A PKS I gene-based screening approach for the discovery of a new polyketide from Penicillium citrinum Salicorn 46

Salicorn 46, an endophytic fungus isolated from Salicornia herbacea Torr., was identified as Penicillium citrinum based on its internal transcribed spacer and ribosomal large-subunit DNA sequences using a type I polyketide synthase (PKS I) gene screening approach. A new polyketide, penicitriketo (1), and seven known compounds, including ergone (2), (3β,5α,8α,22E)-5,8-epidioxyergosta-6,9,22-trien-3-ol (3), (3β,5α,8α,22E)-5,8-epidioxyergosta-6,22-dien-3-ol (4), stigmasta-7,22-diene-3β,5α,6α-triol (5), 3β,5α-dihydroxy-(22E,24R)-ergosta-7,22-dien-6β-yl oleate (6), N b-acetyltryptamine (7), and 2-(1-oxo-2-hydroxyethyl) furan (8), were isolated from the culture of Salicorn 46, and their chemical structures were elucidated by spectroscopic analysis. Antioxidant experiments revealed that compound 1 possessed moderate DPPH radical scavenging activity with an IC50 value of 85.33 ± 1.61 μM. Antimicrobial assays revealed that compound 2 exhibited broad-spectrum antimicrobial activity against Candida albicans, Clostridium perfringens, Mycobacterium smegmatis, and Mycobacterium phlei with minimal inhibitory concentration (MIC) values of 25.5, 25.5, 18.5, and 51.0 μM, respectively. Compound 3 displayed potent antimicrobial activities against C. perfringens and Micrococcus tetragenus with a MIC value of 23.5 μM. Compounds 5 and 6 showed high levels of selectivity toward Bacillus subtilis and M. phlei with MIC values of 22.5 and 14.4 μM, respectively. The results of this study highlight the use of PCR-based techniques for the screening of new polyketides from endophytic fungi containing PKS I genes.

Bipolamides A and B, triene amides isolated from the endophytic fungus Bipolaris sp. MU34

As a result of the continued screening for new metabolites produced by endophytic fungi from Thai medicinal plants, two new triene fatty acid amides, bipolamides A (1) and B (2), were discovered from the endophytic fungus Bipolaris sp. MU34. The structures of all of the isolated compounds were elucidated on the basis of the spectroscopic data of NMR and MS. An antimicrobial assay revealed that bipolamide B (2) had moderate antifungal activity against Cladosporium cladosporioides FERMS-9, Cladosporium cucumerinum NBRC 6370, Saccharomyces cerevisiae ATCC 9804, Aspergillus niger ATCC 6275 and Rhisopus oryzae ATCC 10404, with Minimum inhibitory concentration (MIC) values of 16, 32, 32, 64 and 64 μg ml(-1), respectively.

Bioactive metabolites from an endophytic Cryptosporiopsis sp. inhabiting Clidemia hirta

An endophytic Cryptosporiopsis sp. was isolated from Clidemia hirta and analyzed for its secondary metabolites that lead to the isolation of three bioactive molecules. The compounds were purified from the culture broth of the fungus and their structures were determined by spectroscopic methods as (R)-5-hydroxy-2-methylchroman-4-one (1), 1-(2,6-dihydroxyphenyl)pentan-1-one (2) and (Z)-1-(2-(2-butyryl-3-hydroxyphenoxy)-6-hydroxyphenyl)-3-hydroxybut-2-en-1-one (3). Compound 1 exhibited significant cytotoxic activity against the human leukemia cell line, HL-60 with an IC50 of 4 μg/ml. This compound induced G2 arrest of the HL-60 cell cycle significantly. In addition, out of these compounds, 2 and 3 were active against several bacterial pathogens. Compound 2 was active against Bacillus cereus, Escherichia coli and Staphylococcus aureus with IC50 values varying from 18 to 30 μg/ml, and compound 3 displayed activity against Pseudomonas fluorescens with an IC50 value of 6 μg/ml. Compounds 2 and 3 are novel whereas compound 1 was reported earlier but the stereochemistry of its C-2 methyl is established for the first time.

