Increase In Fungal Biomass Research Articles

Gene expression patterns and dynamics of the colonization of common bean (Phaseolus vulgaris L.) by highly virulent and weakly virulent strains of Fusarium oxysporum

The dynamics of root and hypocotyl colonization, and the gene expression patterns of several fungal virulence factors and plant defense factors have been analyzed and compared in the interaction of two Fusarium oxysporum f. sp. phaseoli strains displaying clear differences in virulence, with a susceptible common bean cultivar. The growth of the two strains on the root surface and the colonization of the root was quantitatively similar although the highly virulent (HV) strain was more efficient reaching the central root cylinder. The main differences between both strains were found in the temporal and spatial dynamics of crown root and hypocotyl colonization. The increase of fungal biomass in the crown root was considerably larger for the HV strain, which, after an initial stage of global colonization of both the vascular cylinder and the parenchymal cells, restricted its growth to the newly differentiated xylem vessels. The weakly virulent (WV) strain was a much slower and less efficient colonizer of the xylem vessels, showing also growth in the intercellular spaces of the parenchyma. Most of the virulence genes analyzed showed similar expression patterns in both strains, except SIX1, SIX6 and the gene encoding the transcription factor FTF1, which were highly upregulated in root crown and hypocotyl. The response induced in the infected plant showed interesting differences for both strains. The WV strain induced an early and strong transcription of the PR1 gene, involved in SAR response, while the HV strain preferentially induced the early expression of the ethylene responsive factor ERF2.

Selective alteration of soil food web components by invasive giant goldenrod Solidago gigantea in two distinct habitat types

Apart from relatively well‐studied aboveground effects, invasive plant species will also impact the soil food web. So far, most research has been focusing on primary decomposers, while studies on effects at higher trophic levels are relatively scarce. Giant goldenrod Solidago gigantea, native to North America, is a widespread and common invasive species in most European countries. We investigated its impact on plant communities and on multiple trophic levels of the soil food web in two contrasting habitats: riparian zones and semi‐natural grasslands. In 30 pairs of invaded and uninvaded plots, floristic composition, pH, fungal biomass and the densities of 11 nematode taxa were determined by using a quantitative PCR‐based method. In the two habitats, the invader outcompeted both rare and dominant plant species. Belowground, S. gigantea invasion reduced pH, increased overall fungal biomass as well as the density of a single lineage of fungivorous nematodes, the family Aphelenchoididae. The densities of two other, phylogenetically distinct lineages of fungivorous nematodes, Aphelenchidae and Diphtherophoridae, were unaffected by the local increase in fungal biomass. Apparently this plant species induces a local asymmetric boost of the fungal community, and only Aphelenchoididae were able to benefit from this invader‐induced change. The alternative explanation – the results are explained by a subtle, S. gigantea‐induced 0.1–0.2 units decrease of pH – seems unlikely, as pH optima for nematode taxa are relatively broad. Thus, apart from readily observable aboveground effects, the invasive plant species S. gigantea affects fungal biomass as well as a specific part of the fungivorous nematode community in a soil type‐independent manner.

Spatial and temporal dynamics of the colonization ofPinus radiatabyFusarium circinatum, of conidiophora development in the pith and of traumatic resin duct formation

· Fusarium circinatum causes pitch canker disease in a wide range of pine trees, including Pinus radiata, with devastating economic consequences. · To assess the spatial and temporal dynamics of growth of this pathogen in radiata pine, we examined the process of infection using both real-time PCR to quantify fungal biomass inside the plant host, and confocal microscopy using a green fluorescent protein (GFP)-tagged strain of F. circinatum. · Pathogen growth exhibited three distinct phases: an initial exponential increase in fungal biomass, concomitant with pathogen colonization of the cortex and phloem; a slowdown in fungal growth coincident with sporulating hyphae deep within the host; and stabilization of the fungal biomass when the first wilting symptoms appeared. The number of resin ducts in the xylem was found to increase in response to infection and the fungus grew inside both constitutive and traumatic resin ducts. · These results indicate that conidiation may contribute to the spatial or temporal dissemination of the pathogen. Moreover, the present findings raise the intriguing possibility that the generation of traumatic resin ducts may be of more benefit to the fungus than to the plant.

