Myrothecium Verrucaria Research Articles

Chemical Compositions and Anti-Mildew Effects of Cinnamomum micranthum Leaf and Twig Essential Oils on Paper

In this study, we evaluated the anti-mildew effects of paper treated with essential oils of leaves, twigs, and their main constituents from Cinnamomum micranthum. The main ingredients with the greater anti-mildew effects on paper capability were also purified and identified. Fresh leaves and twigs of C. micranthum were hydrodistillated in a Clevenger-type apparatus, and the resulting oil characterized using GC-FID and GC-MS instruments. The leaf essential oil consisted principally of n-decanal (50.1%), ( E)-β-ocimene (7.9%), ( E)-nerolidol (6.5%), and ( E)-β-caryophyllene (3.8%), and the twig oil's main components were τ-cadinol (18.3%), ( E)-β-ocimene (16.4%), α-cadinol (13.6%), n-decanal (10.6%), and β-selinene (5.8%). Comparing the mildew resistance of the oils on paper exhibited that twig oil was the best anti-mildew activity; at 200 μg/cm2, the twig oil completely inhibited the growth of Aspergillus clavatus, Cladosporium cladosporioides, Chaetonium globosum, Myrothecium verrucaria, and Penicillium citrinum. The twig oil was further divided into 8 fractions (TO1-TO8). TO4 fraction had moderate anti-mildew effects; at the concentration of 200 μg/cm2, all fungi strains were totally inhibited, except A niger, and Trichoderma viride, which were 83.5%, and 93.2% inhibited, respectively. The main ingredients of TO4 fraction were τ-cadinol, and α-cadinol, so we isolated and used the for anti-mildew effect tests; τ-cadinol, and α-cadinol showed moderate anti-mildew activities. Since C. micranthum twig essential oil, τ-cadinol, and α-cadinol were exhibited a great anti-mildew effects on paper, they are worth further investigations and utilization.

Molecular characterization of Deciphering Fungal Community structure in Zea mays L. and Triticum Aestivum L

Rhizosphere fungi are strongly associated with plant growth and health by providing nutrients and antagonizing pathogens. Commercially, fungus has multipurpose applications in several sectors including beverages, food items and in medicines. Current study aimed to reveal the core fungal community structure of the two leading cereal crops that are Zea mays L. and Triticum aestivum L. The rhizosphere fungal community was explored via morphology, biochemistry and internal transcribe spacer (ITS) metagenomics. On the basis of morphology, the retrieved fungal strains were imprecisely classified into Ascomycota and Zygomycota. The species including Yeast, Botyritis californica, Rhizopus stolonifer, Alternaria tenuissima, Aspergillus terreus, Aspergillus flavus, Aspergillus nidulans, Aspergillus niger and Microsporum canis were identified on the basis of macroscopy and microscope. Moreover, the biochemical characterization depicted the role of fungi in promotion of plant growth. Majority of the isolates depicted catalase activity, indole production, phosphate solubilization, ammonia production, nitrogenase activity and urease activity. Metagenomics using amplicon sequencing of ITS region revealed the presence of 805 Operational Taxonomic Units (OTUs) with 647 OTUs in Zea mays and 620 OTUs in Triticum aestivum. The fungal phyla found in the rhizosphere of Zea mays L. and Triticum aestivum L. were Ascomycota, Basidiomycota, Zygomycota, Chytridiomycota, Incertae sedis fungi. Ascomycota accounted for 93% and 95% of classified fungi in rhizosphere of Zea mays L. and Triticum aestivum L. respectively. The dominant species found in the rhizosphere soil of Zea mays were Gibberella intricans, Curvularia lunata, Lepidosphaeria nicotiae, Edenia gomezpompae and Myrothecium verrucaria.

