Screening and identification of novel isolate Streptomyces sp., NLKPB45 from Nellore costal region for its biomedical applications

Actinobacteria, which are the prolific producers of antibiotics and significant suppliers to the pharmaceutical industry, can produce a wide variety of bioactive metabolites. An actinomycete strain designated NLKPB45 was isolated from mangrove soils samples of Nellore coastal regions Andhra Pradesh and assessed for antibiotic production and activity against pathogenic bacteria. From a total of 9 mangrove soil samples, 143 acinomycetes were isolated. Among the isolated them 6 actinomycetes strains showed potential antibacterial activity against at two tested pathogens gram positive and gram negative bacteria E. coli and S. aureus. The potent strain NLKPB45 was identified by 16S gene isolation and sequencing to the Streptomyces genus. The ethyl acetate extracts also as shown excellent antimicrobial activity against Salmonella sp., staphylococcus aureus, E. coli, and B. subtilus were detected in both the supernatant extract samples from fermentations of culture NLKPB45. The anticancer activity of extracts in the HeLa with IC₅₀ value of 37.1924 μg/ml, MCF-7 IC₅₀ value of 40.9177 μg/ml and HT 29 IC₅₀ value of 43.3758 μg/ml.     

In vitro biological properties of Streptomyces cangkringensis isolated from the floral rhizosphere regions

This context was investigated to determine in vitro antimicrobial, antioxidative, and anticancer traits of crude ethyl acetate extract of Streptomyces cangkringensis strain TSAS 04 isolated from soil sample of rhizosphere regions. The antimicrobial activity of ethyl acetate extract of strain TSAS 04 was determined against indicator pathogens using disc diffusion assay which exhibited maximum zones of inhibition of 20.6 ± 0.3 and 16.3 ± 0.6 mm against Bacillus subtilis and Trichoderma viride, respectively. In vitro antioxidant properties of the crude ethyl acetate extract were performed using standard methodologies. The extract revealed maximum DPPḢ and ABTS⁺ radical scavenging activities of 51.1 ± 0.39 and 81.25 ± 0.33%, respectively. Likewise, maximum phosphomolybdenum reduction and Fe³⁺ reduction of the crude ethyl acetate extract of strain TSAS 04 were estimated 76.18 ± 0.10 and 89.01 ± 0.44%, respectively. In vitro anticancer trait of the extract was determined against HeLa cell line using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay which showed anticancer activities in a dose dependent manner with an IC₅₀ value of 410.5 µg/mL. Fourier transform infrared spectroscopy (FT-IR) and Gas chromatography–mass spectrometry (GC-MS) analyses indicated the presence of distinct functional groups and bioactive components in the extract, respectively. In conclusion, S. cangkringensis strain TSAS 04 showed its effectiveness as ideal bioactive agent by exhibiting substantial antimicrobial, antioxidant, and anticancer properties.     

Optimization and production of novel antimicrobial agents from sponge associated marine actinomycetes <Emphasis Type="Italic">Nocardiopsis dassonvillei</Emphasis> MAD08

The sponge-associated actinomycetes were isolated from the marine sponge Dendrilla nigra, collected from the southwest coast of India. Eleven actinomycetes were isolated depending upon the heterogeneity and stability in subculturing. Among these, Nocardiopsis dassonvillei MAD08 showed 100% activity against the multidrug resistant pathogens tested. The culture conditions of N. dassonvillei MAD08 was optimized under submerged fermentation conditions for enhanced antimicrobial production. The unique feature of MAD08 includes extracellular amylase, cellulase, lipase, and protease production. These enzymes ultimately increase the scope of optimization using broad range of raw materials which might be efficiently utilized. The extraction of the cell free supernatant with ethyl acetate yielded bioactive crude extract that displayed activity against a panel of pathogens tested. Analysis of the active thin layer chromatography fraction by Fourier transform infrared and gas chromatography-mass spectrometry evidenced 11 compounds with antimicrobial activity. The ammonium sulfate precipitation of the culture supernatant at 80% saturation yielded an anticandidal protein of molecular weight 87.12 kDa. This is the first strain that produces both organic solvent and water soluble antimicrobial compounds. The active extract was non-hemolytic and showed surface active property envisaging its probable role in inhibiting the attachment of pathogens to host tissues, thus, blocking host–pathogen interaction at an earlier stage of pathogenesis.     