Biosorption and biodegradation of polycyclic aromatic hydrocarbons by Phanerochaete chrysosporium in aqueous solution

Biosorption and biodegradation of phenanthrene and pyrene by live and heat-killed Phanerochaete chrysosporium are investigated to elucidate the bio-dissipation mechanisms of polycyclic aromatic hydrocarbons (PAHs) in aqueous solution and its regulating factors. The effects of nutrient conditions (carbon source and nitrogen source concentrations), the co-existing Cu2+, and repeated-batch feed of PAHs on the biosorption and biodegradation are systematically studied. The removal of PAHs by dead bodies of P. chrysosporium is attributed to biosorption only, and the respective partition coefficients of phenanthrene and pyrene are 4040 and 17500 L/kg. Both biosorption and biodegradation contribute to the dissipation of PAHs by live P. chrysosporium in water. After a 3-d incubation, the removal percentage via biosorption are 19.71% and 52.21% for phenanthrene and pyrene, respectively. With the increase of the incubation time (3–40 d), biodegradation gradually increases from 20.40% to 60.62% for phenanthrene, and from 15.55% to 49.21% for pyrene. Correspondingly, the stored-PAHs in the fungal bodies decrease. Under the carbon-rich and nitrogen-limit nutrient conditions, the removal efficiency and biodegradation of phenanthrene and pyrene are significantly promoted, i.e. 99.55% and 92.77% for phenanthrene, and 99.47% and 83.97% for pyrene after a 60-d incubation. This phenomenon is ascribed to enhanced-biosorption due to the increase of fungal biomass under carbon-rich condition, and to stimulated-biodegradation under nitrogen-limit condition. For the repeated-batch feed of phenanthrene, the pollutant is continuously removed by live P. chrysosporium, and the contribution of biodegradation is enhanced with the repeated cycles. After 3 cycles, the biodegradation percentage is up to 90% with each cycle of a 6-d incubation.

Solubilization of phosphates in vitro by Aspergillus spp. and Penicillium spp.

Phosphorus (P) is one of the most important nutrients for plant development and in most Brazilian soils the content of this element is low and relatively available to plants. Phosphate-solubilizing microorganisms play an important role in supplying P to plants, because of their ability to provide insoluble phosphates, added or existing in the soil, by the processes of acidification, chelation and ion-exchange reactions. The objective of this study was to evaluate the capacity and potential of ten fungal isolates in solubilizing simple superphosphate (SSP) and mono-ammonium phosphate (MAP) in vitro, in four periods (1st, 4th, 7th and 10th days after inoculation). It was found that 90% of these isolates showed potential for solubilization of SSP and MAP on the seventh day of evaluation, with average values of 23% and 22% higher than control, respectively, with a reduction thereafter. This reduction can be attributed to the increase in fungal biomass, which results in enhanced uptake of soluble phosphate for growth. All isolates, except for the PSF 94, solubilized the two sources of phosphate on the 7th day, but the isolated PSF 28 in MAP, and PSF 220 in SSP, stood out from others by having the highest values of soluble P (84 and 56μgml−1, respectively). This is the first reported solubilization of single superphosphate and mono-ammonium phosphate in vitro by the Aspergillus and Penicillium species, demonstrating that these fungi can serve as phosphate-solubilizing these P sources, contributing to a better use of the SSP and MAP and reducing the cost of agricultural inputs and the impact caused by excess phosphorus.

Antrodia albida (Fr.) Donk (Higher Basidiomycetes) as a Source of Metabolites of Biotechnological Interest

The basidiomycete Antrodia albida was grown in different culture media to study the production of biomass and its active substances. A progressive increase in fungal biomass throughout the 30-day incubation period was observed. The extracts showed discrete antibacterial activity, and the chemical analysis by gas chromatography coupled with mass spectrometry revealed a total of 17 substances in the fungal extracts, including sugars and furanones.

