Vibrio gazogenes inhibits aflatoxin production through downregulation of aflatoxin biosynthetic genes in Aspergillus flavus

Aspergillus flavus is an opportunistic pathogen of oilseed crops such as maize, peanut, cottonseed, and tree nuts and produces carcinogenic secondary metabolites known as aflatoxins during seed colonization. Aflatoxin contamination not only reduces the value of the produce but also is a health hazard to humans and animals. Previously, we observed inhibition of A. flavus aflatoxin biosynthesis upon exposure to the marine bacterium, Vibrio gazogenes (Vg). In this study, we used RNA sequencing to examine the transcriptional profiles of A. flavus treated with both live and heat-inactivated dead Vg and control samples. Fungal biomass, total accumulated aflatoxins, and expression profiles of genes constituting secondary metabolite biosynthetic gene clusters were determined at 24, 30, and 40 h after treatment. Statistically significant reductions in total aflatoxins were detected in Vg-treated samples as compared to control samples at 40 h. But no statistical difference in fungal biomass was observed upon these treatments. The Vg treatments were most effective on aflatoxin biosynthesis as was reflected in significant downregulation of majority of the genes in the aflatoxin gene cluster including the aflatoxin pathway regulator gene, aflR. Along with aflatoxin genes, we also observed significant downregulation in some other secondary metabolite gene clusters including cyclopiazonic acid and aflavarin, suggesting that the treatment may inhibit other secondary metabolites as well. Finally, a weighted gene correlation network analysis identified an upregulation of ten genes that were most strongly associated with Vg-dependent aflatoxin inhibition and provide a novel start-point in understanding the mechanisms that result in this phenomenon.

It Works! Organic-Waste-Assisted Trichoderma spp. Solid-State Fermentation on Agricultural Digestate

This study aimed at valorizing digestate through Trichoderma spp. solid-state fermentation (SSF) to produce a potentially ameliorated fertilizer combined with fungal biomass as a value-added bioproduct. Plant-growth-promoting Trichoderma atroviride Ta13, T. reesei RUT-C30, T. asperellum R, and T. harzianum T-22 were tested on different SSF substrates: whole digestate (WD), digestate dried up with wood sawdust (SSF1), and digestate enriched with food waste and dried up with wood sawdust (SSF2). The fungal biomass was quantified by using a qPCR assay. The growth of the four Trichoderma spp. was only observed on the SSF2 substrate. The highest quantity of mycelium was produced by T. reesei RUT-30 (689.80 ± 80.53 mg/g substrate), followed by T. atroviride Ta13, and T. asperellum R (584.24 ± 13.36 and 444.79 ± 91.02 mg/g substrate). The germination of Lepidium sativum seeds was evaluated in order to assess the phytoxicity of the Trichoderma-enriched substrate. The treatments with 7.5% SSF2-R, 3.75% SSF2-T-22, and 1.8% SSF2-Ta13 equally enhanced the root elongation in comparison to the non-fermented SSF-2. This study demonstrated that digestate, mixed with agro-food waste, was able to support the cultivation of Trichoderma spp., paving the way to the valorization of fermented digestate as a proper biofertilizer.

Growth and Fatty Acid Profile of the Aspergillus terreus in Different Culture Media and Temperatures

Fungi are a promising alternative source of oil to produce biodiesel, still very little known. The identification of a species with desirable characteristics is a fundamental component to achieve the economic viability of the process. The study aimed to carry out the evaluation of the fungus Aspergillus terreus in different culture media and different temperatures, the production of fungal biomass and in line with obtaining the profile of methyl esters of fatty acids. The fungal biomass revealed that in the NBRIP medium at both a temperature of 29 ºC and 36 ºC, it resulted in a great potential in the production of saturated fatty acids (SFA), which have excellent combustion properties, reaching values of 35.89 and 34,89%, respectively. For most species, the fuel would need to be mixed to make up culture conditions to be optimized and achieve the correct lipid profile, so that the fungal fuel meets European biodiesel production standards (EN 14214). Aspergillus terreus from iron ore tailings proved to be a promising microbial biomass as an energy source in the production of biodiesel.

