Tolerance and mycoremediation of silver ions by Fusarium solani

Potential fungicidal and antiaflatoxigenic effects of cinnamon essential oils on Aspergillus flavus inhabiting the stored wheat grains

Wheat is one of the essential crops for the human and animal nutrition, however, contamination with aflatoxigenic fungi, due to the improper storage conditions and high humidity, was the main global threats. So, preventing the growth of aflatoxigenic fungi in stored wheat grains, by using different essential oils was the main objective of this work. Aspergillus flavus EFBL-MU12 PP087400, EFBL-MU23 PP087401 and EFBL-MU36 PP087403 isolates were the most potent aflatoxins producers inhabiting wheat grains. The effect of storage conditions of wheat grains "humidity, temperature, incubation period, and pH" on growth of A. flavus, was assessed by the response surface methodology using Plackett-Burman design and FCCD. The highest yield of aflatoxins EFBL-MU12 B1 and B2 by A. flavus grown on wheat grains were 145.3 and 7.6 μg/kg, respectively, at incubation temperature 35°C, 16% moisture contents, initial pH 5.0, and incubated for 14 days. The tested oils had a powerful antifungal activity for the growth and aflatoxins production by A. flavus in a concentration-dependent manner. Among these oils, cinnamon oil had the highest fungicidal activity for A. flavus at 0.125%, with about 85-90 % reduction to the aflatoxins B1 and B2, conidial pigmentation and chitin contents on wheat grains. From the SEM analysis, cinnamon oils had the most deleterious effect on A. flavus with morphological aberrations to the conidial heads, vegetative mycelia, alteration in conidiophores identity, hyphae shrank, and winding. To emphasize the effect of the essential oils on the aflatoxins producing potency of A. flavus, the molecular expression of the aflatoxins biosynthetic genes was estimated by RT-qPCR. The molecular expression of nor-1, afLR, pKsA and afLJ genes was suppressed by 94-96%, due to cinnamon oil at 0.062% compared to the control. Conclusively, from the results, cinnamon oils followed by the peppermint oils displayed the most fungicidal activity for the growth and aflatoxins production by A. flavus grown on wheat grains.

Exploring the infiltrative and degradative ability of Fusarium oxysporum on polyethylene terephthalate (PET) using correlative microscopy and deep learning

Managing the worldwide steady increase in the production of plastic while mitigating the Earth's global pollution is one of the greatest challenges nowadays. Fungi are often involved in biodegradation processes thanks to their ability to penetrate into substrates and release powerful catabolic exoenzymes. However, studying the interaction between fungi and plastic substrates is challenging due to the deep hyphal penetration, which hinders visualisation and evaluation of fungal activity. In this study, a multiscale and multimodal correlative microscopy workflow was employed to investigate the infiltrative and degradative ability of Fusarium oxysporum fungal strain on polyethylene terephthalate (PET) fragments. The use of non-destructive high-resolution 3D X-ray microscopy (XRM) coupled with a state-of-art Deep Learning (DL) reconstruction algorithm allowed optimal visualisation of the distribution of the fungus on the PET fragment. The fungus preferentially developed on the edges and corners of the fragment, where it was able to penetrate into the material through fractures. Additional analyses with scanning electron microscopy (SEM), Raman and energy dispersive X-ray spectroscopy (EDX) allowed the identification of the different phases detected by XRM. The correlative microscopy approach unlocked a more comprehensive understanding of the fungus-plastic interaction, including elemental information and polymeric composition.

Proteomics and metabolomics analyses of camptothecin-producing Aspergillus terreus reveal the integration of PH domain-containing proteins and peptidylprolyl cis/trans isomerase in restoring the camptothecin biosynthesis

IMPORTANCE

Decreasing the camptothecin productivity by fungi with storage and subculturing is the challenge that halts their further implementation to be an industrial platform for camptothecin (CPT) production. The highest differentially abundant proteins were Pleckstrin homology (PH) domain-containing proteins and Peptidyl-prolyl cis/trans isomerase that fluctuated with the subculturing of A. terreus with a remarkable relation to CPT biosynthesis and restored with addition of F. elastica microbiome.