Assessment of hot peppers for aflatoxin and mold proliferation during storage.

Aflatoxin contamination and mold proliferation in three hot pepper hybrids (Sky Red, Maha, and Wonder King) were studied during 5 months of storage at three temperatures (20, 25, and 30°C) and under different packaging conditions (low-density polyethylene bags and jute bags). The presence of aflatoxins in hot pepper samples was determined by high-performance liquid chromatography with a UV-Vis detector. Sampling for analysis of aflatoxins, total mold counts, and Aspergillus counts was carried out at 0, 50, 100, and 150 days of storage. Hot peppers packed in jute bags were more susceptible to aflatoxin contamination than those packed in polyethylene bags; aflatoxin concentrations were 75% higher in peppers stored in jute bags. The effect of storage temperature resulted in aflatoxin concentrations that were 61% higher in hot peppers stored at 25 and 30°C than in those stored at 20°C. Of the three pepper hybrids, Wonder King was more susceptible to aflatoxin contamination, with a maximum of 1.50 μg/kg when packed in jute bags and stored at 25°C for 150 days. However, no sample exceeded the maximum permitted level for total aflatoxins in spices established by European Union regulations (10 μg/kg). Total mold counts and Aspergillus counts increased with storage duration, but all counts were significantly lower in peppers stored in polyethylene bags. A gradual increase in temperature during prolonged storage of hot peppers in combination with aeration may be the main reasons for increases in fungal biomass and Aspergillus proliferation with the subsequent aflatoxin production.

Humus macro-morphology and soil microbial community changes along a 130-yr-old Fagus sylvatica chronosequence

We aimed to characterize humus macro-morphology and the associated soil microbial community within the unmodified litter (OL), the fragmented and humified layers (FH) and the organo-mineral (A) layer along a beech (Fagus sylvatica L.) forest chronosequence with four stand age-classes (15-, 65-, 95-, 130-yr-old) in Normandy, France. Humus macro-morphology was described with 36 quantitative and semi-quantitative variables. We measured microbial biomass N (Nmic), microbial N quotient (Nmic-to-Nt), fungal ergosterol, bacterial and fungal DNA using 16S and 18S rDNA real-time qPCR and evaluated the potential metabolic profile of heterotrophic bacteria within each soil layer and stand age-class. The log-transform ergosterol/fungal DNA ratio (EFR index) was used as an indicator related to active fungal biomass and the fungal/bacterial (F/B) ratio was calculated from qPCR results. There was a shift from mull (mainly dysmull) to moder humus forms along the chronosequence. While the Nmic did not change significantly, the Nmic-to-Nt decreased along the chronosequence in the OL layer. Ergosterol content increased in FH and A layers and the F/B ratio increased in the FH layer with increasing beech forest age. The EFR index was significantly higher in the OL and A layers of the oldest stands, whereas the highest EFR index in the FH layer occurred in the 15-yr-old stands. The functional diversity of heterotrophic bacteria was greater within OL and FH layers of 130-yr-old stands, but highest in the A layer of 15-yr-old stands while the Average Well Color Development remained stable for all soil layers. We found significant correlations between macro-morphology and microbial variables, especially between FH-based morphology and fungal biomass. Our main results are that beech forest maturation is accompanied by (1) an increase in fungal biomass in the FH layers and, (2) an increase in heterotrophic bacteria functional diversity in the organic layers. We have identified key macro-morphology variables that are good predictors of the structural and functional profile of the soil microbial community during beech forest development.