Effects of interactions between SPEEK or Nafion ionomers and bilirubin oxidase on O2 enzymatic reduction

Ionomers such as Nafion are used combined to redox enzymes in bioelectrocatalysis in order to prevent enzyme leakage and to enhance proton diffusion. In the search for an alternative to this costly and non-ecofriendly material, sulfonated poly(ether ether ketone) SPEEK, another ionomer free of perfluorinated functions can be envisioned. Here, we investigate the effect of ionomer type and concentration on enzymatic oxygen reduction by the Myrothecium verrucaria bilirubin oxidase (Mv BOD). We show that both SPEEK and Nafion ionomers reduce the catalytic activity of Mv BOD in enzymatic assays in solution as well as in electrochemical experiments once the enzyme is co-adsorbed with the ionomer. A pluridisciplinary approach associating microscopy, UV-Vis spectroscopy, dynamic light scattering, SDS gels and electrochemistry allows to point out a molecular interaction between the polymer particles and the enzyme governed by different principles depending SPEEK or Nafion is considered. The differences in hydrophilicity and conformation of SPEEK compared to Nafion account for a more severe effect on enzyme efficiency.

Engineering bio-interfaces for the direct electron transfer of Myriococcum thermophilum cellobiose dehydrogenase: Towards a mediator-less biosupercapacitor/biofuel cell hybrid

Direct electron transfer (DET) of enzymes on electrode surfaces is highly desirable both for fundamental mechanistic studies and to achieve membrane- and mediator-less bioenergy harvesting. In this report, we describe the preparation and comprehensive structural and electrochemical characterization of a three-dimensional (3D) graphene-based carbon electrode, onto which the two-domain redox enzyme Myriococcum thermophilum cellobiose dehydrogenase (MtCDH) is immobilized. The electrode is prepared by an entirely novel method, which combines in a single step electrochemical reduction of graphene oxide (GO) and simultaneous electrodeposition of positively charged polyethylenimine (PEI), resulting in a well dispersed MtCDH surface. The resulting MtCDH bio-interface was characterized structurally in detail, optimized, and found to exhibit a DET maximum current density of 7.7 ± 0.9 μA cm−2 and a half-lifetime of 48 h for glucose oxidation, attributed to favorable MtCDH surface orientation. A dual, entirely DET-based enzymatic biofuel cell (EBFC) was constructed with a MtCDH bioanode and a Myrothecium verrucaria bilirubin oxidase (MvBOD) biocathode. The EBFC delivers a maximum power density (Pmax) of 7.6 ± 1.3 μW cm−2, an open-circuit voltage (OCV) of 0.60 V, and an operational lifetime over seven days, which exceeds most reported CDH based DET-type EBFCs. A biosupercapacitor/EBFC hybrid was also constructed and found to register maximum power densities 62 and 43 times higher than single glucose/air and lactose/air EBFCs, respectively. This hybrid also shows excellent operational stability with self-charging/discharging over at least 500 cycles.

Genome sequences of Rhizopogon roseolus, Mariannaea elegans, Myrothecium verrucaria, and Sphaerostilbella broomeana and the identification of biosynthetic gene clusters for fungal peptide natural products.

In recent years, a variety of fungal cyclic peptides with interesting bioactivities have been discovered. For many of these peptides, the biosynthetic pathways are unknown and their elucidation often holds surprises. The cyclic and backbone N-methylated omphalotins from Omphalotus olearius were recently shown to constitute a novel class (borosins) of ribosomally synthesized and posttranslationally modified peptides, members of which are produced by many fungi, including species of the genus Rhizopogon. Other recently discovered fungal peptide macrocycles include the mariannamides from Mariannaea elegans and the backbone N-methylated verrucamides and broomeanamides from Myrothecium verrucaria and Sphaerostilbella broomeana, respectively. Here, we present draft genome sequences of four fungal species Rhizopogon roseolus, Mariannaea elegans, Myrothecium verrucaria, and Sphaerostilbella broomeana. We screened these genomes for precursor proteins or gene clusters involved in the mariannamide, verrucamide, and broomeanamide biosynthesis including a general screen for borosin-producing precursor proteins. While our genomic screen for potential ribosomally synthesized and posttranslationally modified peptide precursor proteins of mariannamides, verrucamides, broomeanamides, and borosins remained unsuccessful, antiSMASH predicted nonribosomal peptide synthase gene clusters that may be responsible for the biosynthesis of mariannamides, verrucamides, and broomeanamides. In M. verrucaria, our antiSMASH search led to a putative NRPS gene cluster with a predicted peptide product of 20 amino acids, including multiple nonproteinogenic isovalines. This cluster likely encodes a member of the peptaibols, an antimicrobial class of peptides previously isolated primarily from the Genus Trichoderma. The nonribosomal peptide synthase gene clusters discovered in our screenings are promising candidates for future research.

