Distribution, characteristics of extracellular polymeric substances of Phanerochaete chrysosporium under lead ion stress and the influence on Pb removal.

The distribution, characteristics of extracellular polymeric substances (EPS) of Phanerochaete chrysosporium under Pb2+ stress and the influence on Pb removal were investigated. Polysaccharides was found to be the main composition in both soluble EPS (SEPS) and bounded EPS (BEPS). More polysaccharides and protein in BEPS were detected with the increased Pb2+ concentration. The ratio of Pb amount distributed in BEPS to the total Pb removed by the fungal biomass gradually decreased from 91.66 to 61.27% in group with 50 mg/L of initial Pb2+, but kept at about 35% or 25% in groups with higher Pb2+. It implies that BEPS played a certain role in the lead removal process, and the role of BEPS was relatively more important in the removal of lower concentration of Pb2+ and in the initial period of Pb removal. With FTIR analysis and Pb2+ adsorption experiment, more effective functional groups and better Pb2+ adsorption capacity was demonstrated in BEPS than in SEPS. SEM-EDS analysis demonstrated that part of Pb immobilized in BEPS was in the form of Pb precipitation. The increased molecular weight in SEPS and more polysaccharides in BEPS were probably beneficial for the adhesion of Pb precipitation.

Phanerochaete chrysosporium strain B-22, a nematophagous fungus parasitizing Meloidogyne incognita.

The root-knot nematode Meloidogyne incognita has a wide host range and it is one of the most economically important crop parasites worldwide. Biological control has been a good approach for reducing M. incognita infection, for which many nematophagous fungi are reportedly applicable. However, the controlling effects of Phanerochaete chrysosporium strain B-22 are still unclear. In the present study we characterized the parasitism of this strain on M. incognita eggs, second-stage juveniles (J2), and adult females. The highest corrected mortality was 71.9% at 3 × 108 colony forming units (CFU) mL-1 and the estimated median lethal concentration of the fungus was 0.96 × 108 CFU mL-1. Two days after treatment with Phanerochaete chrysosporium strain B-22 eggshells were dissolved. A strong lethal effect was noted against J2, as the fungal spores developed in their body walls, germinated, and the resulting hyphae crossed the juvenile cuticle to dissolve it, thereby causing shrinkage and deformation of the juvenile body wall. The spores and hyphae also attacked adult females, causing the shrinkage and dissolution of their bodies and leakage of contents after five days. Greenhouse experiments revealed that different concentrations of the fungal spores effectively controlled M. incognita. In the roots, the highest inhibition rate for adult females, juveniles, egg mass, and gall index was 84.61%, 78.91%, 84.25%, and 79.48%, respectively. The highest juvenile inhibition rate was 89.18% in the soil. Phanerochaete chrysosporium strain B-22 also improved tomato plant growth, therefore being safe for tomato plants while effectively parasitizing M. incognita. This strain is thus a promising biocontrol agent against M. incognita.

Antimicrobial efficacy and mechanisms of silver nanoparticles against Phanerochaete chrysosporium in the presence of common electrolytes and humic acid.

In this study, influences of cations (Na+, K+, Ca2+, and Mg2+), anions (NO3-, Cl-, and SO42-), and humic acid (HA) on the antimicrobial efficacy of silver nanoparticles (AgNPs)/Ag+ against Phanerochaete chrysosporium were investigated by observing cell viability and total Ag uptake. K+ enhanced the antimicrobial toxicity of AgNPs on P. chrysosporium, while divalent cations decreased the toxicity considerably, with preference of Ca2+ over Mg2+. Impact caused by a combination of monovalent and divalent electrolytes was mainly controlled by divalent cations. Compared to AgNPs, however, Ag+ with the same total Ag content exhibited stronger antimicrobial efficacy towards P. chrysosporium, regardless of the type of electrolytes. Furthermore, HA addition induced greater microbial activity under AgNP stress, possibly originating from stronger affinity of AgNPs over Ag+ to organic matters. The obtained results suggested that antimicrobial efficacy of AgNPs was closely related to water chemistry: addition of divalent electrolytes and HA reduced the opportunities directly for AgNP contact and interaction with cells through formation of aggregates, complexes, and surface coatings, leading to significant toxicity reduction; however, in monovalent electrolytes, the dominating mode of action of AgNPs could be toxic effects of the released Ag+ on microorganisms due to nanoparticle dissolution.