Effect of Biosurfactants on Laccase Production and Phenol Biodegradation in Solid-State Fermentation

The effects of two biosurfactants, tea saponin (TS) and rhamnolipid (RL), on the production of laccase and the degradation of phenol by P. simplicissimum were investigated in solid-state fermentation consisting of rice straw, rice bran, and sawdust. Firstly, the effects of phenol on the fermentation process were studied in the absence of surfactants. Then, a phenol concentration of 3mg/g in the fermentation was selected for detailed research with the addition of biosurfactants. The results showed that TS and RL at different concentrations had stimulative effects on the enzyme activity of laccase. The highest laccase activities during the fermentation were enhanced by 163.7%, 68.2%, and 23.3% by TS at concentrations of 0.02%, 0.06%, and 0.10%, respectively. As a result of the enhanced laccase activity, the efficiency of phenol degradation was also improved by both biosurfactants. RL caused a significant increase of fungal biomass in the early stage of the fermentation, while TS had an inhibitory effect in the whole process. These results indicated that RL could mitigate the negative effects of phenol on fungal growth and consequently improve laccase production and phenol degradation. TS was potentially applicable to phenol-polluted solid-state fermentation.

Analysis of early events in the interaction between Fusarium graminearum and the susceptible barley (Hordeum vulgare) cultivar Scarlett

A proteomic analysis was conducted to map the events during the initial stages of the interaction between the fungal pathogen Fusarium graminearum and the susceptible barley cultivar Scarlett. Quantification of fungal DNA demonstrated a sharp increase in fungal biomass in barley spikelets at 3 days after inoculation. This coincided with the appearance of discrete F. graminearum-induced proteolytic fragments of β-amylase. Based on these results, analysis of grain proteome changes prior to extensive proteolysis enabled identification of barley proteins responding early to infection by the fungus. In total, the intensity of 51 protein spots was significantly changed in F. graminearum-infected spikelets and all but one were identified. These included pathogenesis-related proteins, proteins involved in energy metabolism, secondary metabolism and protein synthesis. A single fungal protein of unknown function was identified. Quantitative real-time RT-PCR analysis of selected genes showed a correlation between high gene expression and detection of the corresponding proteins. Fungal genes encoding alkaline protease and endothiapepsin were expressed during 1-3 days after inoculation, making them candidates for generation of the observed β-amylase fragments. These fragments have potential to be developed as proteome-level markers for fungal infection that are also informative about grain protein quality.

Effects of tree species and N additions on forest floor microbial communities and extracellular enzyme activities

Forest nitrogen (N) retention and soil carbon (C) storage are influenced by tree species and their associated soil microbial communities. As global change factors alter forest composition, predicting long-term C and N dynamics will require understanding microbial community structure and function at the tree species level. Because atmospheric N deposition is increasing N inputs to forested ecosystems across the globe, including the northeastern US, it is also important to understand how microbial communities respond to added N. While prior studies have examined these topics in mixed-species stands, we focused on the responses of different tree species and their associated microbial communities within a single forest type – a northern hardwood forest in the Catskills Mountains, NY. Based on prior studies, we hypothesized that N additions would stimulate extracellular enzyme activities in relatively labile litters, but suppress oxidative enzyme activities in recalcitrant litters, and tested for independent tree species effects within this context. During the 2007 growing season (May–June), we measured enzyme activities and microbial community composition (using phospholipid fatty acid analysis - PLFA) of the forest floor in single-species plots dominated by sugar maple ( Acer saccharum ), yellow birch ( Betula alleghaniensis ), red oak ( Quercus rubra ), American beech ( Fagus grandifolia ) and eastern hemlock ( Tsuga canadensis ), species whose litters range from relatively labile to recalcitrant. Half the plots were fertilized with N by adding NH 4 NO 3 (50 kg ha −1 y −1 ) from 1997 to 2009. Non-metric multidimensional scaling (NMS) and multi-response permutation procedures (MRPP) were used to examine microbial community structure and relationship to enzyme activities. We found that in response to N additions, both microbial community composition and enzyme activities changed; however the strength of the changes were tree species-specific and the direction of these changes was and not readily predictable from prior studies conducted in mixed-species stands. For example, in contrast to other studies, we found that N additions caused a significant overall increase in fungal biomass that was strongest for yellow birch (24% increase) and weakest for sugar maple (1% increase). Contrary to our initial hypotheses and current conceptual models, N additions reduced hydrolytic enzyme activities in hemlock plots and reduced oxidative enzyme activity in birch plots, a species with relatively labile litter. These responses suggest that our understanding of the interactions between microbial community composition, enzyme activity, substrate chemistry, and nutrient availability as influenced by tree species composition is incomplete. NMS ordination showed that patterns in microbial community structure (PLFA) and function (enzyme activity) were more strongly influenced by tree species than by fertilization, and only partially agreed with the structure–function relationships found in other studies. This finding suggests that tree species-specific responses are likely to be important in determining the structure and function of northeastern hardwood forests in the future. Enhanced understanding of microbial responses to added N in single and mixed-species substrates with varying amounts of lignin and phenols may be needed for accurate predictions of future soil C and N dynamics.