Effects of N-linked glycans of bilirubin oxidase on direct electron transfer-type bioelectrocatalysis

Bilirubin oxidase from Myrothecium verrucaria (mBOD) is a promising enzyme for catalyzing the four-electron reduction of dioxygen into water and realizes direct electron transfer (DET)-type bioelectrocatalysis. It has two N-linked glycans (N-glycans), and N472 and N482 are known as binding sites. Both binding sites located on opposite side of the type I (T1) Cu, which is the electrode-active site of BOD. We investigated the effect of N-glycans on DET-type bioelectrocatalysis by performing electrochemical measurements using electrodes with controlled surface charges. Two types of BODs with different N-glycans, mBOD and recombinant BOD overexpressed in Pichia pastoris (pBOD), and their deglycosylated forms (dg-mBOD and dg-pBOD) were used in this study. Kinetic analysis of the steady-state catalytic waves revealed that both size and composition of N-glycans affected the orientation of adsorbed BODs on the electrodes. Interestingly, the most favorable orientation was achieved with pBOD, which has the largest N-glycans. Furthermore, the effect of the orientation control by the N-glycans is cooperative with electrostatic interaction.

Creating wealth from waste: An approach for converting organic waste in to value-added products using microbial consortia

In the current scenario, great emphasis is being made on the recovery, recycling, and reconditioning of organic solid waste. With a focus on the bioconversion of organic waste into value-added products, municipal vegetable waste was fractionated into liquid and solid part. The solid fraction was subjected to biodegradation in the presence of different microbial consortia and different enzymes were extracted. The remaining solid stuff was converted into animal feed, followed by the evaluation of its microbiological and chemical indices. Liquid fraction separated from waste was used as a crude medium to grow different bio-fertilizer strains. Among the three consortia, consortium C (Aspergillus terreus and Myrothecium verrucaria) showed the maximum production of amylase, cellulase, xylanase and pectinase after 4 days. Results of the microbiological and chemical parameters of the animal feed prepared from the fermented vegetable waste showed that the various parameters were found to be within the permissible limit. The average concentrations of heavy metals in the compost was found to be within the permissible limit of FCO standard, therefore, it can also be used for agricultural application. For using liquid extract of the vegetable waste, maximum CFU count 1.9 × 106, 1.1 × 106, and 8.7 × 105 was achieved in BAB 1980, BAB 662, and BAB 267 strain, respectively after 30 h of incubation. Thus, the present study demonstrated the bioconversion of vegetable waste into crude enzymes, animal feed, compost, and liquid biofertilizer.

Taxonomic Evaluation of a Bioherbicidal Isolate of Albifimbria verrucaria, Formerly Myrothecium verrucaria

The fungal genus Myrothecium was once polyphyletic but a recent reconsideration of the family Stachybotryaceae spilt it into several genera. The ex-neotype specimen of the species Myrothecium verrucaria is now recognized as Albifimbria verrucaria. The well-studied plant pathogen and candidate bioherbicide CABI-IMI 368023, previously identified as M. verrucaria, was analyzed morphologically and genetically and found to be most consistently aligned with the other representatives of A. verrucaria.

Isolation, characterization and optimizations of laccase producer from soil: A comprehensive study of application of statistical approach to enhance laccase productivity in Myrothecium verrucaria NFCCI 4363

The aim of this work was to find the optimal cultivation conditions of Myrothecium verrucaria NFCCI 4363 to enhance its laccase productivity. Interactive effect of twelve physicochemical parameters were determined and optimized by Plackett-Burman Design (PBD) and Box-Behnken Design (BBD). After statistical experimental performance, significant factors were determined and confirmed as yeast extract, 0.3%; temperature, 25 °C; ABTS, 0.5 mM; MgSO4, 1.5 mM and CuSO4, 0.5 mM. Laccase productivity of M. verrucaria NFCCI 4363 in optimized media was 1415.77 ± 42.34 U/L, more two times increased than unoptimized condition. Stable and optimal conditions of the produced laccase was determined as pH 5, 20 °C and pH 6, 50 °C, respectively. Therefore by statistical approach optimal values of cultural parameters were achieved. Moreover, crude laccase showed more than 70% decolorization potential of bromothymol blue, bromocresol green and bromocresol purple dyes in absence of any of the mediators.