Toxicity of nanodiamonds to white rot fungi Phanerochaete chrysosporium through oxidative stress.

Nanodiamonds (NDs) are produced with large scale and applied in many areas, thus the environmental impacts and hazards of NDs should be systematically investigated. In this study, we evaluated the interaction between detonation NDs and white rot fungus Phanerochaete chrysosporium and the impact on the fungus decompositions activities. NDs did not influence the biomass gain of P. chrysosporium and the culture medium pH values. The mycelia of P. chrysosporium were destroyed upon the direct contact with NDs, while the rest retained the fibrous structure. Ultrastructural observations suggested that small aggregates of NDs seldom entered the fungus cells, but the break of cell wall and the loss of cytoplasm were induced by NDs. Under both optical and electron microscopes, the aggregation of colloidal ND particles was observed, which was the possible reason of low toxicity. High concentrations of NDs inhibited the laccase activity and manganese peroxidase activity of P. chrysosporium, which led to the decrease of decomposition activity for pollutants. Colloidal ND particles were not well dispersed in sawdust degradation evaluations, so no inhibitive effect was observed for wood degradation. The toxicological mechanism of NDs was assigned to oxidative stress. The results collectively suggested that NDs had low toxicity to white rot fungi and could be applied safely. The colloid dispersion/aggregation of nanoparticles in biological systems should be carefully considered during the design of safe nanomaterials.

The cytotoxicities in prokaryote and eukaryote varied for CdSe and CdSe/ZnS quantum dots and differed from cadmium ions.

The present study focused on the bioaccumulation and cytotoxicities of Cd2+, CdSe quantum dots (QDs) and CdSe/ZnS QDs in Escherichia coli (E. coli, represents prokaryotic system) and Phanerochaete chrysosporium (P. chrysosporium, represents eukaryotic system), respectively. Two types of QDs were characterized by transmission electron microscopy (TEM) and dynamic light scattering. The inductively coupled plasma optical emission spectrometer results showed that the bioaccumulation amounts of CdSe QDs by E. coli and P. chrysosporium were larger than those of CdSe/ZnS QDs due to the smaller particle size and less negative surface charges of CdSe QDs. Confocal microscopy and TEM results showed that there was an interaction between QDs and cells, and QDs have entered into the cells eventually, leading to the change of cell morphology. Plasma membrane fluidities and membrane H+-ATPase activities of E. coli and P. chrysosporium decreased gradually with the increasing concentrations of Cd2+, CdSe and CdSe/ZnS QDs. Results of the cell viabilities and intracellular reactive oxygen species levels indicated that the induced cytotoxicities were decreased as follows: CdSe QDs > CdSe/ZnS QDs > Cd2+. These findings suggested that the cytotoxicity of QDs was not only attributed to their heavy metal components, but also related to their nanosize effects which could induce particle-specific toxicity. The above results offer valuable information for exploring the cytotoxicity mechanism of QDs in prokaryote and eukaryote.

Phanerochaete chrysosporium as a model organism to assess the toxicity of municipal landfill leachate from Elazig, Turkey.

In order to evaluate the potential ecological risk and the toxic effect of landfill leachate (LL), Phanerochaete chrysosporium was exposed to LL and their biochemical response was observed by using antioxidant parameters. Phanerochaete chrysosporium, ME 446, was kept at 4 °C after being sub-cultured at 28 °C on Sabouraud Dextrose Agar (SDA). Superoxide dismutase (SOD), catalase (CAT) activities, and malaondialdehyde (MDA) and glutathione (GSH) levels of P. chrysosporium exposed to different dilution rates of leachate (1/10 and 1/20) for 24 and 96 h were analyzed by using the ELISA method. The physiochemical parameters such as pH, conductivity, total dissolved solids (TDS), dissolved oxygen (DO), chemical oxygen demand (COD) of leachate, and reference water were analyzed by using the YSI Professional Plus handheld multiparameter meter. In this study, SOD activities were decreased in the application groups compared with the Control Group at the 24th and 96th hours. CAT activities and GSH levels increased in the application groups compared with the Control Group at the 24th hour but decreased at the 96th hours. MDA levels increased in all of the application groups when compared with the Control Group for both 24 and 96 h. Different concentration of LL induces oxidative stress in P. chrysosporium, increased CAT activity and MDA levels, and decreased SOD activity and GSH levels.

