Efficient production of R-2-(4-hydroxyphenoxy) propionic acid by Beauveria bassiana using biofilm-based two-stage fermentation

In this work, a novel biofilm-based fermentation of Beauveria bassiana was employed to convert R-2- phenoxypropionic acid (R-PPA) to R-2-(4-hydroxyphenoxy) propionic acid (R-HPPA). The biofilm culture model of Beauveria bassiana produced a significantly higher R-HPPA titer than the traditional submerged fermentation method. Mannitol dosage, tryptone dosage, and initial pH were the factors that played a significant role in biofilm formation and R-HPPA synthesis. Under the optimal conditions, the maximum R-HPPA titer and productivity approached 22.2 g/L and 3.2 g/(L·d), respectively. A two-stage bioreactor combining agitation and static incubation was developed to further increase R-HPPA production. The process was optimized to achieve 100 % conversion of R-PPA, with a maximum R-HPPA titer of 50 g/L and productivity of 3.8 g/(L·d). This newly developed biofilm-based two-stage fermentation process provides a promising strategy for the industrial production of R-HPPA and related hydroxylated aromatic compounds.

Cytotoxic Drimane-Type Sesquiterpenes from Co-Culture of the Marine-Derived Fungi Aspergillus carneus KMM 4638 and Beauveria felina (=Isaria felina) KMM 4639

Chemical investigation of a coculture of the marine-derived fungi Beauveria felina KMM 4639 and Aspergillus carneus KMM 4638 led to the identification of three new drimane-type sesquiterpenes, asperflavinoids B, D and E (2, 4, 5), and nine previously reported related compounds. The structures of these compounds were established using spectroscopic methods and by comparison with known analogues. We also investigated the cytotoxic activity of the isolated compounds against several cancer and normal cell lines. Asperflavinoid C (3) and ustusolate E (9) exerted a significant effect on human breast cancer MCF-7 cell viability, with IC₅₀ values of 10 µM, and induced in caspase-dependent apoptosis and arrest of the MCF-7 cell cycle in the G2/M phase in these cells.

3-Hydroxy-4-methyldecanoic Acid-Containing Cyclotetradepsipeptides from an Endolichenic Beauveria sp

An investigation of an endolichenic Beauveria sp. led to the discovery of seven new cyclotetradepsipeptides, beauveamides A-G (2-8), along with the known beauverolide Ka (1). All incorporate a 3-hydroxy-4-methyldecanoic acid (HMDA) moiety in their structures. Their configuration was determined through Marfey's, J-based configuration analysis, and NMR computational methods, representing the first time that the stereostructures of HMDA-moiety-containing cyclotetradepsipeptides have been established. Compounds 1 and 2 exhibited protecting effects on HEI-OC1 cells at 10 μM, while 1, 4, and 5 could stimulate glucose uptake in cultured rat L6 myoblasts at 50 μM. Compound 1 showed dose-dependent activity in both L6 myoblasts and myotubes.

Secondary Metabolites with Agricultural Antagonistic Potentials from Beauveria felina, a Marine-Derived Entomopathogenic Fungus

Soil-borne pathogens and weeds could synergistically affect vegetable growth and result in serious losses. The investigation of antagonistic metabolites from a marine-derived entomopathogenic fungus, Beauveria felina, obtained polyhydroxy steroid (1), tricyclic diterpenoid (2), isaridin (3), and destruxin cyclodepsipeptides (4-6). The structures and absolute configurations of new 1-3 were elucidated by extensive spectroscopic and X-ray crystallographic analyses, as well as electronic circular dichroism (ECD) calculations. Compounds 1 and 2 showed antifungal activities against carbendazim-resistant strains of Botrytis cinerea, with the minimum inhibitory concentration (MIC) values ranging from 16 to 32 μg/mL, which were significantly better than those of carbendazim (MIC = 256 μg/mL). Compound 5 exhibited significant antagonistic activity against the radicle growth of Amaranthus retroflexus seedlings, which was almost identical to that of the positive control (2,4-dichlorophenoxyacetic acid). The structure-activity differences of 4-6 suggested that the Cl atom in HMPA¹ and β-Me in Pro² should be the key factors to their herbicidal activities. Besides, compounds 3-6 showed moderate nematicidal activities against Meloidogyne incognita. These antagonistic effects of 1-6 were first reported and further revealed the synergistically antagonistic potential of B. felina to be developed into the biopesticide.

