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Heavy metals (HMs) contamination is a major issue produced by industrial and mining processes, among other human activities. The capacity of fungi to eliminate HMs from the environment has drawn attention. However, the main process by which fungi protect the environment against the damaging effects of these HMs, such as cadmium (Cd), is still unknown. In this study, some fungi were isolated from HMs-polluted soil. The minimum inhibitory concentrations (MICs) and the tolerance indices of the tested isolates against Cd were evaluated. Moreover, molecular identification of the most tolerant fungal isolates ( Aspergillus niger and A. terreus ) was done and deposited in the GenBank NCBI database. The results showed that the colony diameter of A. niger and A. terreus was decreased gradually by the increase of Cd concentration. Also, all the tested parameters were influenced by Cd concentration. Lipid peroxidation (MDA content) was progressively increased by 12.95–105.95% ( A. niger ) and 17.27–85.38% ( A. terreus ), respectively, from 50 to 200 mg/L. PPO, APX, and POD enzymes were elevated in the presence of Cd, thus illustrating the appearance of an oxidative stress action. Compared to the non-stressed A. niger , the POD and PPO activities were enhanced by 92.00 and 104.24% at 200 mg/L Cd. Also, APX activity was increased by 58.12% at 200 mg/L. Removal efficiency and microbial accumulation capacities of A. niger and A. terreus have also been assessed. Production of succinic and malic acids by A. niger and A. terreus was increased in response to 200 mg/L Cd, in contrast to their controls (Cd-free), as revealed by HPLC analysis. These findings helped us to suggest A. niger and A. terreus as the potential mycoremediation microbes that alleviate Cd contamination. We can learn more about these fungal isolates’ resistance mechanisms against different HMs through further studies.

Bacterial-fungal interactions influence microbial community performance of most ecosystems and elicit specific microbial behaviours, including stimulating specialised metabolite production. Here, we use a co-culture experimental evolution approach to investigate bacterial adaptation to the presence of a fungus, using a simple model of bacterial-fungal interactions encompassing the bacterium Bacillus subtilis and the fungus Aspergillus niger . We find in one evolving population that B. subtilis was selected for enhanced production of the lipopeptide surfactin and accelerated surface spreading ability, leading to inhibition of fungal expansion and acidification of the environment. These phenotypes were explained by specific mutations in the DegS-DegU two-component system. In the presence of surfactin, fungal hyphae exhibited bulging cells with delocalised secretory vesicles possibly provoking an RlmA-dependent cell wall stress. Thus, our results indicate that the presence of the fungus selects for increased surfactin production, which inhibits fungal growth and facilitates the competitive success of the bacterium. Bacterial-fungal interactions can stimulate the production of specialised microbial metabolites. Here, Richter et al. use co-culture experimental evolution to show that the presence of a fungus selects for increased surfactin production in the bacterium Bacillus subtilis , which inhibits fungal growth and facilitates the competitive success of the bacterium.

Among opportunistically pathogenic filamentous fungi of the Aspergillus genus, Aspergillus fumigatus stands out as a drastically more prevalent cause of infection than others. Utilizing the zebrafish embryo model, we applied a combination of non-invasive real-time imaging and genetic approaches to compare the infectious development of A . fumigatus with that of the less pathogenic A . niger . We found that both species evoke similar immune cell migratory responses, but A . fumigatus is more efficiently phagocytized than A . niger . Though efficiently phagocytized, A . fumigatus conidia retains the ability to germinate and form hyphae from inside macrophages leading to serious infection even at relatively low infectious burdens. By contrast, A . niger appears to rely on extracellular germination, and rapid hyphal growth to establish infection. Despite these differences in the mechanism of infection between the species, galactofuranose mutant strains of both A . fumigatus and A . niger display attenuated pathogenesis. However, deficiency in this cell wall component has a stronger impact on A . niger , which is dependent on rapid extracellular hyphal growth. In conclusion, we uncover differences in the interaction of the two fungal species with innate immune cells, noticeable from very early stages of infection, which drive a divergence in their route to establishing infections.

The cell wall integrity pathway is activated in response to cell wall stress (CWS). The defense system in aspergilli employs three transcription factors—RlmA, MsnA, and CrzA—which also facilitate adaptation to various abiotic stressors and involve alterations in cytosolic osmolyte composition and membrane lipid profiles. However, their role in adaptation to CWS remains unclear. In Aspergillus niger, CWS induced by Congo red and calcofluor white caused a pronounced cessation of apical growth, accompanied by hyphal globular swelling and an increase in chitin and glucan content in the cell wall. Regarding the osmolyte composition, which predominantly consists of low levels of glycerol and mannitol, glycerol levels were reduced under CWS. Neither the composition nor the amounts of membrane and storage lipids changed following CWS; however, the degree of unsaturation of phospholipids increased due to a higher proportion of linolenic acid, potentially enhancing membrane fluidity. These minor rearrangements of membrane lipids and osmolytes do not confirm their involvement in the adaptation to CWS induced by Congo red and calcofluor white, contrary to previous assumptions based on studies of cell wall integrity pathways.