Toxicity of perfluorooctane sulfonate on Phanerochaete chrysosporium: Growth, pollutant degradation and transcriptomics.

As a persistent organic pollutant listed in the Stockholm Convention, perfluorooctane sulfonate (PFOS) is extremely refractory to degradation under ambient conditions. Its potential ecotoxicity has aroused great concerns and research interests. However, little is known about the toxicity of PFOS on fungus. In this study, the white rot fungus Phanerochaete chrysosporium (P. chrysosporium) was adopted to assess the toxicity of PFOS in liquid culture. The addition of 100 mg/L PFOS potassium salt significantly decreased the fungal biomass by up to 76.4% comparing with un-amended control during the incubation period. The hyphostroma of P. chrysosporium was wizened and its cell membrane was thickened, while its vesicle structure was increased, based on the observation with scanning electron microscope (SEM) and transmission electron microscope (TEM). Nevertheless, the PFOS dosage of below 100 mg/L did not show a considerable damage to the growth of P. chrysosporium. The degradation of malachite green (MG) and 2,4-dichlorophenol (2,4-DCP) by P. chrysosporium was negatively affected by PFOS. At the initial dosage of 100 mg/L PFOS, the decolorization efficiency of MG and the degradation efficiency of 2,4-DCP decreased by 37% and 20%, respectively. This might be attributed to the inhibition of PFOS on MnP and LiP activities. The activities of MnP and LiP decreased by 20.6% and 43.4%, respectively. At a high dosage PFOS (100 mg/L), P. chrysosporium could show a high adsorption of MG but lose its pollutant degradation ability. Transcriptome analysis indicated that PFOS contamination could lead to the change of gene expression in the studied white rot fungus, and the genes regulating membrane structure, cell redox process, and cell transport, synthesis and metabolism were impacted. Membrane damage and oxidative damage were the two main mechanisms of PFOS' toxicity to P. chrysosporium.

Alleviation of heavy metal and silver nanoparticle toxicity and enhancement of their removal by hydrogen sulfide in Phanerochaete chrysosporium.

Hydrogen sulfide (H2S), an important cellular signaling molecule, plays vital roles in mediating responses to biotic/abiotic stresses. Influences of H2S on metal removal, cell viability, and antioxidant response of Phanerochaete chrysosporium upon exposure to heavy metals and silver nanoparticles (AgNPs) in the present study were investigated. An enhancement in Pb(ΙΙ) removal with an increase in concentration of the H2S donor sodium hydrosulfide (NaHS) was observed, and the maximum removal efficiencies increased by 31% and 17% under 100 and 200 mg/L Pb(ΙΙ) exposure, respectively, in the presence of 500 µM NaHS. Application of 500 µM NaHS increased the cell viability by 15%-39% under Pb(II) stress (10-200 mg/L) with relative to the untreated control. Increase in total Ag uptake and cell survival was also elicited by NaHS in a concentration-dependent manner under AgNP stress. Meanwhile, activities of superoxide dismutase and catalase were significantly enhanced with the introduction of NaHS under stresses of Pb(II), Cd(II), Cu(II), Zn(II), Ni(II), and AgNPs. The inhibition in lipid peroxidation and oxidative stress was observed in P. chrysosporium cells exposed to these toxicants following NaHS pretreatment, which could be attributed to the upregulation in antioxidant enzymes. The results obtained suggest that H2S can alleviate heavy metals and AgNP-induced toxicity to P. chrysosporium and improve the removal efficiency of these toxicants from wastewater.

Genotoxicity effects of Phanerochaete chrysosporium against harmful algal bloom species by micronucleus test and comet assay.