Ageing effects of casts of Aporrectodea caliginosa on soil microbial community structure and activity

We studied the ageing of casts of the earthworm species Aporrectodea caliginosa in the field and their effects on soil microbial community structure and activity in a grassland soil. For this purpose, we sampled casts and the bulk soil (below and surrounding casts), 1 and 2 months after deposition of the casts. Discriminant and cluster analyses separated casts from soil samples, and revealed significant differences in microbial community structure in aged casts. There were no differences between soil below casts and surrounding soil samples. The overall microbial biomass and microbial activity were higher in casts than in soils. The same was true for the main groups of soil microbial communities, bacteria and fungi. Ageing of casts did not decrease the overall microbial biomass, and there was an unexpected increase in fungal biomass; however, ageing clearly decreased microbial activity. The effects of A. caliginosa on soil microbial communities in the grassland were strong, and contrary to our expectations, persisted over time. In fact, our data indicates that casts seem to function as isolated hot spots of microbial biomass and activity, with minimal interactions with soil.

Size-fractionated (1 → 3)-β- D-glucan concentrations aerosolized from different moldy building materials

Release of submicrometer-sized fungal fragments (< 1.0 μm) was discovered in earlier studies, which investigated the aerosolization of spores from moldy surfaces. However, the contribution of fungal fragments to total mold exposure is poorly characterized. The purpose of this study was to investigate the size-fractionated concentrations of particulate (1 → 3)-β- D-glucan and numbers of particles aerosolized from the surface of artificially mold-contaminated materials using a novel sampling methodology. Aspergillus versicolor and Stachybotrys chartarum were grown on malt extract agar and building materials (ceiling tiles and gypsum board) for one to six months. Fungal particles released from these materials were collected size-selectively by a newly developed Fragment Sampling System, and (1 → 3)-β- D-glucan in air samples was analyzed by Limulus Amebocyte lysate (LAL) assay. The concentrations of (1 → 3)-β- D-glucan varied from 0.4 × 10 0 to 9.8 × 10 2 ng m − 3 in the fragment size and from 1.0 × 10 1 to 4.7 × 10 4 ng m − 3 in the spore size range. Numbers of submicrometer-sized particles aerosolized from 6-month old cultures were always significantly higher that those from 1-month old ( P < 0.001). This can be attributed to increased dryness on the surface of material samples and an increase in fungal biomass over time. The average fragment to spore ratios both in particle numbers and (1 → 3)-β- D-glucan mass were higher for S. chartarum than for A. versicolor. The results indicate that long-term mold damage in buildings may lead to increased contribution of fragments to the total mold exposure. Therefore, the health impact of these particles may be even greater than that of spores, considering the strong association between numbers of fine particles and adverse health effects reported in other studies. Furthermore, the contribution of fragments may vary between species and appears to be higher for S. chartarum than for A. versicolor.

