara J, Hatakeyama S. Total Synthesis of Lajollamycin B. Chemistry 2019; 25:7927-7934. [DOI: 10.1002/chem.201901069] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Indexed: 11/12/2022]
Affiliation(s)
- Tatsuya Nishimaru
- Graduate School of Biomedical SciencesNagasaki University, Bunkyo-machi Nagasaki 8 52-8521 Japan
| | - Kohei Eto
- Graduate School of Biomedical SciencesNagasaki University, Bunkyo-machi Nagasaki 8 52-8521 Japan
| | - Keita Komine
- Graduate School of Biomedical SciencesNagasaki University, Bunkyo-machi Nagasaki 8 52-8521 Japan
| | - Jun Ishihara
- Graduate School of Biomedical SciencesNagasaki University, Bunkyo-machi Nagasaki 8 52-8521 Japan
| | - Susumi Hatakeyama
- Medical Innovation CenterNagasaki University, Bunkyo-machi Nagasaki 852-8521 Japan
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Maciel OMC, Tavares RSN, Caluz DRE, Gaspar LR, Debonsi HM. Photoprotective potential of metabolites isolated from algae-associated fungi Annulohypoxylon stygium. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2017; 178:316-322. [PMID: 29175758 DOI: 10.1016/j.jphotobiol.2017.11.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 10/31/2017] [Accepted: 11/12/2017] [Indexed: 11/28/2022]
Abstract
Natural products, or secondary metabolites, obtained from fungal species associated with marine algae have been widely used in sunscreens due to their antioxidant activity and protective potential against solar radiation. The endophytic fungus isolated from Bostrychia radicans algae collected in the Rio Escuro mangrove, São Paulo State, Brazil, Annulohypoxylon stygium (Xylariaceae family) was studied to evaluate the photoprotective potential of its metabolites. The Annulohypoxylon genus can produce secondary metabolites with interesting cytotoxic, antibacterial and antioxidant properties and was never isolated before from a marine alga or had its metabolites studied for UV protection. The fungal culture (code As) extracted with dichloromethane: methanol (2:1) yielded 9 fractions (Asa to Asi) which were submitted to different chromatographic methodologies to obtain pure compounds, and to spectroscopic methodologies to elucidate their structures. Also, a screening was conducted to evaluate the qualitative production of the metabolites, besides the absorption in the UVA/UVB range, their photostability and phototoxicity potential using the 3T3 NRU phototoxicity test (OECD TG 432). This study led to the isolation of a novel compound, 3-benzylidene-2-methylhexahydropyrrolo [1,2-α] pyrazine-1,4-dione (1), from fractions Ase3 and Asf3; Ase1 was identified as 1-(1,3-Benzodioxol-5-yl)-1,2-propanediol (2), two metabolites were isolated as diastereomers (1S,2R)-1-phenyl-1,2-propanediol (3) from Asd2 and (1R,2R)-1-phenyl-1,2-propanediol (4) from Asd3, and Ase1 and 1,3-benzodioxole-5-methanol (5) from Asc1. The results obtained showed a great potential source of new molecules to be used as UVB filters in sunscreens, since substances 1-2 presented UVB absorption, had no phototoxic potential and were considered photostable. In conclusion, these compounds can be considered as a potential new class of molecules for photoprotection, since their photosafety and non-cytotoxicity were predicted using in vitro methods for topical use. Meanwhile, further efficacy assays shall be conducted for the establishment of their Sun Protection Factor (SPF). Also, this work provided new information concerning the metabolic profile of A. stygium, since it was possible to obtain two enantiomer compounds (3) and (4). One of them belonged to the same skeleton, but with a methylenedioxy moiety, showing the richest enzymatic pattern for this microorganism.
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Affiliation(s)
- Olívia Maria Campanini Maciel
- Department of Physics and Chemistry, School of Pharmaceutical Sciences of Ribeirão Preto - University of Sao Paulo, Ribeirao Preto, Brazil
| | - Renata Spagolla Napoleão Tavares
- Department of Pharmaceutical Sciences, School of Pharmaceutical Sciences of Ribeirão Preto - University of Sao Paulo, Ribeirao Preto, Brazil
| | - Daniela Ricardo Engracia Caluz
- Department of Physics and Chemistry, School of Pharmaceutical Sciences of Ribeirão Preto - University of Sao Paulo, Ribeirao Preto, Brazil
| | - Lorena Rigo Gaspar
- Department of Pharmaceutical Sciences, School of Pharmaceutical Sciences of Ribeirão Preto - University of Sao Paulo, Ribeirao Preto, Brazil
| | - Hosana Maria Debonsi
- Department of Physics and Chemistry, School of Pharmaceutical Sciences of Ribeirão Preto - University of Sao Paulo, Ribeirao Preto, Brazil.