Algal blooms and toxins have become serious ecological problems. White-rot fungi have been demonstrated to be a feasible means of control, but the genotoxicity mechanisms involved have not been reported. In this study, Cryptomonas obovata FACHB-1301, Oscillatoria sp. FACHB-1083, and Scenedesmus quadricauda FACHB-507 were co-cultured with Phanerochaete chrysosporium under optimal conditions of 250 mg-l at 25 °C with DO 7.0 mg-l for 1, 3, 5 and 7 d. Compared to the control groups, the values for tadpoles exposed to algae treated with Phanerochaete chrysosporium were only increased from 1.95 ± 0.09, 2.78 ± 0.08 and 2.37 ± 0.13 to 2.45 ± 0.07, 3.56 ± 0.08 and 2.54 ± 0.10, and the frequency of nuclear anomalies reached 6.45 ± 0.06, 11.14 ± 0.05 and 7.85 ± 0.10 to 7.68 ± 0.08, 13.12 ± 0.06 and 8.57 ± 0.12 in the experimental groups after 7 d. What's more, the tail lengths were only increased to 36.77 ± 0.54, 41.58 ± 0.78 and 35.38 ± 0.66, and the comet length reached 55.67 ± 0.68, 68.56 ± 0.85 and 51.43 ± 0.82. The results demonstrated that Phanerochaete chrysosporium effectively decreased genotoxicity effects in Fejervarya multistriat tadpoles. These results could provide new ideas for inhibiting water blooms, and lay a theoretical foundation for promoting the deepening of water eutrophication.

Oak extractive-induced stress reveals the involvement of new enzymes in the early detoxification response of Phanerochaete chrysosporium.

Extensive evidence showed that the efficiency of fungal wood degradation is closely dependent on their ability to cope with the myriad of putative toxic compounds called extractives released during this process. By analysing global gene expression of Phanerochaete chrysosporium after short oak extractive treatment (1, 3 and 6 h), we show that the early molecular response of the fungus concerns first mitochondrial stress rescue followed by the oxidation and finally conjugation of the compounds. During these early responses, the lignolytic degradative system is not induced, rather some small secreted proteins could play an important role in cell protection or signaling. By focusing on the functional characterization of an hitherto uncharacterized glutathione transferase, we show that this enzyme interacts with wood molecules suggesting that it could be involved in the detoxification of some of them, or act as a scavenger to prevent their cytosolic toxicity and favour their transport.

Toxicity of carbon nanotubes to white rot fungus Phanerochaete chrysosporium.

Carbon nanotubes (CNTs) are widely used in diverse areas with increasing annual production, thus the environmental impact of CNTs needs thorough investigation. In this study, we evaluated the effect of pristine multi-walled CNTs (p-MWCNTs) and oxidized multi-walled CNTs (o-MWCNTs) on white rot fungus Phanerochaete chrysosporium, which is the decomposer in carbon cycle and also has many applications in environmental remediation. Both p-MWCNTs and o-MWCNTs had no influence on the dry weight increase of P. chrysosporium and the pH value of culture system. The fibrous structure of P. chrysosporium was disturbed by p-MWCNTs seriously, while o-MWCNTs had litter influence. The ultrastructural changes were more evident for P. chrysosporium exposed to p-MWCNTs and only p-MWCNTs could penetrate into the cell plasma. The chemical composition of P. chrysosporium was nearly unchanged according to the infrared spectra. The laccase activity was suppressed by p-MWCNTs, while o-MWCNTs showed stimulating effect. The decoloration of reactive brilliant red X-3B was not affected by both CNT samples. However, serious inhibition of wood degradation was observed in the p-MWCNTs exposed groups, suggesting the potential threat of CNTs to the decomposition of carbon cycle. The implication to the environmental risks and safe applications of carbon nanomaterials is discussed.

Differential behaviors of silver nanoparticles and silver ions towards cysteine: Bioremediation and toxicity to Phanerochaete chrysosporium.

