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Mutant Selection Windows of Azalomycin F5a in Combination with Vitamin K3 against Methicillin-Resistant Staphylococcus aureus  [PDF]
Xuejie Xu, Xuejiao Wu, Ganjun Yuan, Li Xu, Yimin Wang
Journal of Biosciences and Medicines (JBM) , 2016, DOI: 10.4236/jbm.2016.412020
Abstract: Azalomycin F5a, a 36-membered macrocyclic lactone isolated from several streptomyces strains, presented remarkable anti-methicillin-resistant Staphylococcus aureus (MRSA) activities. To improve its anti-MRSA potential and to evaluate the probability of MRSA resistant to it before development, the anti-MRSA activities of azalomycin F5a in combination with vitamin K3 were first evaluated using checkerboard assay. Then the minimal concentration inhibiting colony formation by 99% (MIC99) and mutant prevention concentration (MPC) of azalomycin F5a alone and in combination with vitamin K3 against MRSA were determined using agar plates with linear antimicrobial concentration decrease. The fractional inhibitory concentration indexes (FICIs) of 0.25 - 0.50 showed the synergistic activity of azalomycin F5a in combination with vitamin K3. The mutant selection windows (MSWs, MIC99-MPC) of azalomycin F5a alone against MRSA tested were 2.07 - 6.40 μg/mL, and the MPCs of azalomycin F5a in combination with vitamin K3 against MRSA tested were 1.60 - 3.20 μg/mL. These indicated that the MPCs of azalomycin F5a in combination could drop down to below its MIC99 alone. According to the hypothesis of MSW, the narrower MSWs of azalomycin F5a alone, even closed MSWs in combination with vitamin K3, together with their synergistic anti-MRSA activities, indicated that azalomycin F5a had a good potential to develop as a new antimicrobial agent.
Mining of the Pyrrolamide Antibiotics Analogs in Streptomyces netropsis Reveals the Amidohydrolase-Dependent “Iterative Strategy” Underlying the Pyrrole Polymerization  [PDF]
Chunlin Hao, Sheng Huang, Zixin Deng, Changming Zhao, Yi Yu
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0099077
Abstract: In biosynthesis of natural products, potential intermediates or analogs of a particular compound in the crude extracts are commonly overlooked in routine assays due to their low concentration, limited structural information, or because of their insignificant bio-activities. This may lead into an incomplete and even an incorrect biosynthetic pathway for the target molecule. Here we applied multiple compound mining approaches, including genome scanning and precursor ion scan-directed mass spectrometry, to identify potential pyrrolamide compounds in the fermentation culture of Streptomyces netropsis. Several novel congocidine and distamycin analogs were thus detected and characterized. A more reasonable route for the biosynthesis of pyrrolamides was proposed based on the structures of these newly discovered compounds, as well as the functional characterization of several key biosynthetic genes of pyrrolamides. Collectively, our results implied an unusual “iterative strategy” underlying the pyrrole polymerization in the biosynthesis of pyrrolamide antibiotics.
Occurrence of Streptomyces aurantiacus in Mangroves of Bhitarkanika  [PDF]
Gupta, N.,Mishra, S.,Basak, U. C.
Malaysian Journal of Microbiology , 2007,
Abstract: Thirteen strains of Streptomyces were isolated from phyllosphere of nine mangrove tree species found in Bhitarkanika mangrove ecosystem of Orissa. According to physiological, biochemical data, all 13 of the isolates were taxonomically identified to the genus Streptomyces as aurantiacus species. All strains are grayish, spirals and forming amorphous colony. Almost all utilized araginose, produced H2S, resistant towards rifampicin and penicillin, urea except few strains. However, they exhibited different extracellular activity like phosphate solubilization, lipase and L asparaginase production. This is a unique report from this mangrove ecosystem as far as Streptomyces occurrence is concerned.