Background Second generation (2G) ethanol is produced by breaking down lignocellulosic biomass into fermentable sugars. In Brazil, sugarcane bagasse has been proposed as the lignocellulosic residue for this biofuel production. The enzymatic cocktails for the degradation of biomass-derived polysaccharides are mostly produced by fungi, such as Aspergillus niger and Trichoderma reesei . However, it is not yet fully understood how these microorganisms degrade plant biomass. In order to identify transcriptomic changes during steam-exploded bagasse (SEB) breakdown, we conducted a RNA-seq comparative transcriptome profiling of both fungi growing on SEB as carbon source. Results Particular attention was focused on CAZymes, sugar transporters, transcription factors (TFs) and other proteins related to lignocellulose degradation. Although genes coding for the main enzymes involved in biomass deconstruction were expressed by both fungal strains since the beginning of the growth in SEB, significant differences were found in their expression profiles. The expression of these enzymes is mainly regulated at the transcription level, and A. niger and T. reesei also showed differences in TFs content and in their expression. Several sugar transporters that were induced in both fungal strains could be new players on biomass degradation besides their role in sugar uptake. Interestingly, our findings revealed that in both strains several genes that code for proteins of unknown function and pro-oxidant, antioxidant, and detoxification enzymes were induced during growth in SEB as carbon source, but their specific roles on lignocellulose degradation remain to be elucidated. Conclusions This is the first report of a time-course experiment monitoring the degradation of pretreated bagasse by two important fungi using the RNA-seq technology. It was possible to identify a set of genes that might be applied in several biotechnology fields. The data suggest that these two microorganisms employ different strategies for biomass breakdown. This knowledge can be exploited for the rational design of enzymatic cocktails and 2G ethanol production improvement.

In this study, acorn starch was investigated as a new material for fermenting production of citric acid by using a tannin tolerance mutant strain Aspergillus niger AA120. The mutant A. niger AA120 was obtained by initially atmospheric pressure plasma at room temperature (ARTP) mutagenesis and then tannin gradient domestication. ARTP experiments showed that a “double-saddle” shape of survival rate curve was achieved, and a positive mutation rate of 63.6% was reached by setting the implantation time of mutagenesis to 100 s. In contrast to the original stain at the presence of 20.0 g/L tannin in the medium, the selected mutant A. niger AA120 exhibits an increase of biomass by 43.76% to 32.9 g/L, and citric acid production capacity by 20.34% to 130.8 g/L, with 8% (w/w) of inoculation quantity, an initial pH of 6.2 and shaking speed of 250 r/min. In this work, we present a referable method for the mutagenesis screening of the A. niger, and the application of acorn starch as a new raw material for the development of the citric acid industry.

Background Plant microbe-interactions contribute in mitigating abiotic environmental stresses in plants. Salinity stress is one of major factor in reducing agricultural productivity. Recently, the use of endophytic fungi has proved as one of the approaches that can help plant growth under salt stress. Therefore, the objective of this study was to isolate halotolerant endophytic fungi and elevate their potential to mitigate salt stress in Vigna radiata. Methodology Endophytic fungi were isolated from asymptomatic parts of Vachellia nilotica and screened for plant growth-promoting attributes such as IAA production, phosphate solubilization, siderophore production, and halotolerance. Based on growth-promoting characteristics and halotolerance, Aspergillus niger VN2 was selected and colonized in V. radiata . The colonized plants were exposed to different salt concentrations (150 mM, 200 mM, and 250 mM NaCl) to evaluate the effect of A. niger VN2 in mitigating salt stress. The effects of A. niger VN2 colonization on physiological, biochemical, and molecular parameters were assessed. Results In the present study, an endophytic fungus Aspergillus niger VN2 isolated from Vachellia nilotica exhibited good plant growth promotion properties and halotolerance. A. niger VN2 produced IAA (148.32 ± 2.34 µg/ml IAA), solubilized phosphate, and produced hydroxamate type siderophore (72.66% SU). It also exhibited ACC deaminase ability (134.40 ± 5.45µmolα-ketobutyrate/h/mg protein), and could tolerate up to 15% NaCl. Colonization of A. niger VN2 in V. radiata enhanced salt tolerance, and resulted in increased root and shoot length, biomass, leaf number, chlorophyll content, relative water content, and protein content in salt stressed plants. DPPH scavenging and endogenous IAA levels also increased in treated plants. Oxidative stress parameters viz. proline, electrolyte leakage, and malondialdehyde, were found to decrease in VN2 colonized plants. Fluorescent microscopy studies revealed VN2 colonized plants showed increased cell survival and lowered glutathione and hydrogen peroxide under salt stress. Comet assay was used for determining the genoprotective effect of A. niger VN2. Colonization of A. niger VN2 reduced DNA tail length, % tail DNA, tail moment, and olive tail moment in plants exposed to salt stress. The difference in biochemical molecules viz. protein, carbohydrates, lipid, and nucleic acid in colonized and non-colonized plants under salt stress was revealed by FT-IR spectroscopy and validated by PCA, which showed that A. niger VN2 mitigated salt-induced changes, as colonized samples clustered closely under both conditions. Conclusion From the current study, it can be concluded that colonization of endophytic fungus A. niger VN2 promotes plant growth and can mitigate salt stress in V. radiata by regulating oxidative stress.