Potential transformations of silver nanoparticles (AgNPs) upon interaction with naturally ubiquitous organic ligands in aquatic environments influence their transport, persistence, bioavailability, and subsequent toxicity to organisms. In this study, differential behaviors of AgNPs and silver ions (Ag+) towards cysteine (Cys), an amino acid representative of thiol ligands that easily coordinate to Ag+ and graft to nanoparticle surfaces, were investigated in the aspects of bioremediation and their toxicity to Phanerochaete chrysosporium. Total Ag removal, 2,4-dichlorophenol (2,4-DCP) degradation, extracellular protein secretion, and cellular viability were enhanced to some extent after supplement of various concentrations of cysteine under stress of AgNPs and Ag+. However, an obvious decrease in total Ag uptake was observed after 5-50 µM cysteine addition in the groups treated with 10 µM AgNPs and 1 µM Ag+, especially at a Cys:Ag molar ratio of 5. More stabilization in uptake pattern at this ratio was detected under Ag+ exposure than that under AgNP exposure. Furthermore, in the absence of cysteine, all Ag+ treatments stimulated the generation of reactive oxygen species (ROS) more significantly than high-dose AgNPs did. However, cysteine supply under AgNP/Ag+ stress aggravated ROS levels, albeit alleviated at 100 µM Ag+, indicating that the toxicity profiles of AgNPs and Ag+ to P. chrysosporium could be exacerbated or marginally mitigated by cysteine. The results obtained were possibly associated with the lability and bioavailability of AgNP/Ag+-cysteine complexes.

Effects of cadmium on calcium homeostasis in the white-rot fungus Phanerochaete chrysosporium.

Due to the widespread application of white-rot fungi for the treatment of pollutants, it's crucial to exploit the special effects of pollutants on the microbes. Here, we studied the effects of cadmium on calcium homeostasis in the most studied white-rot fungus Phanerochaete chrysosporium. The response of P. chrysosporium to cadmium stress is concentration-dependent. A high concentration of cadmium caused the release of calcium from P. chrysosporium, while a hormesis effect was observed at a lower cadmium concentration (10 µM), which resulted in a significant increase in calcium uptake and reversed the decrease in cell viability. Calcium (50 µM) promoted cell viability (127.2% of control), which reflects that calcium can protect P. chrysosporium from environmental stress. Real-time changes in the Ca2+ and Cd2+ fluxes of P. chrysosporium were quantified using the noninvasive microtest technique. Ca2+ influx decreased significantly under cadmium exposure, and the Ca2+ channel was involved in Ca2+ and Cd2+ influx. The cadmium and/or calcium uptake results coupled with the real-time Ca2+ and Cd2+ influxes microscale signatures can enhance our knowledge of the homeostasis of P. chrysosporium with respect to cadmium stress, which may provide useful information for improving the bioremediation process.

Cadmium-induced stress response of Phanerochaete chrysosporium during the biodegradation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47).

Cd-induced stress response of Phanerochaete chrysosporium during the biodegradation of BDE-47 was investigated in this study, with the goal of elucidating the tolerance behavior and the detoxification mechanisms of P. chrysosporium to resist the Cd stress in the course of BDE-47 biodegradation, which has implications for expanding the application of P. chrysosporium in the bioremediation of Cd and BDE-47 combined pollution. The results suggested that single BDE-47 exposure did not induce obvious oxidative stress in P. chrysosporium, but coexistent Cd significantly triggered ROS generation, both intracellular ROS level and H2O2 content showed positive correlation with Cd concentration. The activities of SOD and CAT were enhanced by low level of Cd (≤ 1 mg/L), but Cd of higher doses (＞1 mg/L) depressed the expression of these two antioxidant enzymes at the later exposure period (3-5 days). The intracellular content of GSH along with GSH/GSSG ratio also exhibited a bell-shaped response with a maximum value at Cd of 1 mg/L. Furthermore, Cd-induced ROS generation resulted in the lipid peroxidation, as indicated by a noticeable increment of MDA content found after 3 days. Moreover, the study also indicated that Cd less than 1 mg/L promoted the production of extracellular protein and quickened the decrease of pH value in the medium, while excessive Cd (＞1 mg/L) would lead to inhibition. These findings obtained demonstrated that P. chrysosporium had a certain degree of tolerance to Cd within a specific concentration range via regulating the antioxidant levels, inducing the synthesis of extracellular protein as well as stimulating the production of organic acids, and 1 mg/L is suggested to be the tolerance threshold of this strains under Cd stress during BDE-47 biodegradation.