Diversity of Streptomyces in mangrove ecosystem of Bhitarkanika
Nibha Gupta,S Mishra,UC Basak
Iranian Journal of Microbiology , 2009,
Abstract: Background and objective: Bhitarkanika is the mangrove ecosystem of Orissa, India. It was not explored before for occurrence"nand distribution of Streptomyces. With the aim of isolation and characterization of special group of bacteria from this"nmangrove ecosystem, the present study has been made."nMaterials and Methods: Isolates of Streptomyces were obtained from plant, soil and water collected from Bhitarkanika"nmangroves on specific ISP media. Different isolates of Streptomyces were characterized for their colony characteristics,"nmorphological properties, physiological and biochemical properties and were tentatively identified."nResults: 105 isolates of Streptomyces belonging to 20 different species were isolated from 19 mangrove plants in different"nlocations of Bhitarkanika mangroves. According to physiological and biochemical data, all strains were taxonomically identified"nto the genus Streptomyces. However, all the strains were morphologically varied and exhibited different extracellular"nactivity. Maximum number of Streptomyces species was observed in the Khola region. S. xanthochromogenes was found to"nbe most prevalent species followed by S. exfoliates and S. auranticus."nConclusion: We have confirmed occurrence and distribution of Streptomyces in the Bhitarkanika mangrove environment."nThis is the first report of Streptomyces biodiversity in mangrove ecosystem of Bhitarkanika.
Salt tolerant culturable microbes accessible in the soil of the Sundarban Mangrove forest, India  [PDF]
Subhajit Das, Minati De, Raghab Ray, Dipnarayan Ganguly, Tapan kumar Jana, Tarun Kumar De
Open Journal of Ecology (OJE) , 2011, DOI: 10.4236/oje.2011.12004
Abstract: Sundarban Mangrove forest is highly productive marine ecosystem where halophilic microbes actively participate in bio-mineralization and biotransformation of minerals. The population of aerobic halophilic microbes was studied to determine their distribution with the availability of different physicochemical parameters with increasing depth of this forest sediment. The present study revealed that microbes present in the top soil region were less tolerant to fluctuation in salinity than the middle and bottom segment. Microbes isolated from bottom segment showed higher growth rate in anaerobic condition. A decreasing trend of total microbial population and organic carbon content of soil were found with increase in depth. In contrary a reverse profile was found for salinity. A significant stratification was found to exist among microbial population and the salty nature of the soil of Sundarban Mangrove forest.
A Novel Benzo[f][1,7]Naphthyridine Produced by Streptomyces Albogriseolus from Mangrove Sediments  [PDF]
Xiao-Ling Li,Min-Juan Xu,Yi-Lei Zhao,Jun Xu
Molecules , 2010, DOI: 10.3390/molecules15129298
Abstract: Mangrove Streptomyces represent a rich source of novel bioactive compounds in medicinal research. A novel alkaloid, named 1-N-methyl-3-methylamino-[N-butanoic acid-3¢-(9¢-methyl-8¢-propen-7¢-one)-amide]-benzo[f][1,7]naphthyridine-2-one (1) was isolated from Streptomyces albogriseolus originating from mangrove sediments. The structure of compound 1 was elucidated by extensive spectroscopic data analyses and verified by the 13C-NMR calculation at the B3LYP/6-311+G(2d,p) level of theory.