Ochratoxin A (OTA) is a mycotoxin found in several agricultural commodities. Produced by Aspergillus spp., it is nephrotoxic and hepatotoxic and can be carcinogenic. Preventive measures are preventing fungal growth and OTA production. In this study, fungal strains (Rhizopus oryzae, Lichtheimia ramosa, Aspergillus westerdijkiae, Aspergillus niger, Aspergillus tamarii, Aspergillus sp., and Aspergillus fumigatus) isolated from coffee beans were identified for their abilities to inhibit the growth of Aspergillus ochraceus, Aspergillus westerdijkiae, Aspergillus carbonarius, and Aspergillus niger, and OTA production. All fungi strains tested were able to inhibit growth of the four Aspergillus species and OTA production, where A. niger showed the best results in both tests. L. ramosa showed the lowest growth-reducing potential, while the other fungal strains had a growth-reducing potential higher than 70% against all Aspergillus species tested. Regarding OTA production, L. ramosa and Aspergillus sp. completely inhibited the mycotoxin production by A. ochraceus and non-toxigenic strain A. niger completely inhibited OTA production by A. niger. Our findings indicate that the strains tested can be used as an alternative means to control growth of OTA-producing fungi and production of the mycotoxin in coffee beans.

The filamentous fungi Aspergillus niger and Hypocrea jecorina (Trichoderma reesei) have been the subject of many studies investigating the mechanism of transcriptional regulation of hemicellulase- and cellulase-encoding genes. The transcriptional regulator XlnR that was initially identified in A. niger as the transcriptional regulator of xylanase-encoding genes controls the transcription of about 20-30 genes encoding hemicellulases and cellulases. The orthologous xyr1 (xylanase regulator 1-encoding) gene product of H. jecorina has a similar function as XlnR, although at points, the mechanisms seems to be different. Specifically in H. jecorina, the interaction of Xyr1 and the co-regulators Ace1 and Ace2 in the regulation of transcription of xylanases and cellulases has been studied. This paper describes the similarities and differences in the transcriptional regulation of expression of hemicellulases and cellulases in A. niger and H. jecorina.

In recent years, due to an expansion of antibiotic-resistant microorganisms, there has been growing interest in biodegradable and antibacterial polymers that can be used in selected biomedical applications. The present work describes the synthesis of antimicrobial polylactide-copper alginate (PLA–ALG–Cu2+) composite fibers and their characterization. The composites were prepared by immersing PLA fibers in aqueous solution of sodium alginate, followed by ionic cross-linking of alginate chains within the polylactide fibers with Cu(II) ions to yield PLA–ALG–Cu2+ composite fibers. The composites, so prepared, were characterized by scanning electron microscopy (SEM), UV/VIS transmittance and attenuated total reflection Fourier-transform infrared spectroscopy ATR-FTIR, and by determination of their specific surface area (SSA), total/average pore volumes (through application of the 5-point Brunauer–Emmett–Teller method (BET)), and ability to block UV radiation (determination of the ultraviolet protection factor (UPF) of samples). The composites were also subjected to in vitro antimicrobial activity evaluation tests against colonies of Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria and antifungal susceptibility tests against Aspergillus niger and Chaetomium globosum fungal mold species. All the results obtained in this work showed that the obtained composites were promising materials to be used as an antimicrobial wound dressing.