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Marine natural products with anti-inflammatory activity. Appl Microbiol Biotechnol 2015; 100:1645-1666. [DOI: 10.1007/s00253-015-7244-3] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 12/07/2015] [Accepted: 12/09/2015] [Indexed: 12/14/2022]
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Yin M, Liu D, Xu F, Xiao L, Wang Q, Wang B, Chang Y, Zheng J, Tao X, Liu G, Zhang L. A specific antimicrobial protein CAP-1 from Pseudomonas sp. isolated from the jellyfish Cyanea capillata. Int J Biol Macromol 2015; 82:488-96. [PMID: 26529191 DOI: 10.1016/j.ijbiomac.2015.10.056] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 10/16/2015] [Accepted: 10/19/2015] [Indexed: 12/22/2022]
Abstract
A bacterium strain, designated as CMF-2, was isolated from the jellyfish Cyanea capillata and its culture supernatant exhibited a significant antimicrobial activity. The strain CMF-2 was identified as Pseudomonas sp. based on the morphological, biochemical and physiological characteristics as well as 16S rRNA sequence analysis. In this study, an antimicrobial protein, named as CAP-1, was isolated from the culture of CMF-2 through ammonium sulfate precipitation and gel filtration chromatography. According to the result of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), a major band indicated that the antimicrobial protein had a molecular mass of about 15 kDa, and it was identified as a hypothetical protein by MALDI-TOF-MS analysis and Mascot searching. CAP-1 displayed a broad antimicrobial spectrum against the indicator bacteria and fungus, including Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Candida albicans, especially some marine-derived microorganisms such as Vibrio vulnificus, Vibrio alginolyticus, Vibrio parahaemolyticus, Vibrio cholera, and Vibrio anguillarum, but showed little impact on tumor cells and normal human cells. The protein CAP-1 remained a stable antimicrobial activity in a wide range of temperature (20-80°C) and pH (2-10) conditions. These results suggested that CAP-1 might have a specific antimicrobial function not due to cytotoxicity.
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Affiliation(s)
- Manman Yin
- Marine Bio-pharmaceutical Institute, Second Military Medical University, Shanghai 200433, China; Department of Marine Biotechnology, Faculty of Naval Medicine, Second Military Medical University, Shanghai 200433, China.
| | - Dan Liu
- Marine Bio-pharmaceutical Institute, Second Military Medical University, Shanghai 200433, China; Department of Marine Biotechnology, Faculty of Naval Medicine, Second Military Medical University, Shanghai 200433, China.
| | - Feng Xu
- Department of Food Microbiology, College of Food Science and Engineering, Dalian Ocean University, Dalian 116021, China.
| | - Liang Xiao
- Marine Bio-pharmaceutical Institute, Second Military Medical University, Shanghai 200433, China; Department of Marine Biotechnology, Faculty of Naval Medicine, Second Military Medical University, Shanghai 200433, China.
| | - Qianqian Wang
- Marine Bio-pharmaceutical Institute, Second Military Medical University, Shanghai 200433, China; Department of Marine Biotechnology, Faculty of Naval Medicine, Second Military Medical University, Shanghai 200433, China.
| | - Beilei Wang
- Marine Bio-pharmaceutical Institute, Second Military Medical University, Shanghai 200433, China; Department of Marine Biotechnology, Faculty of Naval Medicine, Second Military Medical University, Shanghai 200433, China.
| | - Yinlong Chang
- Marine Bio-pharmaceutical Institute, Second Military Medical University, Shanghai 200433, China.
| | - Jiemin Zheng
- Marine Bio-pharmaceutical Institute, Second Military Medical University, Shanghai 200433, China; Department of Marine Biotechnology, Faculty of Naval Medicine, Second Military Medical University, Shanghai 200433, China.
| | - Xia Tao
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai 200003, China
| | - Guoyan Liu
- Marine Bio-pharmaceutical Institute, Second Military Medical University, Shanghai 200433, China; Department of Marine Biotechnology, Faculty of Naval Medicine, Second Military Medical University, Shanghai 200433, China.
| | - Liming Zhang
- Marine Bio-pharmaceutical Institute, Second Military Medical University, Shanghai 200433, China; Department of Marine Biotechnology, Faculty of Naval Medicine, Second Military Medical University, Shanghai 200433, China.
