Effect of entomopathogenic fungus Beauveria bassiana on the growth characteristics and metabolism of black soldier fly larvae

Beauveria bassiana is an entomopathogenic fungus widely used in agriculture to reduce populations of various pests. However, when agricultural waste is utilized for organic recycling, B. bassiana has the potential to impact recycling performance, by affecting the survival, and body mass of decomposing organisms (such as insect's larvae). Additionally, in natural conditions where decayed organic matter contains a high load of different entomopathogenic organisms, larval growth may be affected when consumed or in contact. In a laboratory study, we aimed to comprehend the effects of B. bassiana on the growth characteristics and larval metabolism of the black soldier fly larvae, which is a known decomposing insect. The experiments used both feeding (mixing the spores with the diet, hereafter BF) and contact treatments (by dipping the larva in the spores solution, hereafter BD), and were compared to a water-treated control group. The BF treatment significantly reduced larval body weight, adult emergence, and adult weight compared to both the control and the BD treatment. Furthermore, an analysis of hemolymph metabolites, categorized by class, indicated a higher accumulation of metabolites belonging to the purine and purine derivative classes, as well as carboxylic acids and their derivatives, including peptides and oligopeptides, indicating potential disruption of protein synthesis or degradation caused by the BF treatment. Pathway enrichment analysis showed significant alterations in purine metabolism and D-Arginine and D-ornithine metabolism compared to the control. Taurine and hypotaurine metabolism were significantly altered in the BD treatment compared to the control but not significantly enriched in the BF treatment. Our results suggest that the BF treatment impairs protein synthesis or degradation, affecting larval growth characteristics. Future studies should explore innate immunity-related gene expression and antimicrobial peptide production in BSF larvae to understand their immunity to pathogens.

Ecosystem services of entomopathogenic ascomycetes

Entomopathogenic ascomycetes (EA) are an important part of the microbiota in most terrestrial ecosystems, where they can be found regulating natural populations of arthropod pests in both epigeous and hypogeous habitats while also establishing unique relationships with plants. These fungi offer direct benefits to agriculture and human welfare. In the present work, we conducted a systematic review to comprehensively assess the range of ecosystem services provided by EA, including direct and indirect pest biocontrol, plant growth promotion, plant defense against other biotic and abiotic stresses, nutrient cycling, and the production of new bioactive compounds with agricultural, pharmaceutical and medical importance. Moreover, EA are compatible with the ecosystem services provided by other microbial and macrobial biocontrol agents. This systematic review identified the need for future research to focus on evaluating the economic value of the ecological services provided by EA with a special emphasis on hypocrealean fungi. This evaluation is essential not only for the conservation but also for better regulation and exploitation of the benefits of EA in promoting agricultural sustainability, reducing the use of chemicals that enter the environment, and minimizing the negative impacts of crop protection on the carbon footprint and human health.

Preliminary Analysis of Transcriptome Response of Dioryctria sylvestrella (Lepidoptera: Pyralidae) Larvae Infected with Beauveria bassiana under Short-Term Starvation

The Dioryctria genus contains several destructive borer pests that are found in coniferous forests in the Northern Hemisphere. Beauveria bassiana spore powder was tested as a new method of pest control. In this study, Dioryctria sylvestrella (Lepidoptera: Pyralidae) was used as the object. A transcriptome analysis was performed on a freshly caught group, a fasting treatment control group, and a treatment group inoculated with a wild B. bassiana strain, SBM-03. Under the conditions of 72-h fasting and a low temperature of 16 ± 1 °C, (i) in the control group, 13,135 of 16,969 genes were downregulated. However, in the treatment group, 14,558 of 16,665 genes were upregulated. (ii) In the control group, the expression of most genes in the upstream and midstream of the Toll and IMD pathways was downregulated, but 13 of the 21 antimicrobial peptides were still upregulated. In the treatment group, the gene expression of almost all antimicrobial peptides was increased. Several AMPs, including cecropin, gloverin, and gallerimycin, may have a specific inhibitory effect on B. bassiana. (iii) In the treatment group, one gene in the glutathione S-transferase system and four genes in the cytochrome P450 enzyme family were upregulated, with a sharp rise in those that were upregulated significantly. In addition, most genes of the peroxidase and catalase families, but none of the superoxide dismutase family were upregulated significantly. Through innovative fasting and lower temperature control, we have a certain understanding of the specific defense mechanism by which D. sylvestrella larvae may resist B. bassiana in the pre-wintering period. This study paves the way for improving the toxicity of B. bassiana to Dioryctria spp.