Siderophores from the Entomopathogenic Fungus Beauveria bassiana

We report NMR- and MS-based structural characterizations of siderophores and related compounds from Beauveria bassiana (Balsamo-Crivelli) Vuillemin, including ten new chemical entities (2-4, 6-9, 11-12, and 15) and five known compounds, (1, 5, 10, 13, and 14). The siderophore mixture from ARSEF strain #2680 included two compounds in which N⁵-mevalonyl-N⁵-hydroxyornithine replaces both (2) or one (3) of the N⁵-anhydromevalonyl-N⁵-hydroxyornithine units of dimerumic acid (1). Mevalonolactone (14) was present as a degradation product of 2 and 3. ARSEF #2860 also produced compounds that have mannopyranose (5, 6) or 4-O-methyl-mannopyranose units (4, 7), two compounds (8, 9) that can be rationalized as 4-O-methyl-mannopyranosyl analogues of the esterifying acid moieties of metachelins A and B, respectively, and two probable decomposition products of 1, a nitro compound (11) and a formate (12). Beauverichelin A (15), a coprogen-type siderophore that represents the di-4-O-methyl-mannopyranosyl analogue of metachelin A, was detected in crude extracts of ARSEF #2860, but only in trace amounts. ARSEF strains #252 and #1955 yielded beauverichelin A in quantities that were sufficient for NMR analysis. Only the di- (1-7) and trihydroxamate (15) siderophores showed iron-binding activity in the CAS assay and, when ferrated, showed strong ESIMS signals consistent with 1:1 ligand/iron complexes.

The Inhibitory Effects of Cyclodepsipeptides from the Entomopathogenic Fungus Beauveria bassiana on Myofibroblast Differentiation in A549 Alveolar Epithelial Cells

Pulmonary fibrosis (PF) is a chronic and fatal lung disease with few treatment options. Although the pathogenesis of PF is not clear, a chronic inflammatory response to continuous damage is considered the cause of pulmonary fibrosis. PF is characterized by excessive accumulation of extracellular matrix (ECM), therefore, inhibition of myofibroblast differentiation is a good therapeutic target for PF. As part of our continuing endeavor to explore biologically active metabolites from insect-associated microbes, we found that the MeOH extract of the culture broth from the entomopathogenic fungus Beauveria bassiana inhibited collagen induction and E-cadherin down-regulation. In order to identify active compounds, we carried out chemical analysis of the MeOH extract with the assistance of LC/MS-guided isolation approach, which led to the successful identification of four cyclodepsipeptides 1–4. Among the isolates, compound 2 showed inhibitory effects on myofibroblast differentiation induced by TGF-β1. Compound 2 inhibited induction of α-SMA and N-cadherin, which are myofibroblast markers, and blocked the accumulation of ECM proteins such as collagen and fibronectin. Overall these findings demonstrate that compound 2 can be used to attenuate pulmonary fibrosis by targeting myo- fibroblast differentiation.

The effect of entomopathogenic fungal culture filtrate on the immune response and haemolymph proteome of the large pine weevil, Hylobius abietis

The large pine weevil Hylobius abietis L. is a major forestry pest in 15 European countries, where it is a threat to 3.4 million hectares of forest. A cellular and proteomic analysis of the effect of culture filtrate of three entomopathogenic fungi (EPF) species on the immune system of H. abietis was performed. Injection with Metarhizium brunneum or Beauvaria bassiana culture filtrate facilitated a significantly increased yeast cell proliferation in larvae. Larvae co-injected with either Beauvaria caledonica or B. bassiana culture filtrate and Candida albicans showed significantly increased mortality. Together these results suggest that EPF culture filtrate has the potential to modulate the insect immune system allowing a subsequent pathogen to proliferate. Injection with EPF culture filtrate was shown to alter the abundance of protease inhibitors, detoxifing enzymes, antimicrobial peptides and proteins involved in reception/detection and development in H. abietis larvae. Larvae injected with B. caledonica culture filtrate displayed significant alterations in abundance of proteins involved in cellulolytic and other metabolic processes in their haemolymph proteome. Screening EPF for their ability to modulate the insect immune response represents a means of assessing EPF for use as biocontrol agents, particularly if the goal is to use them in combination with other control agents.