Phytochemical and metabolic profiling of the different Podocarpus species in Egypt: Potential antimicrobial and antiproliferative activities

Podocarpus is the most dominant genus of Podocarpaceae, with higher taxonomical proximity to the Taxaceae, having numerous pharmaceutical applications, however, scarce studies dealing with the physiological and metabolic criteria of Podocarpus in Egypt were reported. Thus, the objective of this work was to assess the physiological and metabolical patterns of the different species of Podocarpus; P. gracilior, P. elongates, P. macrophyllus and P. neriifolius. The highest terpenoids contents were reported in P. neriifolius, followed by P. elongatus, and P. macrophyllus. P. gracilior had the highest antioxidants amount, followed by P. macrophyllus, P. neriifolius and P. elongatus. From the GC/MS metabolic profiling, caryophyllene, β-cadinene, β-cuvebene, vitispirane, β-cadinene and amorphene were the most dominant metabolites in P. gracilior. β-Caryophyllene was the common in P. gracilior, P. elongatus, P. macrophyllus and P. neriifolius with an obvious fluctuation. The plant methanolic extracts have an obvious activity against the multidrug resistant bacteria; E. coli, P. aeruginosa, S. pyogenes and S. aureus, and fungi; A. fumigatus, A. flavus, A. niger and C. albicans in a concentration-dependent manner. The highest Taxol yield was assessed in the extracts of P. elongatus (16.4 μg/gdw), followed by P. macrophyllus, and P. neriifolius. The chemical identity of Taxol derived from P. elongatus was resolved by LC/MS, with molecular mass 854.6 m/z, and similar structural fragmentation pattern of the authentic one. The highest antitumor activity of P. elongatus extracted Taxol was assessed towards HCT-116 (30.2 μg/ml), HepG-2 (53.7 μg/ml) and MCF-7 (71.8 μg/ml). The ITS sequence of P. elongatus "as potent Taxol producer" was deposited on Genbank with accession #ON540734.1, that is the first record of Podocarpus species on Genbank.

Microbial cytosine deaminase is a programmable anticancer prodrug mediating enzyme: antibody, and gene directed enzyme prodrug therapy

Cytosine deaminase (CDA) is a non-mammalian enzyme with powerful activity in mediating the prodrug 5-fluorcytosine (5-FC) into toxic drug 5-fluorouracil (5-FU), as an alternative directed approach for the traditional chemotherapies and radiotherapies of cancer. This enzyme has been frequently reported and characterized from various microorganisms. The therapeutic strategy of 5-FC-CDA involves the administration of CDA followed by the prodrug 5-FC injection to generate cytotoxic 5-FU. The antiproliferative activity of CDA-5-FC elaborates from the higher activity of uracil pathway in tumor cells than normal ones. The main challenge of the therapeutic drug 5-FU are the short half-life, lack of selectivity and emergence of the drug resistance, consistently to the other chemotherapies. So, mediating the 5-FU to the tumor cells by CDA is one of the most feasible approaches to direct the drug to the tumor cells, reducing its toxic effects and improving their pharmacokinetic properties. Nevertheless, the catalytic efficiency, stability, antigenicity and targetability of CDA-5-FC, are the major challenges that limit the clinical application of this approach. Thus, exploring the biochemical properties of CDA from various microorganisms, as well as the approaches for localizing the system of CDA-5-FC to the tumor cells via the antibody directed enzyme prodrug therapy (ADEPT) and gene directed prodrug therapy (GDEPT) were the objectives of this review. Finally, the perspectives for increasing the therapeutic efficacy, and targetability of the CDA-5-FC system were described.

Biotechnological use of the ubiquitous fungus Penicillium sp. 8L2: Biosorption of Ag(I) and synthesis of silver nanoparticles

In this work, the efficiency of the ubiquitous fungus Penicillium sp. 8L2 to remove Ag(I) ions from synthetic solutions and its potential to synthesize silver nanoparticles (AgNPs) was evaluated. Using a Rotatable Central Composite Design pH and biomass concentration were optimized. Maximum biosorption capacity 51.53 mg/g, by Langmuir model, comparing favourably with other reports. The fungal biomass was characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and analyzed before and after the biosorption process by different techniques: X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Ultra-High Resolution Transmission Electron Microscopy and Energy Dispersive X-ray (HR-TEM-EDX) and Ultraviolet-Visible Spectrophotometry (UV-vis). The results showed that the fungus applied several mechanisms to remove Ag(I) ions from the solution and that some of them induced the synthesis of AgNPs. This fact could be verified in the synthesis tests from the cell extract in which aqueous suspensions with high concentrations of AgNPs were obtained. These nanoparticles had diameters between 2 and 9 nm and therefore a high potential for their use as biocidal agents. The results indicated that the synthesis of nanoparticles could be an added value to the heavy metal biosorption process.