Evaluation of Microbiological Quality of Vermicompost Prepared from Different Types of Organic Wastes using Eisenia fetida

Background: Vermicomposting is the agricultural technique of conversion of organic wastes to a fertile product, which can result in better crop growth and production. However, even though earthworms are the main organisms participating in the process, the microbes associated with it also have an important role to play. These microbes degrade the waste products biochemically and are responsible of the conversion processes. Few studies are carried out on microbial diversity and related enzymes activities in the vermicompost prepared from different organic waste materials. Methods: In this paper, we isolated both bacteria and fungi from seven different types of vermicompost, using different selective media. We also studied the activity of hydrolytic enzymes that are associated with the isolated microbes.Result: It was observed that bacteria like Bacillus sp., Pseudomonas sp., Klebsiella sp., Staphylococcus aureus, Streptococcus, Micrococcus, Actinomycetes, Pigment producing Actinomycetes, Streptomyces, Azotobactor and fungi like Penicillium purpurogenum, Aspergillus sp., Alternaria alternata, Fusarium solani, Rhizopus sp., Mucor hiemalis, Myrothecium verrucaria etc. were present in our vermicompost preparations. The presence of nitrogen fixing bacteria, phosphate solubilizing microorganisms and PGPR indicated the good fertilizer value of the vermicompost samples. It was also observed that the diversity of microbes present supported significant levels of CMCase Exoglucanase, Xylanase, β-Glucosidase, Phosphatase and Urease activities.

Bionematicides as an alternative to methyl bromide fumigation.

Fumigant use in perennial crops can be reduced through prolonging the life of existing orchards. The longer an orchard remains healthy and productive, the less often it will be terminated, fumigated, and replanted. Two trials were conducted to determine the effectiveness of DiTera, a toxin produced by the fungus (Myrothecium verrucaria) and Nema-Q, an extract of the soap bark tree (Quillaja saponaria) for management of root-lesion (Pratylenchus vulnus) and ring (Mesocriconema xenopla) nematodes on walnuts. In the first trial, spring and fall treatments of DiTera were applied each year for four years to variety ‘Chandler’ scion on seedling ‘Paradox’ rootstock, and to own-rooted ‘Chandler’ trees. On ‘Paradox’ rootstock, both DiTera and Nema-Q increased walnut yields (P ≤ 0.05) and produced more vigorous trees (P ≤ 0.05) without significant reductions in nematode populations (P ≤ 0.05). A second trial was conducted with three rates of DiTera and four rates of Nema-Q, combinations of the two products, and an untreated control on ‘Chandler’ scion on ‘Paradox’ rootstock. The highest rate of Nema-Q (P ≤ 0.05), and a combination treatment of DiTera plus Nema-Q (P ≤ 0.05) increased trunk circumference. Several treatments showed reductions in root-lesion and ring nematodes (P ≤ 0.05). Bionematicides can improve yield, growth, and vigor in walnut orchards infested with plant-parasitic nematodes.

Three New Fungal Leaf Spot Diseases of Spinach in the United States and the Evaluation of Fungicide Efficacy for Disease Management.

Leaf spot diseases of spinach, caused by Colletotrichum spinaciae, has become a major production constraint in several production areas, including Texas, in recent years. Leaf spot symptoms were observed in several fields in Texas in 2016 and 2017, with typical anthracnose-like symptoms and leaves with small, circular, and sunken lesions that appeared similar to injury from windblown sand. The lesions were plated on potato dextrose agar, from which fungal cultures were recovered. The fungi were identified based on morphology and sequence analysis of the introns of glutamate synthetase and glyceraldehyde-3-phosphate dehydrogenase (for isolates determined to be Colletotrichum spp.) and the internal transcribed spacer ribosomal DNA (for isolates determined to be Myrothecium spp.). Based on foliar symptoms, fungal colony and spore morphology, pathogenicity tests of fungal isolates on the spinach cultivar 'Viroflay', and DNA sequence analysis of the isolates, the symptoms on spinach leaves for two sets of samples were caused by Colletotrichum coccodes and Colletotrichum truncatum, and leaf spots resembling damage from windblown sand were caused by Myrothecium verrucaria. This is the first report of spinach leaf spot diseases caused by C. coccodes, C. truncatum, and M. verrucaria in the United States. C. coccodes and C. truncatum caused severe symptoms on the spinach cultivar 'Viroflay', whereas M. verrucaria caused symptoms of intermediate severity. Fungicide efficacy tests demonstrated that chlorothalonil, mancozeb, pyraclostrobin, fluxapyroxad + pyraclostrobin, and penthiopyrad were completely effective at preventing leaf spots caused by any of these pathogens when applied 24 h before inoculation of 'Viroflay' plants in greenhouse trials.