Broad-spectrum In vitro antimicrobial activities of Streptomyces sp. strain BCNU 1001

Streptomyces sp. strain BCNU 1001 was isolated from forest soil samples. Cultural, morphological, and physiological characteristics as well as 16S rDNA analysis revealed that the isolate, BCNU 1001, belonged to the genus Streptomyces. The antimicrobial activity of the ethyl acetate extract was confirmed using the broth microdilution technique. The minimum inhibitory concentration (MIC) of the BCNU 1001 ethyl acetate extract was 0.25 mg/mL for Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa, and 0.125 mg/mL for Micrococcus luteus, Staphylococcus aureus, and Pseudomonas fluorescens. The MIC of the BCNU 1001 ethyl acetate extract for Aspergillus niger, Candida albicans, and Saccharomyces cerevisiae was 0.5, 0.125, and 0.25 mg/mL, respectively. BCNU 1001 was also active against dermatophytic fungi such as Trichophyton mentagrophytes and T. rubrum. Furthermore, BCNU 1001 was also found to be effective against Methicillin-resistant Staphylococcus aureus (MRSA), and its ethyl acetate extract showed MIC = 0.5 mg/mL against MRSA. The most abundant antimicrobial compound was identified as a 2-hydroxybenzyl alcohol through analysis utilizing a nuclear magnetic resonance spectroscopy. This compound was seen to be very effective against some kinds of bacteria and fungi.     

Antimicrobial potential of phylogenetically unique actinomycete,Streptomyces sp. JRG-04 from marine origin

Due to the emergence of severe infectious diseases and thriving antibiotic resistance, there is a need to explore microbial-derived bioactive secondary metabolites from unexplored regions. Present study deals with a mangrove estuary derived strain of Streptomyces sp. with potent antimicrobial activity against various pathogens, including methicillin resistant Staphylococcus aureus. Bioactive compound was effective even at low MIC level, damages the membrane of methicillin resistant S. aureus and causes cell death, however it has no cytotoxic effect on H9C2 cells. 16S rRNA shared 99.5% sequence similarity to Streptomyces longispororuber. Optimum biomass and antimicrobial compound production were observed in production medium supplemented with 1.0% maltose and 0.5% yeast extract. The active compound purified from the chloroform extract of the cell-free supernatant was studied by FT-IR, 1H NMR, 13C NMR and LC ESI-MS and identified as aromatic polyketide. β-ketosynthase (KS) domain of the Streptomyces strain revealed 93.2% sequence similarity to the benzoisochromanequinone, an actinorhodin biosynthetic gene cluster of Streptomyces coelicolor A3(2). However, the region synthesizing the secondary metabolite produced by the S. longispororuber was not related to the KS domain of the strain, due to the phenomenon of horizontal gene transfer over the period of evolutionary process, thus generating metabolic compound diversity.     

Isolation of antimicrobial producing Actinobacteria from soil samples

Emergence of multidrug resistant bacteria has made the search for novel bioactive compounds from natural and unexplored habitats a necessity. Actinobacteria have important bioactive substances. The present study investigated antimicrobial activity of Actinobacteria isolated from soil samples of Egypt. One hundred samples were collected from agricultural farming soil of different governorates. Twelve isolates have produced activity against the tested microorganisms (S. aureus, Bacillus cereus, E. coli, K. pneumoniae, P. aeruginosa, S. Typhi, C. albicans, A. niger and A. flavus). By VITEK 2 system version: 07.01 the 12 isolates were identified as Kocuria kristinae, Kocuria rosea, Streptomyces griseus, Streptomyces flaveolus and Actinobacteria. Using ethyl acetate extraction method the isolates culture’s supernatants were tested by diffusion method against indicator microorganisms. These results indicate that Actinobacteria isolated from Egypt farms could be sources of antimicrobial bioactive substances.     