Microbial silver resistance mechanisms: recent developments

In this mini-review, after a brief introduction into the widespread antimicrobial use of silver ions and nanoparticles against bacteria, fungi and viruses, the toxicity of silver compounds and the molecular mechanisms of microbial silver resistance are discussed, including recent studies on bacteria and fungi. The similarities and differences between silver ions and silver nanoparticles as antimicrobial agents are also mentioned. Regarding bacterial ionic silver resistance, the roles of the sil operon, silver cation efflux proteins, and copper-silver efflux systems are explained. The importance of bacterially produced exopolysaccharides as a physiological (biofilm) defense mechanism against silver nanoparticles is also emphasized. Regarding fungal silver resistance, the roles of metallothioneins, copper-transporting P-type ATPases and cell wall are discussed. Recent evolutionary engineering (adaptive laboratory evolution) studies are also discussed which revealed that silver resistance can evolve rapidly in bacteria and fungi. The cross-resistance observed between silver resistance and resistance to other heavy metals and antibiotics in bacteria and fungi is also explained as a clinically and environmentally important issue. The use of silver against bacterial and fungal biofilm formation is also discussed. Finally, the antiviral effects of silver and the use of silver nanoparticles against SARS-CoV-2 and other viruses are mentioned. To conclude, silver compounds are becoming increasingly important as antimicrobial agents, and their widespread use necessitates detailed understanding of microbial silver response and resistance mechanisms, as well as the ecological effects of silver compounds. Figure created with BioRender.com.

Physiological Response of Saccharomyces cerevisiae to Silver Stress

Silver nanoparticle (AgNP) production and their use as antimicrobial agents is a current area of active research. Biosynthesis is the most sustainable production method, and fungi have become candidates of interest in AgNP production. However, investigations into the physiological responses of fungi due to silver exposure are scanty. This present work utilized two strains of Saccharomyces cerevisiae (one used in commercial fermentation and a naturally occurring strain) to determine the physiological consequences of their transient exposure to AgNO₃. The assessments were based on studies involving growth curves, minimal inhibitory concentration assays, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) imaging, and inductively coupled plasma optical emission spectroscopy (ICP-OES). Results indicated (a) the capability of S. cerevisiae to produce silver nanoparticles, even at elevated levels of exposure; (b) strain origin had no significant impact on S. cerevisiae physiological response to AgNO₃; and (c) coexposure to copper and silver significantly increased intracellular copper, silver, and calcium in treated yeast cells. In addition, electron microscopy and ICP-OES results revealed that both strains internalized silver after exposure, resulting in the shrunken and distorted physical appearance visible on SEM micrographs of treated cells. Though a promising candidate for AgNPs biosynthesis, this study analyzed the effects of transient silver exposure on S. cerevisiae growth physiology and morphology.

Fungal and oomycete pathogens and heavy metals: an inglorious couple in the environment

Heavy metal (HM) contamination of the environment is a major problem worldwide. The rate of global deposition of HMs in soil has dramatically increased over the past two centuries and there of facilitated their rapid accumulation also in living systems. Although the effects of HMs on plants, animals and humans have been extensively studied, yet little is known about their effects on the (patho)biology of the microorganisms belonging to a unique group of filamentous eukaryotic pathogens, i.e., fungi and oomycetes. Much of the literature concerning mainly model species has revealed that HM stress affects their hyphal growth, morphology, and sporulation. Toxicity at cellular level leads to disturbance of redox homeostasis manifested by the formation of nitro-oxidative intermediates and to the induction of antioxidant machinery. Despite such adverse effects, published data is indicative of the fact that fungal and oomycete pathogens have a relatively high tolerance to HMs in comparison to other groups of microbes such as bacteria. Likely, these pathogens may harbor a network of detoxification mechanisms that ensure their survival in a highly HM-polluted (micro)habitat. Such a network may include extracellular HMs immobilization, biosorption to cell wall, and/or their intracellular sequestration to proteins or other ligands. HMs may also induce a hormesis-like phenomenon allowing the pathogens to maintain or even increase fitness against chemical challenges. Different scenarios linking HMs stress and modification of the microorganisms pathogenicity are disscused in this review.

Iron stress response and bioaccumulation potential of three fungal strains isolated from sewage-irrigated soil

AIMS

Contamination with heavy metal (HM) is a severe environmental issue. Therefore, there is a pressing need to create environmentally safe and cost-effective HM bioremediation approaches.