Structures and biomimetic synthesis of novel α-pyrone polyketides of an endophytic Penicillium sp. in Catharanthus roseus

Novel polyketides, citreoviripyrone A (1) and B (2), known citreomontanin (3), and (-)-citreoviridin (4) were isolated from the mycelium of the endophytic fungus. The endophytic fungus, which belongs to the genus Penicillium, was separated from surface-sterilized healthy leaves of Catharanthus roseus. The structures of 1 and 2 were determined on the basis of NMR data, and 1 was characterized as an α-pyrone polyketide featuring bicyclo[4.2.0]octadiene. The biomimetic synthesis of 1 and 2 from 3 elucidated a plausible biosynthetic pathway. Both Zn(II)-type and NAD(+)-dependent histone deacetylase inhibitors significantly enhanced the production of 1 and 3.

Flavodonfuran: a new difuranylmethane derivative from the mangrove endophytic fungus Flavodon flavus PSU-MA201

One new difuranylmethane derivative, flavodonfuran (1), together with tremulenolide A (2) was isolated from the mangrove-derived fungus Flavodon flavus PSU-MA201.The difuranylmethane derivative based on 1 is rare in natural products. Their structures were established by spectroscopic evidence. Compound 2 exhibited mild antibacterial and antifungal activities against Staphylococcus aureus ATCC25923 and Cryptococcus neoformans ATCC90113, respectively.

Endophytic fungus-vascular plant-insect interactions

Insect association with fungi has a long history. Theories dealing with the evolution of insect herbivory indicate that insects used microbes including fungi as their principal food materials before flowering plants evolved. Subtlety and the level of intricacy in the interactions between insects and fungi indicate symbiosis as the predominant ecological pattern. The nature of the symbiotic interaction that occurs between two organisms (the insect and the fungus), may be either mutualistic or parasitic, or between these two extremes. However, the triangular relationship involving three organisms, viz., an insect, a fungus, and a vascular plant is a relationship that is more complicated than what can be described as either mutualism or parasitism, and may represent facets of both. Recent research has revealed such a complex relationship in the vertically transmitted type-I endophytes living within agriculturally important grasses and the pestiferous insects that attack them. The intricacy of the association depends on the endophytic fungus-grass association and the insect present. Secondary compounds produced in the endophytic fungus-grass association can provide grasses with resistance to herbivores resulting in mutualistic relationship between the fungus and the plant that has negative consequences for herbivorous insects. The horizontally transmitted nongrass type-II endophytes are far less well studied and as such their ecological roles are not fully understood. This forum article explores the intricacy of dependence in such complex triangular relationships drawing from well-established examples from the fungi that live as endophytes in vascular plants and how they impact on the biology and evolution of free-living as well as concealed (e.g., gall-inducing, gall-inhabiting) insects. Recent developments with the inoculation of strains of type-I fungal endophytes into grasses and their commercialization are discussed, along with the possible roles the endophytic fungi play in the galls induced by the Cecidomyiidae (Diptera).

Methods for the study of endophytic microorganisms from traditional Chinese medicine plants

Plant endophytes are very numerous and widely distributed in nature, their relationships being described as a balanced symbiotic continuum ranging from mutualism through commensalism to parasitism during a long period of coevolution. Traditional Chinese medicines have played a very important role in disease treatment in China and other Asian countries. Investigations show that these medicinal plants harbor endophytes with different kinds of ecological functions, and some of them have potential to produce bioactive small-molecule compounds. This chapter will focus on the selective isolation methods, the diversity of some endophytes (actinobacteria and fungi) isolated from Traditional Chinese Medicine (TCM) plants, and the bioactive compounds from selected endophytic actinobacteria reported in the past 3 years.

Antitumor and antimicrobial activities of endophytic fungi from medicinal parts of Aquilaria sinensis

The purpose of this study was to isolate and characterize endophytic fungi from the stem tissue which can produce fragrant ingredients in Aquilaria sinensis (also called agarwood) to determine their antitumor and antimicrobial activities. Twenty-eight fungal endophytes were isolated from agarwood by strict sterile sample preparation and were classified into 14 genera and 4 taxonomic classes (Sordariomycetes, Dothideomycetes, Saccharomycetes, and Zygomycetes) based on molecular identification. Of the 28 isolates, 13 (46.4%) showed antimicrobial activity against at least one of the test strains by the agar well diffusion method, and 23 isolates (82.1%) displayed antitumor activity against at least one of five cancer cell lines by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The diameters of inhibition zones of YNAS07, YNAS14, HNAS04, HNAS05, HNAS08, and HNAS11 were equal to or higher than 14.0 mm against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, B. subtilis, Aspergillus fumigatus, and B. subtilis, respectively. The inhibition rates of YNAS06, YNAS08, and HNAS06 were not less than 60% to 293-T, 293-T, and SKVO3 cells, respectively. These results suggest that the endophytic fungi associated with agarwood will provide us with not only useful micro-ecological information, but also potential antimicrobial and antitumor agents.