Isolation and characterization of antiprotozoal compound-producing Streptomyces species from Mongolian soils

Natural resources are recognized as important sources of potential drugs for treating various infections, and microorganisms are a rich natural source of diverse compounds. Among the world's microorganisms, actinomycetes, which are abundant in soil and marine, are the well-known producers of a wide range of bioactive secondary metabolites and antibiotics. In the present study, four actinomycetes (samples N25, N6, N18, and N12) were isolated from soil samples in Mongolia. Phylogenetic analysis of these isolates revealed that they share the highest similarity with Streptomyces canus (N25), S. cirratus (N6), S. bacillaris (N18) and S. peucetius (N12), based on 16S rRNA gene sequencing. Crude extracts were obtained from them using ethyl acetate, and the crude fractions were separated by thin layer chromatography. The fractions were then evaluated for their cytotoxicities and their anti-Toxoplasma and antimalarial activities in vitro. The S. canus (N25) crude extract was selected for further chemical characterization based on its antiprotozoal activities. Using liquid chromatography-high resolution mass spectrometry, phenazine-1-carboxylic acid (PCA) was detected and identified in the active fractions of the metabolites from strain N25. We next confirmed that commercially available PCA possesses antiprotozoal activity against T. gondii (IC₅₀: 55.5 μg/ml) and Plasmodium falciparum (IC₅₀: 6.4 μg/ml) in vitro. The results of this study reveal that soil actinomycetes are potential sources of antiprotozoal compounds, and that PCA merits further investigation as an anti-protozoal agent.     

Culturable actinomycetes from desert ecosystem in northeast of Qinghai-Tibet Plateau

In this study, 53 actinomycetes strains were isolated from desert ecosystems located in northeast of Qinghai-Tibet Plateau and grouped into four RFLP patterns. Twenty-six actinomycetes with obvious morphology differences were chosen for phylogenetic diversity study and antimicrobial testing. As a result, the 16S rRNA gene sequencing showed that these strains belonged to Streptomyces, Micromonospora, Saccharothrix, Streptosporangium and Cellulomonas, and that most of the strains had antimicrobial bioactivity. The PKS and NRPS genes detection indicated diversified potential bioactive products of actinomycetes in this ecosystem. Among these strains, Sd-31 was chosen to study the bioactive products using HPLC-MS because of its optimum antimicrobial bioactivity. The result showed that it might produce Granatomycin A, Granatomycin C, and an unknown compound.     

Molecular characterization of rhizospheric soil streptomycetes isolated from indigenous Turkish plants and their antimicrobial activity

As part of a research program whose aim is to determine the diversity of streptomycetes in order to discover new bioactive secondary metabolites, rhizosphere soils of three indigenous plants were analyzed. A total of 55 actinomycetes were isolated using three different medium from the samples. The rhizospheric soil of the plant Aethionema dumanii gave the highest number of actinomycetes, i.e., 42% versus 27% and 31% for the soils from Salvia aytachii and Achillea ketenoglui, respectively. The AIA is the most favorable medium for the isolation of the actinomycetes from different rhizospheric soils. 16S rDNA sequence analysis revealed that while some isolates belong to different cluster groups such as Streptomyces lydicus, S. rochei, S. microflavus, S. griseoflavus, S. albidoflavus and S. violaceusniger, the majority of the sequences did not considerable clustered with the member of different Streptomyces groups. The in vitro antimicrobial activities of the crude organic and aqueous extracts of isolates were screened using a disc diffusion assay against a panel of bacteria and C. albicans. A total of 22 isolates showed antimicrobial activity. The antibacterial action of the extracts is more pronounced on Gram-positive than on Gram-negative bacteria in most cases. About 18% of the actinomycetes showed also antifungal activity. Study of the influence of two different culture media on production of bioactive molecules showed that the higher antimicrobial activity was obtained in M2 when compared to TSB. The results from this study provide evidence that the streptomycetes in the rhizosphere soils could be promising sources for antimicrobial bioactive agents.     