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Mining microbial metatranscriptomes for expression of antibiotic resistance genes under natural conditions. Sci Rep 2015; 5:11981. [PMID: 26153129 PMCID: PMC4495384 DOI: 10.1038/srep11981] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 06/15/2015] [Indexed: 11/08/2022] Open
Abstract
Antibiotic resistance genes are found in a broad range of ecological niches associated with complex microbiota. Here we investigated if resistance genes are not only present, but also transcribed under natural conditions. Furthermore, we examined the potential for antibiotic production by assessing the expression of associated secondary metabolite biosynthesis gene clusters. Metatranscriptome datasets from intestinal microbiota of four human adults, one human infant, 15 mice and six pigs, of which only the latter have received antibiotics prior to the study, as well as from sea bacterioplankton, a marine sponge, forest soil and sub-seafloor sediment, were investigated. We found that resistance genes are expressed in all studied ecological niches, albeit with niche-specific differences in relative expression levels and diversity of transcripts. For example, in mice and human infant microbiota predominantly tetracycline resistance genes were expressed while in human adult microbiota the spectrum of expressed genes was more diverse, and also included β-lactam, aminoglycoside and macrolide resistance genes. Resistance gene expression could result from the presence of natural antibiotics in the environment, although we could not link it to expression of corresponding secondary metabolites biosynthesis clusters. Alternatively, resistance gene expression could be constitutive, or these genes serve alternative roles besides antibiotic resistance.
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10
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Antibacterial products of marine organisms. Appl Microbiol Biotechnol 2015; 99:4145-73. [PMID: 25874533 DOI: 10.1007/s00253-015-6553-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Revised: 03/17/2015] [Accepted: 03/19/2015] [Indexed: 10/23/2022]
Abstract
Marine organisms comprising microbes, plants, invertebrates, and vertebrates elaborate an impressive array of structurally diverse antimicrobial products ranging from small cyclic compounds to macromolecules such as proteins. Some of these biomolecules originate directly from marine animals while others arise from microbes associated with the animals. It is noteworthy that some of the biomolecules referred to above are structurally unique while others belong to known classes of compounds, peptides, and proteins. Some of the antibacterial agents are more active against Gram-positive bacteria while others have higher effectiveness on Gram-negative bacteria. Some are efficacious against both Gram-positive and Gram-negative bacteria and against drug-resistant strains as well. The mechanism of antibacterial action of a large number of the chemically identified antibacterial agents, possible synergism with currently used antibiotics, and the issue of possible toxicity on mammalian cells and tissues await elucidation. The structural characteristics pivotal to antibacterial activity have been ascertained in only a few studies. Demonstration of efficacy of the antibacterial agents in animal models of bacterial infection is highly desirable. Structural characterization of the active principles present in aqueous and organic extracts of marine organisms with reportedly antibacterial activity would be desirable.
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Harvey AL, Edrada-Ebel R, Quinn RJ. The re-emergence of natural products for drug discovery in the genomics era. Nat Rev Drug Discov 2015; 14:111-29. [PMID: 25614221 DOI: 10.1038/nrd4510] [Citation(s) in RCA: 1497] [Impact Index Per Article: 166.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Natural products have been a rich source of compounds for drug discovery. However, their use has diminished in the past two decades, in part because of technical barriers to screening natural products in high-throughput assays against molecular targets. Here, we review strategies for natural product screening that harness the recent technical advances that have reduced these barriers. We also assess the use of genomic and metabolomic approaches to augment traditional methods of studying natural products, and highlight recent examples of natural products in antimicrobial drug discovery and as inhibitors of protein-protein interactions. The growing appreciation of functional assays and phenotypic screens may further contribute to a revival of interest in natural products for drug discovery.