Bio-control and plant growth promotion potential of siderophore producing endophytic Streptomyces from Azadirachta indica A. Juss

Three endophytic actinomycetes strains recovered from surface sterilized root tissues of Azadirachta indica A. Juss. (Meliaceae), plants were selected through tests for their potential as bio-control and plant growth promoting agents. It was also observed that the seed treated with the spore suspension of three selected strains of Streptomyces, significantly promoted plant growth and antagonized the growth of Alternaria alternata, causal agent of early blight disease in tomato plant. It was observed that the three selected strains prolifically produce IAA and siderophores that play vital role in promotion of plant growth and in suppression of Alternaria alternata. Interestingly, Streptomyces strain AzR-051 produced the highest amount of IAA at 13.73 μmol ml(-1) , compared to strains AzR-049 and AzR-010 9.22 μmol ml(-1) and 10.43 μmol ml(-1) respectively. It also produces siderophores higher than the other two strains. Thus these endophytic isolates have the potential as plant growth promoters as well as a bio-control agent, which is a useful trait for crop production in nutrient deficient soils.

Characterization of cytotoxic compound from mangrove derived fungi Irpex hydnoides VB4

OBJECTIVE

To investigate the cytotoxic activity of endophytic fungi isolated from mangrove fungi.

METHODS

In the present study the DNA was isolated and the ITS region of 5.8s rRNA was amplified using specific primers ITS 1 and ITS4 and sequence was determined using automated sequencers. Blast search sequence similarity was found against the existing non redundant nucleotide sequence database thus, identified as Aspergilus flavus, Hyporcaea lixii, Aspergillus niger, Eutorium amstelodami, Irpex hydnoides and Neurospora crassa. Among the seven isolates, one fungi Irpex hydnoides was selected for further studies. The fungi were grown in sabouraud broth for five days and filtrate were separated and subjected to ethyl acetate for further studies.

RESULTS

Nearly half (49.25%) of the extracts showed activity (IC50 of 125µg/mL). These values were within the cutoff point of the National Cancer Institute criteria for cytotoxicity (IC50<20 µg/mL) in the screening of crude plant extracts. The GC MS analysis revealed that the active principals might be Tetradecane (6.26%) with the RT 8.606.

CONCLUSIONS

It is clear from the present study that mangrove fungi with bioactive metabolites can be expected to provide high quality biological material for high throughout biochemical, anti cancer screening programmes. The results help us conclude that the potential of using metabolic engineering and post genomic approaches to isolate more novel bioactive compounds and to make their possible commercial application is not far off.

Fungal endophytes: unique plant inhabitants with great promises

Fungal endophytes residing in the internal tissues of living plants occur in almost every plant on earth from the arctic to the tropics. The endophyte-host relationship is described as a balanced symbiotic continuum ranging from mutualism through commensalism to parasitism. This overview will highlight selected aspects of endophyte diversity, host specificity, endophyte-host interaction and communication as well as regulation of secondary metabolite production with emphasis on advanced genomic methods and their role in improving our current knowledge of endophytic associations. Furthermore, the chemical potential of endophytic fungi for drug discovery will be discussed with focus on the detection of pharmaceutically valuable plant constituents as products of fungal biosynthesis. In addition, selected examples of bioactive metabolites reported in recent years (2008-2010) from fungal endophytes residing in terrestrial plants are presented grouped according to their reported biological activities.

Hidden fungi, emergent properties: endophytes and microbiomes

Endophytes are microorganisms that live within plant tissues without causing symptoms of disease. They are important components of plant microbiomes. Endophytes interact with, and overlap in function with, other core microbial groups that colonize plant tissues, e.g., mycorrhizal fungi, pathogens, epiphytes, and saprotrophs. Some fungal endophytes affect plant growth and plant responses to pathogens, herbivores, and environmental change; others produce useful or interesting secondary metabolites. Here, we focus on new techniques and approaches that can provide an integrative understanding of the role of fungal endophytes in the plant microbiome. Clavicipitaceous endophytes of grasses are not considered because they have unique properties distinct from other endophytes. Hidden from view and often overlooked, endophytes are emerging as their diversity, importance for plant growth and survival, and interactions with other organisms are revealed.