Microbicidal and anti-inflammatory effects of Actinomadura spadix (EHA-2) active metabolites from Himalayan soils, India

Actinomycetes play an essential role in producing several bioactive compounds. In the present study, microbicidal and anti-inflammatory effects of metabolites from actinomycetes were investigated. Actinomycetes were isolated from north eastern Himalayan soil samples, India. The actinomycetes were investigated for their microbicidal property by conventional method and the active actinomycetes were identified by 16s rDNA sequence analyses. Further the metabolites were extracted and fractionated to evaluate the antimicrobial potency; they were subjected to GC–MS analysis. The active fraction was evaluated for selective toxicity and anti-inflammatory potential. Among isolated actinomycetes, EHA-2 showed potent antimicrobial activity and was identified as Actinomadura spadix. Fraction-8 from ethyl acetate extract of EHA-2 showed 100 % inhibition against Candida sp. (MIC—80 μg/mL) and Enterococcus faecalis (MIC—80 μg/mL). The expression of GAPDH in primary cells and 16s rRNA levels on E. faecalis treated with fraction-8 revealed no toxicity to the primary cells. Fraction-8 also suppressed the paw thickness on carrageenan induced animals and also controlled the release of NO, TNFα and IL-1β levels on LPS induced RAW 264.7 cell lines. GC–MS profile of fraction-8 showed the presence of an antimicrobial agent 3,6 di-isobutyl 2,5 piperazinedione, which is the first report in A. spadix. The actinomycetes isolate EHA-2 can be proceed further to produce antibiotics.     

Antifouling activity of sessile bacilli derived from marine surfaces

Marine biofilms are a virtually untapped source of bioactive molecules that may find application as novel antifoulants in the marine paint industry. This study aimed at determining the potential of marine biofilm bacteria to produce novel biomolecules with potential application as natural antifoulants. Nine representative strains were isolated from a range of surfaces and were grown in YEB medium and harvested during the late exponential growth phase. Bacterial biomass and spent culture medium were extracted with ethanol and ethyl acetate, respectively. Extracts were assayed for their antifouling activity using two tests: (1) antimicrobial well diffusion test against a common fouling bacterium, Halomonas marina, and (2) anti-crustacean activity test using Artemia salina. Our results showed that none of the ethanolic extracts (bacterial biomass) were active in either test. In contrast, most of the organic extracts had antimicrobial activity (88%) and were toxic towards A. salina (67%). Sequencing of full 16 S ribosomal DNA analysis showed that the isolates were related to Bacillus mojavensis and Bacillus firmus. Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF-MS) profiling of ethyl acetate extracts of culture supernatants showed that these species produce the bioactive lipopeptides surfactin A, mycosubtilin and bacillomycin D.     

Antimicrobial Activity of Marine Bacterial Symbionts Retrieved from Shallow Water Hydrothermal Vents

Marine sponges and other sessile macro-organisms were collected at a shallow water hydrothermal site in Eyjafjörður, Iceland. Bacteria were isolated from the organisms using selective media for actinomycetes, and the isolates were screened for antimicrobial activity. A total of 111 isolates revealed antimicrobial activity displaying different antimicrobial patterns which indicates production of various compounds. Known test strains were grown in the presence of ethyl acetate extracts from one selected isolate, and a clear growth inhibition of Staphylococcus aureus was observed down to 0.1 % extract concentration in the medium. Identification of isolates shows different species of Actinobacteria with Streptomyces sp. playing the largest role, but also members of Bacilli, Alphaproteobacteria and Gammaproteobacteria. Sponges have an excellent record regarding production of bioactive compounds, often involving microbial symbionts. At the hydrothermal vents, however, the majority of active isolates originated from other invertebrates such as sea anemones or algae. The results indicate that antimicrobial assays involving isolates in full growth can detect activity not visible by other methods. The macro-organisms inhabiting the Eyjafjörður hydrothermal vent area host diverse microbial species in the phylum Actinobacteria with antimicrobial activity, and the compounds responsible for the activity will be subject to further research.     