Study of a New Biological Control Method Combining an Enteropathogen and a Chemical Insecticide Against Solenopsis invicta (Hymenoptera: Formicidae)

Solenopsis invicta (Buren; Hymenoptera: Formicidae) is a species that has invaded China in recent years. Currently, S. invicta is mainly controlled by chemical treatment, though long-term use of chemical pesticides can cause serious environmental pollution. In this study, a microbial insecticide formulated for the control of S. invicta was screened for laboratory toxicity and field efficacy. The co-toxicity coefficients (CTCs) of the combination of Beauveria bassiana and thiacloprid at various mass ratios were 356.53, 251.20, 182.50, 215.03, and 143.19. When B. bassiana powder and thiacloprid were mixed at a mass ratio of 8:2, the CTC was 356.53, demonstrating a very significant synergistic effect. According to a field efficacy test, at 3 d after treatment, the efficacy of mound injection was significantly better than that of mound drenching. In this study, the insecticidal activity of pathogenic microorganisms against S. invicta was markedly enhanced by using a self-designed apparatus for mound injection of the tested preparation of a complex containing a pathogenic microbe. The results show that S. invicta can be sustainably controlled while ensuring the safety of the environment. The findings are a good reference for the promotion and application of safe control of S. invicta in the future.

Synthesis and Bioconversion of Curcumin Analogs

Hydrogdnation of curcumin (1), a chemopreventive agent from Turmeric (Curcuma longa L.) yielded three major compounds: 1,7-bis(4-hydroxy-3- methoxyphenyl)heptane-3,5-dione (2), 5-hydroxy-1,7-bis(4-hydroxy-3-methoxyphenyl)heptan-3-one (3), and 1,7-bis(4-hydroxy-3-methoxyphenyl)heptane- 3,5-diol (4). Incubation of compound (2) with Beauveria bassiana ATCC 7159 afforded the hexahydrocurcumin (3) as the sole metabolite while biotransformation.of curcumin (1) with B. bassiana gave metabolites 2-4 along with the curcumin-4'-0-4"'-O-methyl-β-D-glucopyranoside (5) and octahydrocurcumih-4'-O-4"'-O-methyl--β-D-glucopyranoside (6). The bioconversion of curcumin (1) with Rhizopus oryzae ATCC 11145 yielded analogs 2-4 while no transformation of curcumin (1) was observed with Aspergillus niger ATCC 16888. The preparation, structural elucidation and biological activities of these metabolites are reported herein.

Development of a CO2 -releasing coformulation based on starch, Saccharomyces cerevisiae and Beauveria bassiana attractive towards western corn rootworm larvae

BACKGROUND

CO₂ is known as an attractant for many soil-dwelling pests. To implement an attract-and-kill strategy for soil pest control, CO₂ -emitting formulations need to be developed. The aim of the present work was to develop a slow-release bead system in order to bridge the gap between application and hatching of western corn rootworm larvae.

RESULTS

We compared different Ca-alginate beads containing Saccharomyces cerevisiae for their potential to release CO₂ over a period of several weeks. The addition of starch improved CO₂ release, resulting in significantly higher CO₂ concentrations in soil for at least 4 weeks. The missing amylase activity was compensated for either by microorganisms present in the soil or by coencapsulation of Beauveria bassiana. Formulations containing S. cerevisiae, starch and B. bassiana were attractive for western corn rootworm larvae within the first 4 h following exposure; however, when considering the whole testing period, the maize root systems remained more attractive for the larvae.

CONCLUSION

Coencapsulation of S. cerevisiae, starch and B. bassiana is a promising approach for the development of attractive formulations for soil applications. For biological control strategies, the attractiveness needs to be increased by phagostimuli to extend contact between larvae and the entomopathogenic fungus growing out of these formulations. © 2016 Society of Chemical Industry.