Evaluation of Metabolites of Myrothecium verrucaria as Biological Nematicide against Root-knot Nematode, Meloidogyne incognita in Vitro and in Vivo on Sugar Beet Plants

Nematicidal activity of heat-sterilizing filtrate culture of Myrothecium verrucaria was evaluated against Meloidogyne incognita in Vitro and the metabolites formulated as granules of M. verrucaria were prepared and tested on sugar beet plants infested with M. incognita comparison with DiTera™ and Rugby 10%G, under greenhouse conditions. Laboratory results showed that sterilized culture filtrate of the fungus M. verrucaria either by syringe or by autoclaving significantly reduced the percentages of egg hatching and increased the percentage of 2nd stage juveniles (J2) mortality of M. incognita. The most effective reductions of hatching were obtained at 50% concentration with the sterilized filtrate by autoclaving (94.23%), while the most effective reached 96.70% increasing in the percentage of mortality of J2 after 3 days from treating by 50% concentration in case the sterilized filtrate by syringe. Results of greenhouse experiment showed that, all treatments by the prepared fungal formulae of M. verrucaria or DiTerawith different rats significantly reduced the number of galls on sugar beet roots and final nematode population (J2) in soil compared with control (nematode only). The higher rate (0.2 g /pot) was achieved the highest reduction in root-galling (86%) with DiTera treatment and the highest reduction in (J2) with fungal formulae treatment (92.2%). Improvement in plant growth parameters were noticed by treatments. Analysis by GC-MS of the fungus metabolites was identified compounds to have antimicrobial and nematicidal activities. The prepared formulae from the Egyptian isolate of M. verrucaria can be used as safety bio-nematicide against M. incognita on sugar beet.

Chemical Composition, Antioxidant Activity, and Antifungal Effects of Essential Oil from Laurus nobilis L. Flowers Growing in Morocco

In this study, the chemical composition and the antioxidant and antifungal activities of essential oil from Laurus nobilis flowers were examined. The essential oil was prepared using steam distillation in a modified Clevenger-type apparatus. The chemical composition of the obtained essential oil and chemotypes was determined using gas chromatography coupled with mass spectrometry (GC/MS) and gas chromatography with flame ionization detection (GC-FID). Twenty-five volatile compounds were identified, which made up 92.07% of the total essential oil content. The essential oil yield was 1.06% and the most abundant compounds were 1.8-cineole (45.01%), α-caryophyllene (7.54%), germacradienol (6.13%), limonene (4.69%), α-pinene (3.04%), and germacrene D (3.14%). The antifungal activity of the obtained essential oil was tested against seven fungal strains: Aspergillus clavatus, A. niger, Chaetomium globosum, Cladosporium cladosporioides, Myrothecium verrucaria, Penicillium citrinum, and Trichoderma viride. The results indicated that essential oil from L. nobilis flowers exhibited significant antifungal activity against the tested fungal strains with minimum inhibitory concentrations (MICs) ranging from 0.05 to 0.46 mg/mL. The essential oil of L. nobilis also exhibited strong total antioxidant capacity (TAC) as indicated by its ability to scavenge free radical DPPH. Taken together, this study indicates that the essential oil from L. nobilis flowers possesses significant antifungal and antioxidant activities, possibly due to the high level of 1,8-cineole.