Prospective of mycorrhiza and Beauvaria bassiana silica nanoparticles on Gossypium hirsutum L. plants as biocontrol agent against cotton leafworm, Spodoptera littoralis

BACKGROUND

Plant-herbivorous insects are a severe danger to the world's agricultural production of various crops. Insecticides used indiscriminately resulted in habitat destruction due to their high toxicity, as well as disease resistance. In this respect, the development of a sustainable approach to supreme crop production with the least damage is a crucially prerequisite. As a result, the current study was carried out to understand the potential effect of arbuscular mycorrhizal (AM) fungi along with Beauvaria bassiana silica nanoparticles (Si NPs) as a new approach to increase cotton (Gossypium hirsutum L. Merr.) defense against an insect herbivore, Spodoptera littoralis. AM and non-AM cotton plants were infested with S. littoralis and then sprayed with a biopesticide [B. bassiana Si NPs] or a chemical insecticide (Chlorpyrifos).

RESULTS

The gas chromatography-mass spectrometry (GC-MS) analysis of B. bassiana Si NPs fungal extract showed that the major constituents identified were Oleyl alcohol, trifluoroacetate, 11-Dodecen-1-AL and 13-Octadecenal, (Z)-(CAS). Besides, results revealed a highly significant decrease in growth parameters in S. littoralis infested plants, however, with AM fungal inoculation a substantial improvement in growth traits and biochemical parameters such as protein and carbohydrates contents was observed. In addition, stimulation in proline and antioxidant enzymes activity and a decrease in malondialdehyde content were observed after AM inoculation.

CONCLUSION

AM fungi mitigate the harmful effects of herbivorous insects by strengthening the cotton plant's health via enhancing both morphological and biochemical traits that can partially or completely replace the application of chemical insecticides.

Biosynthesis and characterization of extracellular metabolites-based nanoparticles to control the whitefly

The Beauveria spp. were isolated from soil and insect cadavers and confirmed as Beauveria bassiana by molecular identification using a specific primer. The bioefficacy of 14 B. bassiana against whiteflies indicated the highest percent mortality in JAU2, followed by JAU1. The LC₅₀ and LC₉₀ values were found to be 0.043 × 10⁵ and 0.05 × 10¹⁴ conidia.ml^-1, respectively, in JAU2. Extracellular metabolites of B.bassiana are derived and used for the green synthesis of silver nanoparticles (AgNPs). The synthesized green AgNPs were characterized for size (24.8 nm), shape (scanning electron microscopy), stability (200 mV zeta), and purity (energy-dispersive X-ray spectroscopy, 3 keV). A total of 63 extracellular metabolites were identified using LC-MS/QTOF in potent JAU2 with recognition of alcohols, phenols, carboxylic acids, amines, alkynes, and amides as functional groups. The functional groups of green AgNPs were also confirmed in Fourier transforms infrared spectroscopy (FTIR) with the specific spectra in the electromagnetic spectrum. The relationship between identified metabolites of antagonist and the FTIR spectrum of the functional group indicated the involvement of extracellular novel compounds, viz., homoisocitrate, aconitine, phodexin A, capillone, solanocapsine, and anethole in the synthesis of green AgNPs. The efficacy of green AgNPs on whiteflies suggested that corrected percent mortality was observed at 60 µg Ag.ml^-1 at 120 h, which corresponds to the LC₅₀ value (66.42 µg Ag.ml^-1). Results were interpreted to show that green AgNPs synthesized from extracellular metabolites of B.bassiana JAU2 gave better insecticidal activity at LC₅₀ as compared to live antagonist JAU2.

Generation of Stilbene Glycoside with Promising Cell Rejuvenation Activity through Biotransformation by the Entomopathogenic Fungus Beauveria bassiana

A stilbene glycoside (resvebassianol A) (1) with a unique sugar unit, 4-O-methyl-D-glucopyranose, was identified through biotransformation of resveratrol (RSV) by the entomopathogenic fungus Beauveria bassiana to obtain a superior RSV metabolite with enhanced safety. Its structure, including its absolute configurations, was determined using spectroscopic data, HRESIMS, and chemical reactions. Microarray analysis showed that the expression levels of filaggrin, HAS2-AS1, and CERS3 were higher, while those of IL23A, IL1A, and CXCL8 were lower in the resvebassianol A-treated group than in the RSV-treated group, as confirmed by qRT-PCR. Compound 1 exhibited the same regenerative and anti-inflammatory effects as RSV with no cytotoxicity in skin keratinocytes and TNF-α/IFN-γ-stimulated HIEC-6 cells, suggesting that compound 1 is a safe and stable methylglycosylated RSV. Our findings suggest that our biotransformation method can be an efficient biosynthetic platform for producing a broad range of natural glycosides with enhanced safety.