Subcellular localization of five singular WSC domain-containing proteins and their roles in Beauveria bassiana responses to stress cues and metal ions

Some model fungi have three or four proteins with each vectoring a single cell Wall Stress-responsive Component (WSC) domain at N-terminus. In this study, five proteins, each vectoring only a single WSC domain in N-terminal, central or even C-terminal region, were found in Beauveria bassiana, a filamentous fungal entomopathogen, and named Wsc1A-1E due to the domain singularity. Four of them lack either transmembrane domain or C-terminal conserved signature sequence (DXXD) compared with the homologues in the model fungi. Intriguingly, all the eGFP-tagged fusion proteins of Wsc1A-1E were evidently localized to the cell wall and membrane of transgenic hyphae. Single deletions of the five wsc genes resulted in significant, but differential, increases in cellular sensitivity to cell wall perturbation, oxidation, high osmolarity, and four to six metal ions (Zn(2+) , Mg(2+) , Fe(2+) , K(+) , Ca(2+) and Mn(2+) ). Each deletion mutant also showed a delay of germination and a decrease of conidial UV-B resistance, thermotolerance or both. However, none of the deletions affected substantially the fungal growth, conidiation and virulence. Our results indicate a significance of each WSC protein for the B. bassiana adaptation to diverse habitats of host insects.

Citrifelins A and B, Citrinin Adducts with a Tetracyclic Framework from Cocultures of Marine-Derived Isolates of Penicillium citrinum and Beauveria felina

Citrifelins A (1) and B (2), two citrinin adducts possessing a unique tetracyclic framework, were characterized from a coculture of marine-derived fungal isolates of Penicillium citrinum and Beauveria felina. Neither fungus produced these compounds when cultured alone under the same conditions. The structures of these adducts were elucidated on the basis of spectroscopic analysis, and the absolute configurations were assigned on the basis of TDDFT-ECD calculations. A hypothesis that adducts 1 and 2 might be derived from a citrinin derivative through a non-pericyclic Michael reaction is proposed. Compounds 1, 2, and 5 showed inhibitory activities against several human and aquatic pathogens.

Cyclohexadepsipeptides of the isaridin class from the marine-derived fungus Beauveria felina EN-135

Three new cyclohexadepsipeptides of the isaridin class including isaridin G (1), desmethylisaridin G (2), and desmethylisaridin C1 (3), along with three related known metabolites (4-6), were isolated and identified from the marine bryozoan-derived fungus Beauveria felina EN-135. The structures of these compounds were elucidated on the basis of extensive spectroscopic analysis, and the structures and absolute configurations of compounds 1-3 were confirmed by single-crystal X-ray diffraction analysis. The crystal structures showed the presence of β-turns for the Tyr(3)/N-Me-Val(4) and Phe(3)/N-Me-Val(4) amide bonds in compounds 2 and 3, respectively, in the cis conformations, which were opposite other reported isaridins. The conformations of the HMPA(1)-Pro(2) amide bond in compound 2 are different in the solution and in the crystal structures, which showed trans and cis geometries, respectively, while compounds 1 and 3 do not exhibit this phenomenon. Each of the isolated compounds was evaluated for antimicrobial activity and brine shrimp lethality. Compound 3 exhibited antibacterial activity against E. coli with an MIC value of 8 μg/mL.

Suberoylanilide hydroxamic acid, a histone deacetylase inhibitor, induces the production of anti-inflammatory cyclodepsipeptides from Beauveria felina

The addition of the histone deacetylase inhibitor suberoylanilide hydroxamic acid to a culture of the filamentous fungus Beauveria felina significantly changed its secondary metabolite profile and led to the isolation of eight compounds, including three new cyclodepsipeptides, desmethylisaridin E (1), desmethylisaridin C2 (2), and isaridin F (3), along with five known cyclodepsipeptide compounds. Isaridin F (3) possesses a cyclodepsipeptide ring with N-methylbutyric acid, which is rare in natural peptides. Absolute configurations of the new cyclodepsipeptides were achieved by Marfey's method. The anti-inflammatory activity of the isolated compounds was investigated through evaluating their effect on superoxide anion production and elastase release by FMLP-induced human neutrophils. Among the tested compounds, desmethylisaridin E (1) inhibited superoxide anion production and desmethylisaridin C2 (2) inhibited elastase release, with IC50 values of 10.00 ± 0.80 and 10.01 ± 0.46 μM, respectively.

[Antioxidation and multidrug resistance of structure-similar ATP-binding cassette transporter proteins in two fungal entomopathogens]

OBJECTIVE

Structure-similar ATP-binding cassette (ABC) transporter proteins, BbT1 in Beauveria bassiana (Bb) and IfT1 in Isaria fumosorosea (If), were characterized.

METHODS

Various phenotypes including cellular antioxidant response, multidrug resistance and virulence were compared between wild-type strain and the constructed mutants DeltaBbT1, DeltaBbT1/BbT1 and DBbT1/IfT1.