FTIR as an easy and fast analytical approach to follow up microbial growth during fungal pretreatment of poplar wood with Phanerochaete chrysosporium.

Since the determination of the fermentation kinetics is one of the main challenges in solid state fermentation, the quantitative measurement of biomass growth during microbial pretreatment by FTIR spectroscopy in Attenuated Total Reflectance mode was evaluated. Peaks at wave numbers of 1651 cm-1 and 1593 cm-1 showed to be affected during pretreatment of poplar wood particles by Phanerochaete chrysosporium MUCL 19343. Samples with different microbial biomass fractions were obtained from two different experiments, i.e., shake flask and fixed-bed reactor experiments. The glucosamine concentration was compared to the normalized absorbance ratio of the 1651 cm-1 to 1593 cm-1 peak, measured by FTIR-ATR, and resulted in a linear relationship. The application of a normalized absorbance ratio in function of time provided a graph that was similar to the microbial growth curve. Application of FTIR in ATR mode to follow-up kinetics during solid state fermentation seems to be a fast and easy alternative to laborious measurement techniques, such as glucosamine determination.

Silver ion-enhanced particle-specific cytotoxicity of silver nanoparticles and effect on the production of extracellular secretions of Phanerochaete chrysosporium.

This study investigated the influence of silver ions (Ag+) on the cytotoxicity of silver nanoparticles (AgNPs) in Phanerochaete chrysosporium and noted the degree of extracellular secretions in response to the toxicant's stress. Oxalate production was elicited with moderate concentrations of 2,4-dichlorophenol (2,4-DCP) and AgNPs reaching a plateau at 10 mg/L and 10 µM, respectively. Increased oxalate accumulation was accompanied by higher activities of manganese peroxidase (MnP) and lignin peroxidase (LiP). However, the secretion of oxalate, MnP and LiP was significantly inhibited owing to Ag+ incorporation into AgNP solution. Production of extracellular polymeric substances (EPS) significantly elevated with an increase in 2,4-DCP concentrations; however, after 24 h of exposure to 100 mg/L 2,4-DCP, an obvious decrease in EPS occurred, indicating that part of EPS could be consumed as carbon and energy sources to ameliorate biological tolerance to toxic stress. Furthermore, AgNP-induced "particle-specific" cytotoxicity was substantially enhanced with additional Ag+ as evidenced by its significant negative impact on cellular growth, plasma membrane integrity, and morphological preservation compared with AgNPs at equal Ag concentration.

Chloramine T induced oxidative stress and the response of antioxidant system in Phanerochaete chrysosporium.

In this study, the effect of chloramine T (Chl-T) on the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and glutathione S-transferase (GST); the levels of reduced (GSH) and oxidised glutathione (GSSG) and their ratios; and also membrane lipid peroxidation (LPO) levels in Phanerochaete chrysosporium were investigated in a dose- (0.25-1 mmol/L) and time-dependent (1.5-9 h) manner. The highest SOD activity was observed in 0.5 mmol/L Chl-T at 6th hour as 1.48-fold of its control. The observed highest level in CAT activities was 4.6-fold of control in 0.5 and 0.75 mmol/L at the 6th hour. The GSH levels that were over the control showed decreasing tendency from the beginning of incubation, except 0.25 mmol/L. In contrast with GSH level variations, GSSG levels reached 10.0-fold of its control by showing increasing tendency with the increases in concentration and time. While the GSH/GSSG ratios were over the control at 0.25 mmol/L during all incubation, they fell under the control values at the earlier hours of incubation with the increasing concentrations of Chl-T. Glutathione-related enzymes GSH-Px, GR and GST were also induced with Chl-T treatment, and the highest activities were 3.29-, 7.5- and 6.56-fold of their controls, respectively. On the other hand, the increases in LPO levels with increasing concentration and time up to 5.27-fold of its control showed that the inductions observed in antioxidant system could not prevent the Chl-T-based oxidative stress.