Lasius fuliginosus Nest Carton as a Source of New Promising Bioactive Extracts with Chemopreventive Potential

Six new water extracts (E1-E6) were obtained from nest carton produced by jet black ants Lasius fuliginosus and tested for their biochemical and bioactive properties, including antioxidative and anticancer effects. The present study demonstrated significant qualitative and quantitative differences in the content of individual biochemical constituents, as well as bioactive properties between the investigated samples. All tested extracts demonstrated antioxidant properties (determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) methods), and the highest antioxidative potential was recorded in extracts E1 and E2 (188.96 and 313.67 μg/mL of ascorbic acid equivalent for ABTS and 176.42 and 202.66 μg/mL for DPPH reagent). Furthermore the six extracts exhibited strong inhibitory activity towards human melanoma cells of the A-375 CRL-1619 line in a dose-dependent manner. The most interesting chemopreventive activity was exhibited by extract E2, which inhibited the proliferation of A-375 cells to the greatest extent, while having a minimal effect on Vero cells. The effect on cancer cells has been confirmed using the Electric Cell-substrate Impedance Sensing (ECIS) technique. Significant impedance changes have been detected in A-375 and Vero cells following the administration of extract E2. The obtained results are really promising and constitute the basis for further research on the nest carton of jet black ant.

Pest management via endophytic colonization of tobacco seedlings by the insect fungal pathogen Beauveria bassiana

BACKGROUND

It has been suggested that entomopathogenic fungi can be introduced into plants as endophytes potentially leading to insect control. Here, we sought to identify specific strains of the insect pathogenic fungus, Beauveria bassiana that would form endophytic associations with tobacco (Nicotiana benthamiana) benefitting host plant growth and/or resistance against insect pests and pathogens.

RESULTS

Tobacco seeds were inoculated with six different B. bassiana strains and entophytic colonization, plant growth, and resistance to pathogens and insect pests were evaluated over a 50 day-period. Although all the strains could colonize seedlings, 90% seedling colonization was seen for four strains. Fungal cells could be detected in stems more readily than in leaf and root tissues. Colonization by B. bassiana boosted plant growth with an increased photosynthetic rate, chlorophyll content, and stomatal and trichome density seen in fungal treated plants. Tobacco seedlings colonized by specific B. bassiana strains displayed significantly increased tolerance/resistance against bacterial and fungal pathogens. B. bassiana-colonized seedlings also displayed higher resistance to aphids (Myzus persicae) as compared to untreated controls. Colonization by B. bassiana was shown to trigger both of the salicylic acid (SA) and jasmonate acid (JA) defense pathways, but SA pathway was upregulated much more than JA pathway for some of the tested strains.

CONCLUSION

Specific strains of B. bassiana can be introduced into host plants as endophytes, resulting in promotion of host plant growth, increased resistance to microbial pathogens, and/or increased resistance to insect pests. © 2020 Society of Chemical Industry.

Mitochondrial evolution in the entomopathogenic fungal genus Beauveria

Species in the fungal genus Beauveria are pathogens of invertebrates and have been commonly used as the active agent in biopesticides. After many decades with few species described, recent molecular approaches to classification have led to over 25 species now delimited. Little attention has been given to the mitochondrial genomes of Beauveria but better understanding may led to insights into the nature of species and evolution in this important genus. In this study, we sequenced the mitochondrial genomes of four new strains belonging to Beauveria bassiana, Beauveria caledonica and Beauveria malawiensis, and compared them to existing mitochondrial sequences of related fungi. The mitochondrial genomes of Beauveria ranged widely from 28,806 to 44,135 base pairs, with intron insertions accounting for most size variation and up to 39% (B. malawiensis) of the mitochondrial length due to introns in genes. Gene order of the common mitochondrial genes did not vary among the Beauveria sequences, but variation was observed in the number of transfer ribonucleic acid genes. Although phylogenetic analysis using whole mitochondrial genomes showed, unsurprisingly, that B. bassiana isolates were the most closely related to each other, mitochondrial codon usage suggested that some B. bassiana isolates were more similar to B. malawiensis and B. caledonica than the other B. bassiana isolates analyzed.