RESULTS

Compared with the wild-type, DeltaBbT1/BbT1 and DeltaBbT1/ IfT1 strains showing no significant changes in examined phenotypes, DeltaBbT1 became 27% to 2.1-fold less tolerant to the oxidative stress of 20-40 mmol/L H2O2 and 2-8 mmol/L menadione, 28% to 4.7-fold less resistant to carbendazim, itraconazole, dimetachlone, cycloheximide, ethirimol and 4-nitroquinoline N-oxide, and about 20% less virulent to the second-instar larvae of Spodoptera litura.

CONCLUSION

The ABC transporter proteins BbT1 and IfT1 are similar not only in sequence structure but also in biological function, act as one of the determinants for the multidrug resistance of Bb and If, and also contribute to the fungal virulence due to involvement in cellular antioxidant response.

Recognition of a core fragment ofBeauveria bassiana hydrophobin gene promoter (P hyd1) and its special use in improving fungal biocontrol potential

To identify a suitable promoter for use in engineering fungal entomopathogens to improve heterologous gene expression and fungal biocontrol potential, a 1798 bp promoter (P hyd1) upstream of Beauveria bassiana class I hydrophobin gene (hyd1) was optimized by upstream truncation and site-directed mutation. A truncated 1290 bp fragment (P hyd1-t1) drove eGFP expression in B. bassiana much more efficiently than full-length P hyd1. Further truncating P hyd1-t1 to 1179, 991 and 791 bp or mutating one of the binding domains of three transcription factors in P hyd1-t1 reduced significantly the expression of eGFP (enhanced green fluorescence protein). Under P hyd1-t1 control, eGFP was expressed more abundantly in conidiogenic cells and conidia than in mycelia. Therefore, P hyd1-t1 was used to integrate a bacterium-derived, insect midgut-specific toxin (vip3Aa1) gene into B. bassiana, yielding a transgenic strain (BbHV8) expressing 9.8-fold more toxin molecules in conidia than a counterpart strain (BbV28) expressing the toxin under the control of P gpdA, a promoter widely used for gene expression in fungi. Consequently, BbHV8 showed much higher per os virulence to Spodoptera litura larvae than BbV28 in standardized bioassays with normal conidia for both cuticle penetration and ingestion or heat-killed conidia for ingestion only. Conclusively, P hyd1-t1 is a useful tool for enhancing beneficial protein expression, such as vip3Aa1, in fungal conidia, which are the active ingredients of mycoinsecticides.

Study of the rheological properties of a fermentation broth of the fungus Beauveria bassiana in a bioreactor under different hydrodynamic conditions

Fermentation with filamentous fungi in a bioreactor is a complex dynamic process that is affected by flow conditions and the evolution of the rheological properties of the medium. These properties are mainly affected by the biomass concentration and the morphology of the fungus. In this work, the rheological properties of a fermentation with the fungus Beauveria bassiana under different hydrodynamic conditions were studied and the rheological behavior of this broth was simulated through a mixture of carboxymethyl cellulose sodium and cellulose fibers (CMCNa-SF). The bioreactor was a 10 L CSTR tank operated at different stir velocities. Rheological results were similar at 100 and 300 rpm for both systems. However, there was a significant increase in the viscosity accompanied by a change in the consistence index, calculated according to the power law model, for both systems at 800 rpm. The systems exhibited shear-thinning behavior at all stir velocities, which was determined with the power law model. The mixing time was observed to increase as the cellulose content in the system increased and, consequently, the efficiency of mixing diminished. These results are thought to be due to the rheological and morphological similarities of the two fungal systems. These results will help in the optimization of scale-up production of these fungi.

A novel protease inhibitor in Bombyx mori is involved in defense against Beauveria bassiana

Entomopathogenic fungi, such as Beauveria bassiana, penetrate the insect cuticle using a plethora of hydrolytic enzymes including cuticle-degrading proteases and chitinases, which are important virulence factors. The insect integument and hemolymph contains a relatively high concentration of protease inhibitors, which are closely involved with defense against pathogenic microorganisms. To elucidate the molecular mechanism underlying resistance against entomopathogenic fungi and to identify a new molecular target for improving fungal resistance in the silkworm, Bombyx mori, we cloned and expressed a novel silkworm TIL-type protease inhibitor BmSPI38, which was very stable over a wide range of temperatures and pH values. An activity assay suggested that BmSPI38 potently inactivated the insecticidal cuticle-degrading enzyme (CDEP-1) produced by B. bassiana and subtilisin A produced by Bacillus licheniformis. The melanization of silkworm induced by CDEP-1 protease could also be blocked by BmSPI38. These results provided new insights into the molecular mechanisms whereby insect protease inhibitors provide resistance against entomopathogenic fungi, suggesting the possibility of using fungal biopesticides in sericulture.