In vitro antioxidant,antimicrobial and antiproliferative studies of four different extracts of Orthosiphon stamineus,Gynura procumbens and Ficus deltoidea

BackgroundMedicinal plants are important source of drugs with pharmacological activities. Therefore, there is always rising demands to discover more therapeutic agents from various species. Orthosiphon stamineus, Gynura procumbens and Ficus deltoidea are high valued medicinal plants of Malaysia contain rich source of phenolic and flavonoid compounds. The aims of the present study were to evaluate anti-oxidant, antimicrobial and anti-proliferative effects on A549, HePG2 and MCF7 cell lines of four different extracts of Orthosiphon stamineus, Gynura procumbens and Ficus deltoidea.MethodologyThe leaves of all selected plants were extracted with methanol, chloroform, ethyl acetate and butanol separately with simple cold maceration. Antioxidant activity of all crude extracts were quantitatively measured against DPPH and Ferric Reducing Assay. Antimicrobial evaluation was done by Microdilution and MTT assay and antipoliferative activity of all extracts of selected plant were evaluated against A549, HePG2 and MCF7 cell lines.ResultsResults showed that methanol extract exhibited highest percentage free radical scavenging activity of almost all extracts of selected plants. Antimicrobials results showed chloroform and methanol extracts of O. stamineus extract were the two most active extracts against resistant MRSA but not S. aureus. Only methanol extract of G. procumbens showed antimicrobial activity against the tested pathogens. Chloroform and methanol extracts of F. deltoidea elicited antimicrobial activity against S. aureus but not MRSA. Antiproliferative activity against three tested cell lines results showed that ethyl acetate extract of O. stamineus showed good effect whereas methanol extract of F. deltoidea and G. procumbens exhibited good antiproliferative activity.ConclusionsThe results of the present investigation demonstrated significant variations in the antioxidant, antimicrobial and antiproliferative effects of different solvent extracts. These data could be helpful in isolation of pure potent compounds with good biological activities from the extracts of plants.     

Molecular profiling of marine endophytic fungi from green algae: Assessment of antibacterial and anticancer activities

Bioactive natural metabolites, especially from the marine endophytic fungi, are largely unexplored. Endophytic fungi are being increasingly recognized as a group of organisms that produce novel metabolites of industrial importance. This study investigated the anticancer and antibacterial potential of the marine algal endophyte, Penicillium chrysogenum. The different organic solvent extracts of the endophytic fungi grown on different growth medium were analyzed for anticancer and antibacterial activities. The highest inhibitory activity was observed for the ethyl acetate (EA) extract of the culture filtrate grown in potato dextrose broth (PDB) for 21 days, against the tested human breast cancer cell (MCF-7) line. Similarly, the PDB-EA extract showed an appreciable activity against the human pathogens. The biochemical analysis of the Cha EA metabolites revealed terpenoids, steroids, phenolics and flavones. Gas Chromatography (GCMS) data revealed several bioactive compounds such as anthraquinone and cinnamic acid. The Cha EA extract induced membrane damage and thus, apoptosis in MCF-7cells. The secondary metabolites produced by these marine endophytic fungi have contributed to considerable anticancer and antimicrobial activities and hence, this study is an evidence of potential sources of antimicrobial and anticancer compounds from Penicillium chrysogenum.     