Biochemical Profile by GC–MS of Fungal Biomass Produced from the Ascospores of Tirmania nivea as a Natural Renewable Resource

The edible fruiting bodies of desert truffles are seasonally collected and consumed in many regions of the world. Although they are very expensive, they are bought and sold as a result of considerable scientific reports confirming their health and nutritional benefits. This study aimed to conduct laboratory production of the fungal biomass of Tirmania nivea as a natural renewable resource of many active biological compounds using an artificial growth medium. The T. nivea collected from Hafar Al-Batin, which is north of Saudi Arabia, and their ascospores were harvested and used to produce fungal biomass in potato dextrose broth. The cultivation was conducted using a shaking incubator at 25 °C for two weeks at 200 rpm. The crud extracts of the fungal biomass and mycelium-free broth were prepared using ethyl acetate, methanol and hexane. Preliminary gas chromatography–mass spectrometry (GC–MS) analysis and their biological activity as antimicrobial agents were investigated. The results showed that the crude extracts have biological activity against mold, yeast and bacteria. The preliminary GC–MS analysis reported that the fungal biomass and extracellular metabolites in the growth medium are industrial renewable resources of several biological compounds that could be used as antifungal, antibacterial, antiviral, anticancer, antioxidant, anti-trypanosomal and anti-inflammatory agents.

Bacterial and fungal communities experience rapid succession during the first year following a wildfire in a California chaparral.

The rise in wildfire frequency in the western United States has increased interest in secondary succession. However, despite the role of soil microbial communities in plant regeneration and establishment, microbial secondary succession is poorly understood owing to a lack of measurements immediately post-fire and at high temporal resolution. To fill this knowledge gap, we collected soils at 2 and 3 weeks and 1, 2, 3, 4, 6, 9, and 12 months after a chaparral wildfire in Southern California. We assessed bacterial and fungal biomass with qPCR of 16S and 18S and richness and composition with Illumina MiSeq sequencing of the 16S and ITS2 amplicons. We found that fire severely reduced bacterial biomass by 47% and richness by 46%, but the impacts were stronger for fungi, with biomass decreasing by 86% and richness by 68%. These declines persisted for the entire post-fire year, but bacterial biomass and richness oscillated in response to precipitation, whereas fungal biomass and richness did not. Fungi and bacteria experienced rapid succession, with 5-6 compositional turnover periods. As with plants, fast-growing surviving microbes drove successional dynamics. For bacteria, succession was driven by the phyla Firmicutes and Proteobacteria, with the Proteobacteria Massilia dominating all successional time points, and the Firmicutes (Domibacillus and Paenibacillus) dominating early- to mid-successional stages (1-4.5 months), while the Proteobacteria Noviherbaspirillum dominated late successional stages (4.5-1 year). For fungi, succession was driven by the phyla Ascomycota, but ectomycorrhizal basidiomycetes, and the heat-resistant yeast, Geminibasidium were present in the early successional stages (1 month). However, pyrophilous filamentous Ascomycetes Pyronema, Penicillium, and Aspergillus, dominated all post-fire time points. While wildfires vastly decrease bacterial and fungal biomass and richness, similar to plants, pyrophilous bacteria and fungi increase in abundance and experience rapid succession and compositional turnover in the first post-fire year, with potential implications for post-fire chaparral regeneration

Comparison of non-subjective relative fungal biomass measurements to quantify the Leptosphaeria maculans—Brassica napus interaction