Polythene and Plastics-degrading microbes from the mangrove soil
Kathiresan,K;
Revista de Biología Tropical , 2003,
Abstract: biodegradation of polythene bags and plastic cups was analyzed after 2, 4, 6, and 9 months of incubation in the mangrove soil. the biodegradation of polythene bags was significantly higher (up to 4.21% in 9 months) than that of plastic cups (up to 0.25% in 9 months). microbial counts in the degrading materials were recorded up to 79.67 x 10 4 per gram for total heterotrophic bacteria, and up to 55.33 x 10 2 per gram for fungi. the microbial species found associated with the degrading materials were identified as five gram positive and two gram negative bacteria, and eight fungal species of aspergillus. the species that were predominant were streptococcus, staphylococcus, micrococcus (gram +ve), moraxella, and pseudomonas (gram -ve) and two species of fungi (aspergillus glaucus and a. niger). efficacy of the microbial species in degradation of plastics and polythene was analyzed in shaker cultures. among the bacteria, pseudomonas species degraded 20.54% of polythene and 8.16% of plastics in one-month period. among the fungal species, aspergillus glaucus degraded 28.80% of polythene and 7.26% of plastics in one-month period. this work reveals that the mangrove soil is a good source of microbes capable of degrading polythene and plastics
Chemical Analyses of Wasp-Associated Streptomyces Bacteria Reveal a Prolific Potential for Natural Products Discovery  [PDF]
Michael Poulsen,Dong-Chan Oh,Jon Clardy,Cameron R. Currie
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0016763
Abstract: Identifying new sources for small molecule discovery is necessary to help mitigate the continuous emergence of antibiotic-resistance in pathogenic microbes. Recent studies indicate that one potentially rich source of novel natural products is Actinobacterial symbionts associated with social and solitary Hymenoptera. Here we test this possibility by examining two species of solitary mud dauber wasps, Sceliphron caementarium and Chalybion californicum. We performed enrichment isolations from 33 wasps and obtained more than 200 isolates of Streptomyces Actinobacteria. Chemical analyses of 15 of these isolates identified 11 distinct and structurally diverse secondary metabolites, including a novel polyunsaturated and polyoxygenated macrocyclic lactam, which we name sceliphrolactam. By pairing the 15 Streptomyces strains against a collection of fungi and bacteria, we document their antifungal and antibacterial activity. The prevalence and anti-microbial properties of Actinobacteria associated with these two solitary wasp species suggest the potential role of these Streptomyces as antibiotic-producing symbionts, potentially helping defend their wasp hosts from pathogenic microbes. Finding phylogenetically diverse and chemically prolific Actinobacteria from solitary wasps suggests that insect-associated Actinobacteria can provide a valuable source of novel natural products of pharmaceutical interest.
Enterococci: yin - yang microbes  [cached]
Andreja ?an?ek Majheni?
Mljekarstvo , 2006,
Abstract: This review deals with the duality of enterococci, which can be illustrated by their yin - yang behaviour. The rough nature of this specific group of lactic acid bacteria promotes their dissemination in various environments where they significantly influence the outcome of a certain process. In the technological meaning, enterococci are leading microbes in fermentation processes of traditional foods, where their detrimental spoilage activities are equally significant. As therapeutics, enterococci manifest the probiotic properties through their positive effects on maintaining of the normal intestinal microflora, on stimulation of the immune system, on improved nutritional value of food and with the production of antimicrobial compounds (bacteriocins). At the same time, enterococci present an emerging pool of opportunistic pathogens for humans as they cause disease, possess agents for antibiotic resistance and their transfer mechanisms, and are frequently armed with potential virulence factors. Despite the yin - yang characteristics of enterococci, the long history of safe use of certain strains of enterococci in food/feed, and reliable identification and classification of enterococci with phenotypic methods supported with modern genetic tools, enables selection of promising enterococci, which could be safely used as starter cultures or food/feed additives.
Effect of microbes on karstification in karst ecosystems
Bin Lian,DaoXian Yuan,ZaiHua Liu
Chinese Science Bulletin , 2011, DOI: 10.1007/s11434-011-4648-z
Abstract: The role of microbes in the karstification process was determined based on the karst dynamics, CO2 capture, and carbonate deposition. A close relationship was found among microbial activity, karst dynamics and stability, and the carbon cycle in a karst ecosystem. More in-depth studies were needed to investigate the impact of microbes on karst dynamics within different eco-environments under natural conditions to determine the response of biological organisms to a changing environment, as well as the relationship between microbial organisms and the karstification process.
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