Insight into multicopper oxidase laccase from Myrothecium verrucaria ITCC-8447: a case study using in silico and experimental analysis

The oxidation activity of multicopper-oxidases overlaps with different substrates of laccases and bilirubin oxidases, thus in the present study an integrated approach of bioinformatics using homology modeling, docking, and experimental validation was used to confirm the type of multicopper-oxidase in Myrothecium verrucaria ITCC-8447. The result of peptide sequence of M. verrucaria ITCC-8447 enabled to predict the 3 D-structure of multicopper-oxidase. It was overlapped with the structure of laccase and root mean square deviation (RMSD) was 1.53 Å for 533 and, 171 residues. The low binding energy with azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (-5.64) as compared to bilirubin (-4.39) suggested that M. verrucaria ITCC-8447 have laccase-like activity. The experimental analysis confirmed high activity with laccase specific substrates, phenol (18.3 U/L), ampyrone (172.4 U/L) and, ampyrone phenol coupling (50 U/L) as compared to bilirubin oxidase substrate bilirubin (16.6 U/L). In addition, lowest binding energy with ABTS (-5.64), syringaldazine SYZ (-4.83), guaiacol GCL (-4.42), and 2,6-dimethoxyphenol DMP (-4.41) confirmed the presence of laccase. Further, complete remediation of two hazardous model pollutants i.e., phenol and resorcinol (1.5 mM) after 12 h of incubation and low binding energy of −4.32 and, −4.85 respectively confirmed its removal by laccase. The results confirmed the presence of laccase in M. verrucaria ITCC-8447 and its effective bioremediation potential.

Bilirubin oxidase oriented on novel type three-dimensional biocathodes with reduced graphene aggregation for biocathode

Aggregation of reduced graphene oxide (RGO) due to π-π stacking is a recurrent problem in graphene-based electrochemistry, decreasing the effective working area and therefore the performance of the RGO electrodes. Dispersing RGO on three-dimensional (3D) carbon paper electrodes is one strategy towards overcoming this challenge, with partial relief aggregation. In this report, we describe the grafting of negatively charged 4-aminobenzoic acid (4-ABA) onto a graphene functionalized carbon paper electrode surface. 4-ABA functionalization induces separation of the RGO layers, at the same time leading to favorable orientation of the blue multi-copper enzyme Myrothecium verrucaria bilirubin oxidase (MvBOD) for direct electron transfer (DET) in the dioxygen reduction reaction (ORR) at neutral pH. Simultaneous electroreduction of graphene oxide to RGO and covalent attachment of 4-ABA are achieved by applying alternating cathodic and anodic electrochemical potential pulses, leading to a high catalytic current density (Δjcat:193 ± 4 μA cm−2) under static conditions. Electrochemically grafted 4-ABA not only leads to a favorable orientation of BOD as validated by fitting a kinetic model to the electrocatalytic data, but also acts to alleviate RGO aggregation as disclosed by scanning electron microscopy, most likely due to the electrostatic repulsion between 4-ABA-grafted graphene layers. With a half-lifetime of 55 h, the bioelectrode also shows the highest operational stability for DET-type MvBOD-based bioelectrodes reported to date. The bioelectrode was finally shown to work well as a biocathode of a membrane-less glucose/O2 enzymatic biofuel cell with a maximum power density of 22 μW cm−2 and an open circuit voltage of 0.51 V.

Myco-valorization approach using entrapped Myrothecium verrucaria ITCC-8447 on synthetic and natural support via column bioreactor for the detoxification and degradation of anthraquinone dyes

Myco-valorization (Myco-Valtn) concept was explored using Myrothecium verrucaria ITCC-8447 via column bioreactor to remove two anthraquinone (ARq) dyes. Among the three myco-valtn approaches free cell dependent enabled more than 80% removal of Anthraquinone violet R (AVR) and Alizarin cyanine green (ACG) after 48 h at 30 ± 2 °C. Enzymatic treatment removed more than 50% AVR and ACG after 10 min. However, synthetic and natural support entrapment on Scotch-Brite® (SB) and Luffa cylindrica (LC) enabled more than 80% removal in SB-ACG and LC-ACG and more than 60% in SB-AVR and LC-AVR in 6th cycle. The regenerated column enhanced the removal of dye and allowed the column to run for multiple cycles. Further after FTIR XRD and LCMS Q-TOF, analysis it was observed that ACG and AVR were completely degraded and laccase played the key roles in the degradation of ACG and AVR and the degraded metabolites of anthraquinone dyes (ACG and AVR) exhibited much less toxicity than the parent dye using phytotoxicity assays.

Nanosecond Laser-Fabricated Monolayer of Gold Nanoparticles on ITO for Bioelectrocatalysis.