Isolation and Bioactivity of Secondary Metabolites from Solid Culture of the Fungus, Alternaria sonchi

The fungus, Alternaria sonchi is considered to be a potential agent for the biocontrol of perennial sowthistle (Sonchus arvensis). A new chlorinated xanthone, methyl 8-hydroxy-3-methyl-4-chloro-9-oxo-9H-xanthene-1-carboxylate (1) and a new benzophenone derivative, 5-chloromoniliphenone (2), were isolated together with eleven structurally related compounds (3-13) from the solid culture of the fungus, which is used for the production of bioherbicidal inoculum of A. sonchi. Their structures were determined by spectroscopic (mostly by NMR and MS) methods. Alternethanoxins A and B, which were reported in A. sonchi earlier, were re-identified as moniliphenone and pinselin, respectively. The isolated compounds were tested for phytotoxic, antimicrobial, insecticidal, cytotoxic and esterase-inhibition activities. They did not demonstrate high phytotoxicity (lesions up to 2.5 mm in diameter/length at a concentration of 2 mg/mL) when tested on leaf disks/segments of perennial sowthistle (Sonchus arvensis) and couch grass (Elytrigia repens). They did not possess acute toxicity to Paramecium caudatum, and showed moderate to low cytotoxicity (IC50 > 25 µg/mL) for U937 and K562 tumor cell lines. However, chloromonilicin and methyl 3,8-dihydroxy-6-methyl-4-chloro-9-oxo-9H-xanthene-1-carboxylate (4) were shown to have antimicrobial properties with MIC 0.5-5 µg/disc. Compound 4 and chloromonilinic acid B were found to have contact insecticidal activity to wheat aphid (Schizaphis graminum) at 1 mg/mL. Compounds 2 and methyl 3,8-dihydroxy-6-methyl-9-oxo-9H-xanthene-1-carboxylate displayed selective carboxylesterase inhibition activity at concentration of 100 µg/mL. Therefore, the waste solid substrate for production of A. sonchi spores can be re-utilized for the isolation of a number of valuable natural products.

Effects of Beauveria bassiana (Hypocreales) on plant growth and secondary metabolites of extracts of hydroponically cultivated chive (Allium schoenoprasum L. [Amaryllidaceae])

The endophytic plant-fungi symbiotic relationship can be explored to improve cultivation of targeted medicinal plant species. The objective of this study was to assess the effects of the cultivation of chive (Allium schoenoprasum) in plant growth medium inoculated with the entomopathogenic fungus, Beauveria bassiana (Hypocreales). Twelve replicates of chive seedlings were exposed to B. bassiana inoculum formulated at concentrations of 0, 1 × 105, 1 × 104 and 1 × 103 conidia mL-1 in a completely randomized design. We assessed plant growth parameters, such as leaf number and plant height weekly and root length, leaf and root fresh and dry weights and secondary metabolites three weeks post-fungal inoculation. The fungus was re-isolated from some of the leaves and roots of the treated plants suggesting that the fungus successfully colonized the plant tissue. Generally, the results indicated that the fungal inoculation had minimal effect on most of the growth parameters assessed in relation to the control. Remarkably, plants exposed to the fungus recorded greater (p < 0.05) total alkaloid, ranging from 2.98 - 3.76 mg atropine equivalent (AE)/g dry weight (DW) compared to the control plants (1.96 mg AE/g DW) for the leaves. This study demonstrated that endophytic fungi could be used to improve the yield of active chemical constituents in cultivated medicinal plants.

A Review on the Synthesis and Bioactivity Aspects of Beauvericin, a Fusarium Mycotoxin

Beauvericin (BEA) is an emerging Fusarium mycotoxin that contaminates food and feeds globally. BEA biosynthesis is rapidly catalyzed by BEA synthetase through a nonribosomal, thiol-templated mechanism. This mycotoxin has cytotoxicity and is capable of increasing oxidative stress to induce cell apoptosis. Recently, large evidence further shows that this mycotoxin has a variety of biological activities and is being considered a potential candidate for medicinal and pesticide research. It is noteworthy that BEA is a potential anticancer agent since it can increase the intracellular Ca²⁺ levels and induce the cancer cell death through oxidative stress and apoptosis. BEA has exhibited effective antibacterial activities against both pathogenic Gram-positive and Gram-negative bacteria. Importantly, BEA exhibits an effective capacity to inhibit the human immunodeficiency virus type-1 integrase. Moreover, BEA can simultaneously target drug resistance and morphogenesis which provides a promising strategy to combat life-threatening fungal infections. Thus, in this review, the synthesis and the biological activities of BEA, as well as, the underlying mechanisms, are fully analyzed. The risk assessment of BEA in food and feed are also discussed. We hope this review will help to further understand the biological activities of BEA and cast some new light on drug discovery.