Salinosporamide natural products: Potent 20 S proteasome inhibitors as promising cancer chemotherapeutics

Proteasome inhibitors are rapidly evolving as potent treatment options in cancer therapy. One of the most promising drug candidates of this type is salinosporamide A from the bacterium Salinispora tropica. This marine natural product possesses a complex, densely functionalized γ-lactam-β-lactone pharmacophore, which is responsible for its irreversible binding to its target, the β subunit of the 20S proteasome. Salinosporamide A entered phase I clinical trials for the treatment of multiple myeloma only three years after its discovery. The strong biological activity and the challenging structure of this compound have fueled intense academic and industrial research in recent years, which has led to the development of more than ten syntheses, the elucidation of its biosynthetic pathway, and the generation of promising structure-activity relationships and oncological data. Salinosporamide A thus serves as an intriguing example of the successful interplay of modern drug discovery and biomedical research, medicinal chemistry and pharmacology, natural product synthesis and analysis, as well as biosynthesis and bioengineering.

Purification and characterization of a novel anticoagulant and fibrinolytic enzyme produced by endophytic bacterium Paenibacillus polymyxa EJS-3

INTRODUCTION

Endophytes may become a new source of thrombolytic agents for thrombosis treatment.

MATERIALS AND METHODS

A novel fibrinolytic enzyme from Paenibacillus polymyxa EJS-3 (PPFE-I) was purified with ammonium sulfate precipitation, hydrophobic chromatography, ion exchange and gel filtration chromatography. The characterization of the enzyme was investigated by means of fibrinolysis plate, hydrolysis of fibrinogen and anticoagulant effect in vitro.

RESULTS

The fibrinolytic enzyme is purified to homogeneity with a purification of 14.5 fold and a recovery of 3.3%. The enzyme was shown to have a molecular mass of 63.3kDa by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The optimum temperature and pH value were 37°C and 7.5, respectively. Results from the fibrinolysis pattern showed that the enzyme rapidly hydrolyzed the Aα-chain of fibrinogen, followed by the Bβ-chains. It also hydrolyzed the γ-chains, but more slowly. It was activated by metal ions such as Zn(2+), Mg(2+), and Fe(2+), but inhibited by Ca(2+) and Cu(2+). Furthermore, PPFE-I activity was inhibited strongly by PMSF, and it was found to exhibit a higher specificity for the synthetic substrate N-succinyl-Ala-Ala-Pro-Phe-pNA for chymotrypsin, indicating that the enzyme is a chymotrypsin-like serine protease. Additionly, PPFE-I showed a significant anticoagulant effect in vitro.

CONCLUSION

The fibrinolytic enzyme PPFE-I from endophytic bacterium Paenibacillu polymyxa EJS-3 exhibits a profound fibrinolytic activity.

Diketopiperazines produced by endophytic fungi found in association with two Asteraceae species

Diketopiperazine (DKP) derivatives, named colletopiperazine, fusaperazine C and E as well as four known DKPs were isolated from cultures of Colletotrichum gloeosporioides, Penicillium crustosum, both endophytic fungi isolated from Viguiera robusta, and a Fusarium spp., an endophyte of Viguiera arenaria, respectively. Their structures were established on the basis of their spectroscopic data. Conformational analysis of two known DKPs showed that folded conformations were as energetically stable as the extended one.

Effect of plant age on endophytic bacterial diversity of balloon flower (Platycodon grandiflorum) root and their antimicrobial activities