Redox enzymes can be envisioned as biocatalysts in various electrocatalytic-based devices. Among factors that play roles in bioelectrochemistry limitations, the effect of enzyme-enzyme neighboring interaction on electrocatalysis has rarely been investigated, although critical in vivo. We report in this work an in-depth study of gold nanoparticles prepared by laser ablation in the ultimate goal of determining the relationship between activity and enzyme density on electrodes. Nanosecond laser interaction with nanometric gold films deposited on indium tin oxide support was used to generate in situ gold nanoparticles (AuNPs) free from any stabilizers. A comprehensive analysis of AuNP size and coverage, as well as total geometric surface vs. electroactive surface is provided as a function of the thickness of the treated gold layer. Using microscopy and electrochemistry, the long-term stability of AuNP-based electrodes in the atmosphere and in the electrolyte is demonstrated. AuNPs formed by laser treatment are then modified by thiol chemistry and their electrochemical behavior is tested with a redox probe. Finally, enzyme adsorption and bioelectrocatalysis are evaluated in the case of two enzymes, i.e., the Myrothecium verrucaria bilirubin oxidase and the Thermus thermophilus laccase. Behaving differently on charged surfaces, they allow demonstrating the validity of laser treated AuNPs for bioelectrocatalysis.

Effects of Myrothecium verrucaria ZW-2 fermentation filtrates on various plant-parasitic nematodes

This study shows for the first time the effect of the fermentation filtrate of Myrothecium verrucaria, strain ZW-2, on four different species of plant-parasitic nematodes. Our results suggested that the fermentation filtrate of M. verrucaria inhibited hatching of Meloidogyne incognita and Heterodera glycines eggs. The lowest egg hatching rates of H. glycines and M. incognita were 6.3% and 2.0%, respectively, after 15 days of incubation with a fermentation filtrate of M. verrucaria. A 2-week fermentation filtrate had lethal effects on of M. incognita (second stage juveniles), H. glycines and Bursaphelenchus xylophilus. After 72 h of incubation, the following mortality rates were observed: M. incognita J2s, 100%; Hirschmanniella spp., 8.4%; H. glycines J2s, 82.4%; and B. xylophilus, 96.1%. A pot test showed that the mean suppressive rates of H. glycines after one- and two-week fermentation treatments were 78.8% and 91.2%, respectively. There were 0.8 nematodes per tomato root system at seven days after inoculation (DAI) and 4.4 galls and 933.3 eggs per root system at 30 DAI, which were significantly lower than those of the tap water controls (8.0 nematodes, 31.4 galls and 14,622.5 eggs per root system). Our studies confirmed that the fermentation filtrate of strain ZW-2 has nematicidal effects against three plant-parasitic nematodes.

Characterization of Leaf Spot Pathogens from Several Spinach Production Areas in the United States

Leaf spot diseases have become a major concern in spinach production in the United States. Determining the causal agents of leaf spots on spinach, their prevalence and pathogenicity, and fungicide efficacy against these pathogens is vital for effective disease management. Spinach leaves with leaf spots were collected from Texas, California, Arizona, and South Carolina from 2016 to 2018, incubated in a moist chamber, and plated on potato dextrose and tryptic soy agar media. Fungal and bacterial colonies recovered were identified based on morphology and sequence analysis of the internal transcribed spacer rDNA and 16S rRNA, respectively. Two predominant genera were isolated: (i) Colletotrichum spp., which were identified to species based on sequences of both introns of the glutamate synthetase (GS-I) and glyceraldehyde-3-phosphate dehydrogenase (gapdh-I) genes; and (ii) Stemphylium spp., identified to species based on sequences of the gapdh and calmodulin (cmdA) genes. Anthracnose (Colletotrichum spinaciae) and Stemphylium leaf spot (Stemphylium vesicarium and S. beticola) were the predominant diseases. Additional fungi recovered at very limited frequencies that were also pathogenic to spinach included Colletotrichum coccodes, C. truncatum, Cercospora beticola, and Myrothecium verrucaria. All of the bacterial isolates were not pathogenic on spinach. Pathogenicity tests showed that C. spinaciae, S. vesicarium, and S. beticola caused significant leaf damage. The fungicides Bravo WeatherStik (chlorothalonil), Dithane F-45 (mancozeb), Cabrio (pyraclostrobin), and Merivon (fluxapyroxad and pyraclostrobin) were highly effective at reducing leaf spot severity caused by an isolate of each of C. spinaciae and S. vesicarium, when inoculated individually and in combination.