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Affiliation(s)
- Alan L Harvey
- 1] Research and Innovation Support, Dublin City University, Dublin 9, Ireland. [2] Strathclyde Institute of Pharmacy and Biomedical Science, University of Strathclyde, Glasgow G4 0NR, UK
| | - RuAngelie Edrada-Ebel
- Strathclyde Institute of Pharmacy and Biomedical Science, University of Strathclyde, Glasgow G4 0NR, UK
| | - Ronald J Quinn
- Eskitis Institute for Drug Discovery, Griffith University, Brisbane, Queensland 4111, Australia
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Ko K, Lee SH, Kim SH, Kim EH, Oh KB, Shin J, Oh DC. Lajollamycins, nitro group-bearing spiro-β-lactone-γ-lactams obtained from a marine-derived Streptomyces sp. JOURNAL OF NATURAL PRODUCTS 2014; 77:2099-2104. [PMID: 25211234 DOI: 10.1021/np500500t] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Lajollamycins (1-4), each of which bears a spiro-β-lactone-γ-lactam ring and a nitro-tetraene moiety, were obtained from a marine-derived Streptomyces strain isolated from the southern area of Jeju Island, Republic of Korea. The planar structures of the lajollamycins were elucidated on the basis of spectroscopic analyses by NMR, UV, IR, and MS. The absolute configuration of lajollamycin (1), the planar structure of which has been previously reported, was determined using J-based configuration analysis based on (1)H-(1)H and (1)H-(13)C coupling constants, as well as ROESY correlations, followed by the modified Mosher's method. The absolute configurations of lajollamycins B-D (2-4) were established by comparing their CD spectra with that of 1. The lajollamycins exhibited moderate inhibitory activity toward Candida albicans isocitrate lyase.
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Affiliation(s)
- Keebeom Ko
- Natural Products Research Institute, College of Pharmacy, Seoul National University , 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea
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Resistant traits in digital organisms do not revert preselection status despite extended deselection: implications to microbial antibiotics resistance. BIOMED RESEARCH INTERNATIONAL 2014; 2014:648389. [PMID: 24977157 PMCID: PMC4054778 DOI: 10.1155/2014/648389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 04/29/2014] [Accepted: 05/07/2014] [Indexed: 11/25/2022]
Abstract
Antibiotics resistance is a serious biomedical issue as formally susceptible organisms gain resistance under its selective pressure. There have been contradictory results regarding the prevalence of resistance following withdrawal and disuse of the specific antibiotics. Here, we use experimental evolution in “digital organisms” to examine the rate of gain and loss of resistance under the assumption that there is no fitness cost for maintaining resistance. Our results show that selective pressure is likely to result in maximum resistance with respect to the selective pressure. During deselection as a result of disuse of the specific antibiotics, a large initial loss and prolonged stabilization of resistance are observed, but resistance is not lost to the stage of preselection. This suggests that a pool of partial persists organisms persist long after withdrawal of selective pressure at a relatively constant proportion. Hence, contradictory results regarding the prevalence of resistance following withdrawal and disuse of the specific antibiotics may be a statistical variation about constant proportion. Our results also show that subsequent reintroduction of the same selective pressure results in rapid regain of maximal resistance. Thus, our simulation results suggest that complete elimination of specific antibiotics resistance is unlikely after the disuse of antibiotics once a resistant pool of microorganisms has been established.
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Discovery of potent broad spectrum antivirals derived from marine actinobacteria. PLoS One 2013; 8:e82318. [PMID: 24349254 PMCID: PMC3857800 DOI: 10.1371/journal.pone.0082318] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 10/29/2013] [Indexed: 11/19/2022] Open
Abstract
Natural products provide a vast array of chemical structures to explore in the discovery of new medicines. Although secondary metabolites produced by microbes have been developed to treat a variety of diseases, including bacterial and fungal infections, to date there has been limited investigation of natural products with antiviral activity. In this report, we used a phenotypic cell-based replicon assay coupled with an iterative biochemical fractionation process to identify, purify, and characterize antiviral compounds produced by marine microbes. We isolated a compound from Streptomyces kaviengensis, a novel actinomycetes isolated from marine sediments obtained off the coast of New Ireland, Papua New Guinea, which we identified as antimycin A1a. This compound displays potent activity against western equine encephalitis virus in cultured cells with half-maximal inhibitory concentrations of less than 4 nM and a selectivity index of greater than 550. Our efforts also revealed that several antimycin A analogues display antiviral activity, and mechanism of action studies confirmed that these Streptomyces-derived secondary metabolites function by inhibiting the cellular mitochondrial electron transport chain, thereby suppressing de novo pyrimidine synthesis. Furthermore, we found that antimycin A functions as a broad spectrum agent with activity against a wide range of RNA viruses in cultured cells, including members of the Togaviridae, Flaviviridae, Bunyaviridae, Picornaviridae, and Paramyxoviridae families. Finally, we demonstrate that antimycin A reduces central nervous system viral titers, improves clinical disease severity, and enhances survival in mice given a lethal challenge with western equine encephalitis virus. Our results provide conclusive validation for using natural product resources derived from marine microbes as source material for antiviral drug discovery, and they indicate that host mitochondrial electron transport is a viable target for the continued development of broadly active antiviral compounds.
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