Balloon flower (Platycodon grandiflorum) is widely cultivated vegetable and used as a remedy for asthma in East Asia. Experiments were conducted to isolate endophytic bacteria from 1-, 3-, and 6-year-old balloon flower roots and to analyze the enzymatic, antifungal, and anti-human pathogenic activities of the potential endophytic biocontrol agents obtained. Total 120 bacterial colonies were isolated from the interior of all balloon flower roots samples. Phylogenetic analysis based on 16S rRNA gene sequences showed that the population of 'low G + C gram-positive bacteria' (LGCGPB) gradually increased 60.0-80.0% from 1 to 6 years balloon flower sample. On the other hand, maximum hydrolytic enzyme activity showing endophytic bacteria was under LGCGPB, among the bacterial strains, Bacillus sp. (BF1-1 and BF3-8), Bacillus sp. (BF1-2 and BF3-5), and Bacillus sp. (BF1-3, BF3-6, and BF6-4) showed maximum enzyme activities. Besides, Bacillus licheniformis (BF3-5 and BF6-6) and Bacillus pumilus (BF6-1) showed maximum antifungal activity against Phytophthora capsici, Fusarium oxysporum, Rhizoctonia solani, and Pythium ultimum. Moreover, Bacillus licheniformis was found in 3 and 6 years balloon flower roots, but Bacillus pumilus was found only in 6 years sample. It is presumed that older balloon flower plants invite more potential antifungal endophytes for there protection from plant diseases. In addition, Bacillus sp. (BF1-2 and BF3-5) showed maximum anti-human pathogenic activity. So, plant age is presumed to influence diversity of balloon flower endophytic bacteria.

Chemical and Functional Diversity of Natural Products from Plant Associated Endophytic Fungi

This review describes examples of naturally occurring bioactive compounds obtained from fungal endophytes from various host plants. The main topics addressed are sources, identification, biological activity, biosynthesis, and ecological and chemosystematic significance of those bioactive compounds whose sources were well defined.

Specific in situ visualization of the pathogenic endophytic fungus Aciculosporium take, the cause of witches' broom in bamboo

The endophytic fungus Aciculosporium take (Ascomycota; Clavicipitaceae) causes continuous shoot growth in bamboo. The colonized shoot eventually results in witches' broom formation but maintains normal leaf arrangement and branching pattern. To analyze the mechanism of well-regulated symptom development, the location of the fungal endophytic hyphae in host tissues was visualized. A colorimetric in situ hybridization technique using a species-specific oligonucleotide probe targeting the 18S rRNA of A. take was used. In situ hybridization was performed on tissue sections of diseased shoots with or without external signs of fungal colonization. Specific signals were detected in intercellular spaces of the bamboo tissues. Most signals were detected in the shoot apical meristem and the leaf primordia. In addition, fewer signals were detected in the lateral buds, juvenile leaves, and stems. These results indicate that A. take grows endophytically, particularly in the shoot apical meristem of the host. The location of A. take hyphae suggests that the mechanism of symptom development can be explained by the action of exogenous fungal auxin, which continuously induces primordium initiation within the host.

Importancia de los recursos genéticos de la agrobiodiversidad en el desarrollo de sistemas de producción sostenibles

Desde la óptica de la diversidad genética, Colombia es un país megadiverso con variabilidad ecosistémica importante, la cual puede ser aprovechada para el desarrollo de sistemas de producción sostenibles, eficientes y competitivos. Esto implica, aparte de la conservación de los recursos genéticos estratégicos vegetales, animales y de microorganismos, conocer el potencial de esta agrobiodiversidad para su utilización amplia, con apoyo de procesos convencionales y de la biotecnología moderna, que permitan proveer alimentos y el desarrollo del concepto integral del manejo de agroecosistemas. Por ello, en la revisión actual se incluye una descripción de la importancia de la diversidad biológica agrícola, en el nuevo contexto mundial y la necesidad de realizar procesos de conocimiento de la variabilidad y los atributos presentes en ésta, para trasladar el recurso genético de valor de existencia a los de opción y utilización.  

Recent advances in the microbial safety of fresh fruits and vegetables

Foodborne illness outbreaks linked to fresh produce are becoming more frequent and widespread. High impact outbreaks, such as that associated with spinach contaminated with Escherichia coli O157:H7, resulted in almost 200 cases of foodborne illness across North America and >$300 m market losses. Over the last decade there has been intensive research into gaining an understanding on the interactions of human pathogens with plants and how microbiological safety of fresh produce can be improved. The following review will provide an update on the food safety issues linked to fresh produce. An overview of recent foodborne illness outbreaks linked to fresh produce. The types of human pathogens encountered will be described and how they can be transferred from their normal animal or human host to fresh produce. The interaction of human pathogens with growing plants will be discussed, in addition to novel intervention methods to enhance the microbiological safety of fresh produce.