Identification of Streptomyces sp. nov. WH26 producing cytotoxic compounds isolated from marine solar saltern in China

A moderately halophilic actinomycetes strain, designated as WH26, was isolated from Weihai Solar Saltern in China. The identification of the strain WH26 was performed by its morphological characteristics, physiological and biochemical tests as well as phylogenetic analysis based on 16S rRNA sequence comparison. The results showed that the nucleotide sequence of the 16S rRNA gene (1,677 bp) of the strain WH26 exhibited close similarity (97–99 %) with other Streptomyces 16S rRNA genes and the strain WH26 was identified to belong to the genus Streptomyces. An ethyl acetate extraction of Streptomyces sp. nov. WH26 demonstrated significant cellular toxicity. Two compounds, 8-O-methyltetrangulol and naphthomycin A were isolated from the extract via silica gel column chromatography and HPLC. These two compounds showed potent cytotoxic activity against several human tumor cell lines including A549, HeLa, BEL-7402 and HT-29. The present studies suggest that moderately halophilic actinomycetes may be a novel biological source for the discovery of anticancer agents.     

Phytotoxic activity of Cleome arabica L. and its principal discovered active compounds

The aim of this study was to assess the phytotoxic potential of Cleome arabica L, as well as to isolate the main bioactive compounds. Phytotoxicity was evaluated on germination and seedling growth of Lactuca sativa, Raphanus sativus, Peganum harmala and Silybum marianum, through testing aqueous and organic extracts of different C. arabica organs (roots, shoots, siliquae and seeds). Results showed that siliquae methanol extract caused the greatest negative effect on lettuce germination and growth. For the bioactive subfractions (petroleum ether, ethyl acetate and methanol–water), the ethyl acetate induced highly significant reduction, showing 100% inhibition of lettuce growth at 6 g/L. The bioactive ethyl acetate subfraction was chromatographed and subjected to NMR techniques. Based on bio-guided chromatographic fractionation, five bioactive allelochemical compounds were isolated from ethyl acetate extract of siliquae of C. arabica. The most inhibitory compound on lettuce seedling growth was elucidated as 11-α-acetylbrachy-carpone-22(23)-ene.     

Antimicrobial activity and phytochemical screening of Ocimum americanum L extracts against pathogenic microorganisms

The aim of the present study is to assess the antimicrobial activities of various leaf extracts of Ocimum americanum were tested against pathogenic microorganisms. Preparation of different extracts viz., aqueous, acetone, ethyl acetate and methanol through soxhlet extraction method. Various extracts were investigated against MTCC strains of Bacillus cereus, Clostridium penfrigens, Klebsilla pnemoniae, Salmonella paratyphi, Candida albicans and Aspergillus niger by agar well diffusion and disc diffusion methods. Minimum inhibitory concentration (MIC), Minimum Bactericidal/Fungicindal Concentration (MBC/MFC) were determined through micro dilution method. Elucidation of phytochemicals and functional groups were observed by HPLC and FT-IR respectively. Ethyl acetate leaf extract of O.americanum showed significant antimicrobial activity against the all tested pathogens in agar well diffusion method in which B.cereus (17 mm) was observed high zone of inhibition. Whereas lowest inhibition was observed in aqueous extract against C.pentrigens (7 mm). The ranges of MIC values from 0.78 μg/ml to 50 μg/ml and MBC/MFC 1.56 μg/ml to 50 μg/ml were observed. Phytochemicals such as alkaloids, steroids, saponins, flavonoids, tannins, terepenes, phenolic compounds cardiac glycosides were detected. Saponinns, flavonoids, tannins, phenolic compounds were observed in only ethyl acetate leaf extracts. Functional group of the leaf extracts was exhibited by FTIR and HPLC analysis of the ethyl acetate leaf extract was elutated at six peaks. Based on the results we concluded that ethyl acetate leaf extract of O.americanum has proved to be potentially effective than the other extracts. Therefore, ethyl acetate leaf extract of O.americanum could act as antimicrobial agent and further studies are recommended for isolation of compounds and toxicological studies.     