Transcriptome analysis reveals novel insights into the response to Pb exposure in Phanerochaete chrysosporium.

Metals released into the environment continue to be of concern for human health. Using white-rot fungi as biosorbents for heavy metals removal is an attractive alternative owing to its good performance and low cost. However, the molecular mechanism underlying heavy metal tolerance in white-rot fungi has not yet been fully elucidated. This study identified and analyzed the lead (Pb)-induced transcriptional changes in Phanerochaete chrysosporium, a well-known heavy metal hyperaccumulating white-rot fungus. The results confirmed its outstanding ability in Pb tolerance and effective defense system. By comparative analysis of gene expression profiles obtained from cDNA-amplified fragment length polymorphism (cDNA-AFLP), we isolated 43 transcript-derived fragments (TDFs) differentially regulated by Pb exposure in P. chrysosporium, and 23 TDFs presented significant similarities to genes encoding known or putative proteins which belong to different functional categories involving ion binding, energy and carbohydrate metabolism, and signal transduction. The detailed characterization of these Pb-responsive genes was presented and the expression patterns of some interesting genes were validated by quantitative RT-PCR. This work provides the first evidence of Pb-responsive genes along with their putatively functional annotations in P. chrysosporium, which may help to understand the mechanism underlying heavy metal accumulation and tolerance in P. chrysosporium.

Lead-induced oxidative stress and antioxidant response provide insight into the tolerance of Phanerochaete chrysosporium to lead exposure.

The present work investigated the effect of lead (Pb) on the growth, metal accumulation, oxidative stress, and antioxidant response in Phanerochaete chrysosporium, which is a well-known hyperaccumulating species for heavy metal with appreciable bioaccumulation capacity. Results revealed that P. chrysosporium exhibited a good ability in Pb accumulation and tolerance over a concentration range of 50-100 mg L-1 Pb. The removal rate of Pb decreased with the increasing levels of Pb and reached a maximum of 91.3% at 50 mg L-1. Both extracellular adsorption and intracellular bioaccumulation contributed to the removal of Pb, with the maximum of 123.8 mg g-1 and 162.5 mg g-1 dry weight, respectively. Pb may exert its toxicity to P. chrysosporium by impairing oxidative metabolism, as evidenced by the enhanced accumulation of hydrogen peroxide (H2O2) and lipid peroxidation product malonaldehyde (MDA). P. chrysosporium evolved an antioxidant system by elevating the activity of superoxide dismutase (SOD) and the level of reduced glutathione (GSH) in response to Pb stress, whereas decreasing the activities of catalase (CAT) and peroxidase (POD). Moreover, Pearson correlation analysis demonstrated a good correlation between oxidative stress biomarkers and enzymatic antioxidants. The preset work suggested that P. chrysosporium exhibited an outstanding accumulation of Pb and tolerance of Pb-induced oxidative stress by the effective antioxidant defense mechanism.

Manganese-enhanced degradation of lignocellulosic waste by Phanerochaete chrysosporium: evidence of enzyme activity and gene transcription.

Lignolytic fungi initiate lignocellulose decay by producing extracellular oxidative enzymes. For better understanding the enzymatic degradation of lignocellulose by white-rot fungi, we investigated the effect of manganese on the organic matter loss, manganese peroxidase (MnP) activity, and manganese peroxidase gene (mnp) transcription levels during solid-state fermentation of rice straw with Phanerochaete chrysosporium. The results showed that the addition of manganese improved MnP activity and made it reach the peak earlier, promoted fungal growth at the early period (0-9 days), and enhanced the degradation of lignocellulosic waste. The total organic matter loss had a good correlation with fungal biomass during 30 days of cultivation, and manganese amendment promoted the ability of P. chrysosporium to degrade lignocellulose. Quantitative real-time RT-PCR revealed the differential expression of mnp1, mnp2, and mnp3: manganese amendment increased the transcription of mnp1 and mnp2 but not mnp3. The results indicated that manganese stimulated mnp transcription levels and played a post-transcriptional role in MnP production. These findings provide opportunity of development in enzymatic degradation of lignocellulosic waste by P. chrysosporium amended with manganese.