Insecticidal cyclodepsipeptides from Beauveria felina

A novel cyclodepsipeptide, iso-isariin B (1), and the known isaridin E (2) were isolated from the entomopathogenic fungus Beauveria felina. Their structures were elucidated using MS/MS fragmentation and extensive 2D-heteronuclear NMR. The X-ray structure of isaridin E was obtained, showing two potent intramolecular H bonds and a type-VI turn with the HyLeu(1)-Pro(2) amide bond in a cis conformation. Iso-isariin B (1) was active against the pest-insect Sitophilus spp. with an LD(50) value of 10 μg/mL. This observation also gives some clues for ecological interpretation of cyclodepsipeptide production by B. felina.

Application of the Beauveria bassiana strain for the enantioselective oxidation of the diethyl 1-hydroxy-1-phenylmethanephosphonate

Biotransformation of diethyl 1-hydroxy-1-phenylmethanephosphonate using fungi Beauveria bassiana allowed resolving the racemic mixture of the substrate and due to the biocatalyst and reaction conditions modifications, leading to desired optical isomer.

Relation of aphicidal activity with cuticular degradation by Beauveria bassiana SFB-205 supernatant incorporated with polyoxyethylene-(3)-isotridecyl ether

The application of Beauveria bassiana SFB-205 supernatant incorporated with polyoxyethylene-(3)-isotridecyl ether (TDE-3) significantly reduced the population of two species of aphids including cotton aphid, Aphis gossypii, and green peach aphid, Myzus persicae, much higher in cotton aphid, compared with supernatant incorporated with Tween 80, which allows the relationship of aphicidal activity with the degradation of aphid cuticles to be determined. Overall, the degradation of the cuticles induced by the supernatant was more remarkable in conjunction with TDE-3 than Tween 80, and this phenomenon was more observable in cotton aphid through SDS-polyacrylamide gel electrophoresis, revealing high correlation with their aphicidal activities.

Influence of fungal odor on grooming behavior of the termite, Coptotermes formosanus

The termite Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) protects itself from entomopathogenic fungus by mutual grooming behavior. C. formosanus removes foreign organisms, such as fungal conidia, from the body surface of its nestmates by mutual grooming behavior and eating them. The conidia removal rate from the body surface differed according to the isolate of entomopathogenic fungi (Beauveria brongniartii 782, Paecilomyces fumosoroseus K3, and Metarhizium anisopliae 455), and the removal rate of the fungal isolates seemed to depend on feeding preference, which was determined using paper discs moistened with a fungal suspension. In addition, it was found that C. formosanus without antennae groomed their nestmates more frequently than those with antennae. Consequently, it seems that C. formosanus antennae detect substances without touching, such as via odor, and it affects the efficiency of grooming behavior. The results of single sensillum recording support the hypothesis that C. formosanus are capable of distinguishing three species of fungi by their odors.

[Organisms producing hypolipidemic compounds with antioxidant activity]

Complex compounds produced by fungal cultures of Lecanicilium and Beauveria with both high hypolipidemic and antioxydant activities were screened. Two fractions of the hypolipipidemic compounds with antioxidant activity of 95 and 75% in a dose of 25 mcg/ml were isolated.

[Isolation and identification of toxins inhibiting Dentrolimus tabulaeformis from an antagonistic strain of Beauveria]

OBJECTIVE

We used submerged fermentation to cultivate a strain of the entomopathogenic fungus Beauveria tenella isolated from the infected larvae of Dentrolimus tabulaeformis in Pinus tabulaeformis forest in Chengde of Hebei Province in China.

METHODS

We used ethyl acetate to extract antagonistic components from the fermentation broth and used silica gel column chromatography and GC/MS to separate and identify the components.

RESULTS

Six compounds were obtained by silica gel column chromatography. The sixth compound had higher activity to kill the larvae of Dentrolimus tabulaeformis with a corrected mortality rate of 80%. Seventeen compounds were separated and identified by GC/MS in the 6th group, of which 3compounds were more than 10%, 2-Piperidinone (14.02%), 2-coumaranone (47.10%), and Pyrrolo[1,2-a]Pyrazine-1,4-dione, hexahydro (21.05%).