METHODS AND RESULTS

Three iron-tolerant fungal strains were isolated from sewage-irrigated soils, molecularly identified and deposited in the GenBank as Aspergillus flavus MT639638, A. terreus MT605370 and Fusarium oxysporum MT605399. The fungal growth, minimum inhibitory concentration (MIC), tolerance index (TI), removal efficiency, bioaccumulation, and enzymatic and non-enzymatic antioxidants were determined. Based on MIC values, A. flavus MT639638 was the most resistant strain. F. oxysporum displayed the highest percent removal efficiency (93.65% at 4000 mg L^-1 ) followed by A. flavus (92.92%, at 11,000 mg L^-1 ), and A. terreus (91.18% at 3000 mg L^-1 ). F. oxysporum was selected based on its highly sensitivity for further characterization of its response to Fe(II) stress using TEM, SEM and EDX, in addition to HPLC analysis of organic acids. These analyses demonstrated the localization of bioaccumulated Fe(II) and ultrastructural changes induced by iron and indicated induction release of organic acids.

CONCLUSIONS

Our fungal strains showed an effective capacity for removal of Fe(II) via bioaccumulation and biosorption mechanisms which were supported by instrumental analyses. The iron tolerance potentiality was mediated by induction of selected antioxidative enzymes and biomolecules.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study depicts a potential utilization of the three fungal strains for the bioremediation of iron-contaminated soils.

Biosorption mechanisms of Ag(I) and the synthesis of nanoparticles by the biomass from Botryosphaeria rhodina MAMB-05

Two biomass types of Botryosphaeria rhodina MAMB-05 (VMSM and M3) were evaluated to determine their effectiveness in removing Ag(I) ions from synthetic solutions. Both biomass types obtained good results in the biosorption process with maximum biosorption capacities (q_m) for the Langmuir model of 34.67 and 39.23 mg Ag(I)/g dry biomass for M3 and VMSM, respectively. The biomass was characterized by X-ray microfluorescence and Fourier-transform-infrared spectroscopy (FT-IR). After the biosorption process, the mechanisms involved in biosorption were studied by FT-IR, X-ray diffraction (XRD), Field Emission Scanning Microscopy/Energy Dispersive X-ray Analysis (FESEM/EDX) and Ultraviolet-Visible Spectrophotometry. The results demonstrated the participation of various mechanisms in the retention of silver on biomass (bioadsorption, complexation, ion exchange, covalent bonding) that resulted in the formation of silver chloride nanoparticles (AgCl-NPs) and silver nanoparticles (AgNPs). The sizes of AgCl-NPs (chlorargyrite) according to the Debye-Scherrer equation were 19.29 nm (VMSM biomass) and 24.9 nm for the M3 type. For AgNPs the crystal size was between 1.5 and 0.8 nm for VMSM and M3 respectively. Furthermore, it was found that an undetermined fraction of the silver nanoparticles after biosorption remained in solution, which could be advantageous for their recovery.

Biosynthesis and Anti-Mycotoxigenic Activity of Zingiber officinale Roscoe-Derived Metal Nanoparticles

Mycotoxigenic fungi have attracted special attention due to their threat to food security and toxicity to human health. Aqueous extract of Zingiber officinale Roscoe was used as reducing and capping agent for the synthesis of silver (AgNPs), copper (CuNPs), and zinc oxide (ZnONPs) nanoparticles. UV-Visible spectra of the AgNPs, CuNPs, and ZnONPs showed absorption peaks at λmax 416 nm, 472 nm, and 372 nm, respectively. Zeta potential of AgNPs, CuNPs, and ZnONPs were -30.9, -30.4 and -18.4 mV, respectively. ZnONPs showed the highest activity against Aspergillus awamori ZUJQ 965830.1 (ZOI 20.9 mm and MIC 24.7 µg/mL). TEM micrographs of ZnONPs-treated A. awamori showed cracks and pits in the cell wall, liquefaction of the cytoplasmic content, making it less electron-dense. The sporulation and ochratoxin A production of A. awamori was inhibited by ZnONPs in a concentration-dependent pattern. The inhibition percentage of OTA were 45.6, 84.78 and 95.65% for 10, 15, 20 of ZnONPs/mL, respectively.