Background Blackleg disease, caused by the fungal pathogen Leptosphaeria maculans, is a serious threat to canola (Brassica napus) production worldwide. Quantitative resistance to this disease is a highly desirable trait but is difficult to precisely phenotype. Visual scores can be subjective and are prone to assessor bias. Methods to assess variation in quantitative resistance more accurately were developed based on quantifying in planta fungal biomass, including the Wheat Germ Agglutinin Chitin Assay (WAC), qPCR and ddPCR assays. Results Disease assays were conducted by inoculating a range of canola cultivars with L. maculans isolates in glasshouse experiments and assessing fungal biomass in cotyledons, petioles and stem tissue harvested at different timepoints post-inoculation. PCR and WAC assay results were well correlated, repeatable across experiments and host tissues, and able to differentiate fungal biomass in different host-isolate treatments. In addition, the ddPCR assay was shown to differentiate between L. maculans isolates. Conclusions The ddPCR assay is more sensitive in detecting pathogens and more adaptable to high-throughput methods by using robotic systems than the WAC assay. Overall, these methods proved accurate and non-subjective, providing alternatives to visual assessments to quantify the L. maculans-B. napus interaction in all plant tissues throughout the progression of the disease in seedlings and mature plants and have potential for fine-scale blackleg resistance phenotyping in canola.

Influence of sucrosis on the degradation of pesticide by white rot fungus

The influence of sucrose on the removal of Paraquat (PQT) in synthetic aqueous medium was evaluated by Phanerochaete chrysosporium. Initially, a toxicity test was performed on plates containing paraquat at concentrations of 1, 5, 10, 20 and 30 mg.L-1. Then, they were carried out in batches - agitated batch (RBA) and sequential batch (RBS). Four reactors were submitted, containing medium with 30 mg.L-1 of paraquat, under a reaction time of 144 h, the reactors being RBA-2 and RBS-2 with the addition of 2 gL-1 of sucrose, and without the adding sucrose to the RBA-0 and RBS-0 reactors. In all reactors, paraquat was removed, but in RBS-0, the best mean removal efficiency was obtained (41.1 ± 0.89%). The best values ​​of apparent speed of degradation (k) were found in reactors with sucrose RBA-2 and RBS-2, 0.015 ± 0.002 h-1 and 0.018 ± 0.002 h-1, respectively, indicating that the addition of sucrose influenced the speed removal of paraquat. It was also verified that the pollutant was not completely removed by adsorption to fungal biomass, which microorganisms predominated in the medium at the end of the treatment, demonstrating their role in the paraquat bioremediation process. Therefore, the addition of sucrose influenced the removal speed of the PQT and COD, but not the removal efficiency.

Innovative method for encapsulating highly pigmented biomass from Aspergillus nidulans mutant for copper ions removal and recovery

Biosorption has been considered a promising technology for the treatment of industrial effluents containing heavy metals. However, the development of a cost-effective technique for biomass immobilization is essential for successful application of biosorption in industrial processes. In this study, a new method of reversible encapsulation of the highly pigmented biomass from Aspergillus nidulans mutant using semipermeable cellulose membrane was developed and the efficiency of the encapsulated biosorbent in the removal and recovery of copper ions was evaluated. Data analysis showed that the pseudo-second-order model better described copper adsorption by encapsulated biosorbent and a good correlation (r2 > 0.96) to the Langmuir isotherm was obtained. The maximum biosorption capacities for the encapsulated biosorbents were higher (333.5 and 116.1 mg g-1 for EB10 and EB30, respectively) than that for free biomass (92.0 mg g-1). SEM-EDXS and FT-IR analysis revealed that several functional groups on fungal biomass were involved in copper adsorption through ion-exchange mechanism. Sorption/desorption experiments showed that the metal recovery efficiency by encapsulated biosorbent remained constant at approximately 70% during five biosorption/desorption cycles. Therefore, this study demonstrated that the new encapsulation method of the fungal biomass using a semipermeable cellulose membrane is efficient for heavy metal ion removal and recovery from aqueous solutions in multiple adsorption-desorption cycles. In addition, this reversible encapsulation method has great potential for application in the treatment of heavy metal contaminated industrial effluents due to its low cost, the possibility of recovering adsorbed ions and the reuse of biosorbent in consecutive biosorption/desorption cycles with high efficiency of metal removal and recovery.