CONCLUSION

2-Piperidinone and 2-coumaranone had insecticidal activity (corrected mortality rate reached 83.32% and 91.61% respectively) and were the most important toxic substances to control pests.

Volatile organic compounds released by the entomopathogenic fungus Beauveria bassiana

The composition of volatile organic compounds (VOC) released by the entomopathogenic fungus Beauveria bassiana (Hyphomycete: Deuteromycotina) utilizing two different carbon sources was investigated. Analyses were performed by solid-phase microextraction (SPME) coupled to capillary gas chromatography (CGC) and CGC-mass spectrometry (MS). Major components in glucose-grown cultures were diisopropyl naphthalenes, ethanol, and sesquiterpenes. Alkane-grown fungal VOC switched to a fingerprint with prevalence of n-decane. This is the first report on the volatiles released by entomopathogenic fungi.

Surface characteristics of the entomopathogenic fungus Beauveria (Cordyceps) bassiana

Marked differences in surface characteristics were observed among three types of single-cell propagules produced by the entomopathogenic fungus Beauveria bassiana. Atomic force microscopy (AFM) revealed the presence of bundles or fascicles in aerial conidia absent from in vitro blastospores and submerged conidia. Contact angle measurements using polar and apolar test liquids placed on cell layers were used to calculate surface tension values and the free energies of interaction of the cell types with surfaces. These analyses indicated that the cell surfaces of aerial conidia were hydrophobic, whereas those of blastospores and submerged conidia were hydrophilic. Zeta potential determinations of the electrostatic charge distribution across the surface of the cells varied from +22 to -30 mV for 16-day aerial conidia at pH values ranging from 3 to 9, while the net surface charge ranged from +10 to -13 mV for submerged conidia, with much less variation observed for blastospores, +4 to -4 mV, over the same pH range. Measurements of hydrophobicity using microbial adhesion to hydrocarbons (MATH) indicated that the surfaces of aerial conidia were hydrophobic, and those of blastospores hydrophilic, whereas submerged conidia displayed cell surface characteristics on the borderline between hydrophobic and hydrophilic. Insect pathology assays using tobacco budworm (Heliothis virescens) larvae revealed some variation in virulence among aerial conidia, in vitro blastospores and submerged conidia, using both topical application and haemocoel injection of the fungal cells.

Phage display cDNA cloning and expression analysis of hydrophobins from the entomopathogenic fungus Beauveria (Cordyceps) bassiana

Hydrophobins are small amphipathic proteins that function in a broad range of growth and developmental processes in fungi. They are involved in the formation of aerial structures, the attachment of fungal cells to surfaces, and act in signalling in response to surface cues and pathogenesis. Beauveria bassiana is an important entomopathogenic fungus used as an arthropod biological control agent. To examine the feasibility of using phage display technology to clone cDNAs encoding hydrophobins, biopanning experiments were performed using a variety of affinity resins, including N,N'-diacetylchitobiose-, fucose-, lactose-, maltose- and melibiose-coupled agarose beads. After five rounds of iterative biopanning, cDNAs corresponding to two B. bassiana (class I) hydrophobins were selectively enriched using melibiose- or lactose-coupled agarose beads. Expression analysis revealed that the hyd1 gene was expressed in all samples tested, including aerial conidia, in vitro blastospores, submerged conidia, and cells sporulating on chitin and insect cuticle, with hyd1 expression peaking in growing mycelia. In contrast, the hyd2 gene was not appreciably expressed in any of the single-cell types (aerial conidia, blastospores and submerged conidia), but was constitutively expressed in growing mycelia and when cells were sporulating on chitin and insect cuticle. MS fingerprinting of an approximately 10 kDa protein found in boiling SDS-insoluble, trifluoroacetic acid-soluble extracts from aerial conidia identified the major component of the B. bassiana rodlet layer to be the hyd2 gene product. These results reveal the differential regulation of the isolated hydrophobins and indicate that phage display represents a novel approach to cDNA cloning of hydrophobins.