The Diversity and Anti-Microbial Activity of Endophytic Actinomycetes Isolated from Medicinal Plants in Panxi Plateau,China

Traditional Chinese medicinal plants are sources of biologically active compounds, providing raw material for pharmaceutical, cosmetic and fragrance industries. The endophytes of medicinal plants participate in biochemical pathways and produce analogous or novel bioactive compounds. Panxi plateau in South-west Sichuan in China with its unique geographical and climatological characteristics is a habitat of a great variety of medicinal plants. In this study, 560 endophytic actinomycetes were isolated from 26 medicinal plant species in Panxi plateau. 60 isolates were selected for 16S rDNA-RFLP analysis and 14 representative strains were chosen for 16S rDNA sequencing. According to the phylogenetic analysis, seven isolates were Streptomyces sp., while the remainder belonged to genera Micromonospora, Oerskovia, Nonomuraea, Promicromonospora and Rhodococcus. Antimicrobial activity analysis combined with the results of amplifying genes coding for polyketide synthetase (PKS-I, PKS-II) and nonribosomal peptide synthetase (NRPS) showed that endophytic actinomycetes isolated from medicinal plants in Panxi plateau had broad-spectrum antimicrobial activity and potential natural product diversity, which further proved that endophytic actinomycetes are valuable reservoirs of novel bioactive compounds.     

Screening and characterization of endophytic fungi of Panax ginseng Meyer for biocontrol activity against ginseng pathogens

Forty endophytic fungi isolated from ginseng plants were screened to identify metabolites that had antifungal activity against ginseng microbial pathogens. The metabolites from the fungi were extracted from the liquid culture filtrates using ethyl acetate and then evaluated in vitro for antimicrobial activity against ginseng pathogens (Alternaria panax, Botrytis cinerea, Colletotrichum panacicola, Cylindrocarpon destructans, Rhizoctonia solani, and Phytophthora cactorum). Six of the fungi (Colletotrichum pisi, Fusarium oxysporum, Fusarium solani, Phoma terrestris, unknown 1 and 2) showed effective antimicrobial activity against all or some of the ginseng pathogens, with the extract of P. terrestris showing the strongest antimicrobial activity. The extract also showed inhibitory activity against spore germination of the pathogens. Gas chromatography–mass spectrometry (GC–MS) analysis of P. terrestris extract revealed that forty-one compounds were present in metabolites containing mainly N-amino-3-hydroxy-6-methoxyphthalimide (32% of the total metabolites) and 5H-dibenz [B, F] azepine (7%). Treatment with P. terrestris extract also caused morphological changes and reduced expression of the genes involved in mycelial growth and virulence. Treatment also induced defense-related genes in detached Arabidopsis leaves that were inoculated with the pathogens. These results indicate the antimicrobial potential for use of metabolites extracted from the ginseng endophytic fungi as alternatives to chemicals for biocontrol.     

Detection of polyketide synthase and nonribosomal peptide synthetase biosynthetic genes from antimicrobial coral-associated actinomycetes

The diversity and properties of actinobacteria, predominant residents in coral holobionts, have been rarely documented. In this study, we aimed to explore the species diversity, antimicrobial activities and biosynthetic potential of culturable actinomycetes within the tissues of the scleractinian corals Porites lutea, Galaxea fascicularis and Acropora millepora from the South China Sea. A total of 70 strains representing 13 families and 15 genera of actinobacteria were isolated. The antimicrobial activity and biosynthetic potential of fifteen representative filamentous actinomycetes were estimated. Crude fermentation extracts of 6 strains exhibited comparable or greater activities against Vibrio alginolyticus than ciprofloxacin. Seven of the 15 actinomycetes strains possess type I polyketide synthases (PKS-I) and/or nonribosomal peptide synthetases (NRPS) genes. Nine tested strains possess type II polyketide synthases (PKS-II). Phylogenetic analysis based on 16S rRNA gene sequences indicated that these PKS and NRPS gene screening positive strains belong to genera Nocardiopsis, Pseudonocardia, Streptomyces, Micromonospora, Amycolatopsis and Prauserella. One PKS-I and four NRPS fragments showed <70 % similarity to their closest relatives, which suggested the novelty of these genes. This study helps uncover the genetic capacity of stony coral-associated actinomycetes to produce bioactive molecules.