Toxicity treatment of tobacco wastes using experimental design by filamentous fungi

Cigarette product waste contains toxic chemicals, including human carcinogens, which leach into and accumulate in the environment and represent a current environmental problem neglected for too long. This study aimed to select filamentous fungi capable of decreasing tobacco extract toxicity as an alternative to a future bioremediation process. The 38 isolates obtained from Culture collection of microorganisms to biotechnological and environmental importance – CCMIBA (Brazil) were cultivated in yeast extract (10 g.L⁻¹) and dextrose (10 g.L⁻¹) containing cigarette tobacco extract (200 mL.L⁻¹) for seven days at 28 °C on a rotary shaker at 150 rpm. The fungal growth rate was determined to infer fungal tolerance to tobacco extract, and supernatants from cultivated fungi were used to run the toxicity test using Allium cepa assay. The Fusarium sp. strain I.17, isolated from cigarette waste, was the only lineage capable of growing in 20% (v/v) of cigarette tobacco extract, allowed the onions to root, and was selected for optimization. Initially, for the experimental design to selected fungus, a fractional factorial experimental design 2⁵⁻¹ was used to examine the effects of yeast extract, cigarette tobacco extract concentration, dextrose, copper sulfate and pH fungal cultivation. The supernatants of these assays were used to run the toxicity test, and yeast extract and copper sulfate were statistically significant in the fungal growth for the decreasing toxicity process and this variable as were select to central composite design. The highest concentration of yeast extract negatively influenced the toxicity decrease, 0.5% of yeast extract in the culture media is the maximum concentration to achieve the best result and to copper sulfate the best result was using 10 μmol.L⁻¹. In conclusion, the experimental design optimized more than seven times the efficiency of tobacco toxicity reducing, resulting in more than 50% of onion root growth, demonstrating the methodology success. And ITS region was used to taxonomy and molecular phylogeny of the isolate Fusarium sp. strain I.17. These results suggest that Fusarium sp. strain I.17 can be used as a potential microorganism to toxicity treatment of cigarette wastes, minimizing the environmental impact of direct burning.

Bioremediation and tolerance of zinc ions using Fusarium solani

Evaluating the mechanism of tolerance and biotransformation Zn(II) ions by Fusarium solani based on the different physiological was the objective of this work. The physical properties of synthesized ZnONPs was determined by UV-spectroscopy, transmission electron microscope, and X-ray powder diffraction. The structural and anatomical changes of F. solani in response to Zn(II) was examined by TEM and SEM. From the HPLC profile, oxalic acid by F. solani was strongly increased by about 10.5 folds in response to 200 mg/l Zn(II) comparing to control cultures. The highest biosorption potential were reported at pH 4.0 (alkali-treated biomass) and 5.0 (native biomass), at 600 mg/l Zn(II) concentration, incubation temperature 30 °C, and contact time 40 min (alkali-treated biomass) and 6 h (native biomass). From the FT-IR spectroscopy, the main functional groups implemented on this remediation were C-S stretching, C=O C=N, C-H bending, C-N stretching and N-H bending. From the EDX spectra, fungal cellular sulfur and phosphorus compounds were the mainly compartments involved on ZN(II) binding.

Mycosynthesis of ZnO Nanoparticles Using Trichoderma spp. Isolated from Rhizosphere Soils and Its Synergistic Antibacterial Effect against Xanthomonas oryzae pv. oryzae

The Plant Growth Promoting Fungi (PGPF) is used as a source of biofertilizers due to their production of secondary metabolites and beneficial effects on plants. The present work is focused on the co-cultivation of Trichoderma spp. (T. harzianum (PGT4), T. reesei (PGT5) and T. reesei (PGT13)) and the production of secondary metabolites from mono and co-culture and mycosynthesis of zinc oxide nanoparticles (ZnO NPs), which were characterized by a UV visible spectrophotometer, Powder X-ray Diffraction (PXRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDAX) and Transmission Electron Microscope (TEM) and Selected Area (Electron) Diffraction (SAED) patterns. The fungal secondary metabolite crude was extracted from the mono and co-culture of Trichoderma spp. And were analyzed by GC-MS, which was further subjected for antibacterial activity against Xanthomonas oryzae pv. Oryzae, the causative organism for Bacterial Leaf Blight (BLB) in rice. Our results showed that the maximum zone of inhibition was recorded from the co-culture of Trichoderma spp. rather than mono cultures, which indicates that co-cultivation of beneficial fungi can stimulate the synthesis of novel secondary metabolites better than in monocultures. ZnO NPs were synthesized from fungal secondary metabolites of mono cultures of Trichoderma harzianum (PGT4), Trichoderma reesei (PGT5), Trichoderma reesei (PGT13) and co-culture (PGT4 + PGT5 + PGT13). These ZnO NPs were checked for antibacterial activity against Xoo, which was found to be of a dose-dependent manner. In summary, the biosynthesized ZnO NPs and secondary metabolites from co-culture of Trichoderma spp. are ecofriendly and can be used as an alternative for chemical fertilizers in agriculture.