Cytotoxic and Antihaptotactic beauvericin analogues from precursor-directed biosynthesis with the insect pathogen Beauveria bassiana ATCC 7159

Precursor-directed biosynthesis was used to produce analogues of the cyclic depsipeptide mycotoxin beauvericin (1) using the filamentous fungus Beauveria bassiana ATCC 7159. Feeding 30 analogues of D-2-hydroxyisovalerate and L-phenylalanine, the natural 2-hydroxycarboxylic acid and amino acid precursors of beauvericin, led to the biosynthesis of novel beauvericins. Six of these were isolated and characterized, and their cytotoxicity and directional cell migration (haptotaxis) inhibitory activity against the metastatic prostate cancer cell line PC-3M were evaluated. Replacement of one, two, or all three of the D-2-hydroxyisovalerate constituents in beauvericin (1) with 2-hydroxybutyrate moieties (beauvericins G(1-3), compounds 2-4) caused a parallel decline of cell migration inhibitory activity and cytotoxicity, suggesting a requirement for a branched side chain for both of these biological activities at the corresponding positions of beauvericins. Replacement of one, two, or all three N-methyl-L-phenylalanine residues of beauvericin with N-methyl-L-3-fluorophenylalanine moieties (beauvericins H(1-3), compounds 5-7) increased cytotoxicity without affecting antihaptotactic activity.

New destruxins from the marine-derived fungus Beauveria felina

Chemical investigation of the cytotoxic and anti-tuberculosis active butanone extract obtained from the growth media of the marine-derived fungus Beauveria felina led to the isolation of two new destruxins, [beta-Me-Pro] destruxin E chlorohydrin (1) and pseudodestruxin C (3), along with five known cyclic depsipeptides. The structures of the new destruxin derivatives were established by analysis of spectroscopic data, while the absolute configuration of the common amino acid residues was established by Marfey's analysis. The absolute configuration of the 2(R),4(S)-5-chloro-2,4-dihydroxypentanoic acid residue in 1 could be established by application of a J-based configuration method followed by derivatization with R-MPA-Cl and NMR analysis.

[Evaluation for enhanced aphidicidal activity of a noval emulsifiable formulation of Beauveria bassiana conidia]

A noval emulsifiable formulation (EF) of Beauveria bassiana SG8702 containing 10(10) conidia/mL was prepared by suspending dry conidia in mineral oil-based liquid containing emulsifier, stabilizer and UV protectant (emulsion), and then bioassayed on newly merged adults of the green peach aphid, Myzus percisae, in parallel to the unformulated conidia (UC). For inoculation, five gradient concentrations of aqueous EF and UC suspensions (5 x 10(5) - 1 x 10(8) conidia/mL) were separately sprayed on to aphids on detached cabbage leaves (30 - 40 adults/leaf) using a Micro Ulva hand-held sprayer, generating EF dosages of 1.5, 6.3, 32.6, 87.6 and 701.1 conidia/mm2, and UC dosages of 2.8, 9.2, 52.7, 114.8 and 1005.9 conidia/mm2, respectively. All dosage treatments including controls for EF (100-fold dilution of the emulsion) and UC (water spray) were replicated three times (aphid colonies on three leaves), and maintained in Petri dishes at 23 degrees C and 12 : 12 (L: D) for 8-day daily records. Cadavers, whenever found, were moved into a moist chamber to facilitate fungal outgrowths for verification of B. bassiana infection. The resulting data fit very well to time-dose-mortality model with EF having a larger dose effect (1.05 +/- 0.10) than UC (0.82 +/- 0.11) and also faster time effect. The estimates of the dose- and time-effect parameters were then used to compute lethal concentrations (LC50) and time lengths (LT50). The estimates of LC50 with 95% confidence intervals for both EF and UC were 9.0 (6.9 - 11.6) and 634 (263 - 1532) conidia/mm2 on day 4 after spray, and 3.3 (2.4 - 4.6) and 5.3 (3.2 - 8.6) on day 7, apparently decreasing with increasing time lengths after spray. The estimates of LT50 for EF and UC were 4.9 d and 7.2 d at 5 conidia/mm2, 4.0 d and 5.6 d at 10 conidia/mm2, and 3.2 d and 4.5 d at 100 conidia/mm2, indicating a trend of decrease with increasing counts of conidia attached to the leaves. The results indicate that the emulsifiable formulation of B. bassiana conidia had greater aphidicidal activity than the unformulated conidia. Finally, problems with evaluation of mycoinsecticides and other microbial formulations are discussed and technical standards are recommended.