Microbial activity and quality changes during decomposition of Quercus ilex leaf litter in three Mediterranean woods

Changes in enzyme activities during litter decomposition provide diagnostic information on the dynamics of decay and functional microbial succession. Here we report a comparative study of enzyme activities involved in the breakdown of major plant components and of other key parameters (microbial respiration, fungal biomass, N, lignin and cellulose contents) in homogeneous leaf litter of Quercus ilex L. incubated in three evergreen oak woods in Southern Italy (Campania), differing for chemical and physical soil characteristics and microclimatic conditions. The results showed that the litter mass loss rates were similar in the three wood sites. Independently of the incubation sites, cellulase, xylanase and peroxydase activities showed seasonal variations with maximum and minimum levels in wet and dry periods, respectively, and this pattern closely matched microbial respiration. Activities of α- and β-amylase, instead, were high at the beginning of incubation and quickly decreased with decomposition progress because their substrate was rapidly depleted. Laccase activity, in contrast, was low at the beginning of incubation but after 6 months it increased significantly. The increase of laccase activity was correlated to an increase in fungal biomass, probably reflecting a major shift in the litter microbial community. As concerns quality changes, N and lignin content did not significantly change during decay. The cellulosic component started being degraded after about 6 months in the litter incubated in two of the three wood sites and from the start of decomposition in the third site. Apart from minor differences in the levels of certain enzyme activities, the data showed that the functional microbial succession involved in the decomposition of Q. ilex leaf litter did not change appreciably in response to differences in soil and microclimatic conditions in the incubation sites.

Transcriptome analysis of high-temperature adult-plant resistance conditioned by Yr39 during the wheat-Puccinia striiformis f. sp. tritici interaction.

Stripe rust [caused by Puccinia striiformis Westend. f. sp. tritici Eriks. (Pst)] is a destructive disease of wheat (Triticum aestivum L.) worldwide. High-temperature adult-plant (HTAP) resistance to stripe rust is race non-specific, inherited quantitatively and durable. Previously, we identified and mapped the single Yr39 HTAP stripe rust resistance gene in the spring wheat cultivar Alpowa, which was identified on chromosome 7BL and accounted for 64.2% of the variation in resistance. To identify transcripts associated with Yr39-mediated resistance, we selected two F(7 )recombinant inbred lines (RILs) from an 'Avocet S/Alpowa' cross that differed at the Yr39 locus to represent an incompatible (Yr39) and compatible (yr39) interaction with Pst. Using the Affymetrix Wheat GeneChip, we profiled the transcript changes occurring in flag leaves of these two RILs over a time-course after treatment with Pst urediniospores and mock-inoculation. This time-course study identified 99 induced transcripts that were classified as HTAP resistance-specific. The temporal pattern of transcript accumulation showed a peak at 48 h after infection, which was supported by microscopic observation of fungal development and quantitative PCR assays that showed a rapid increase in fungal biomass after this time in the compatible interaction. More than half (50.5%) of the annotated transcripts specifically induced during HTAP resistance were involved in defence and/or signal transduction, including R gene homologues and transcripts associated with pathogenesis-related protein production, phenylpropanoid biosynthesis and protein kinase signalling. This study represents the first transcript profiling of HTAP resistance to stripe rust in wheat, and we compare our results with other transcript studies of race-specific and race non-specific resistance.

Relationships between Fungal Biomass and Nitrous Oxide Emission in Upland Rice Soils under No Tillage and Cover Cropping Systems

The relationships between soil microbial properties and nitrous oxide emission were examined in upland soil under different tillage systems [no tillage (NT), rotary and plow tillage] and cover crop systems (fallow, cereal rye, and hairy vetch) in 2004 and 2005. Microbiological analyses included the determination of soil ergosterol as an indicator of fungal biomass, bacterial plate counting, and MPN estimations of ammonia oxidizers and denitrifiers. The combined practice of NT with rye-cover crop treatment increased fungal biomass but not bacterial populations in 0-10 cm deep soils. Such increase in fungal biomass was not found in 10-20 cm and 20-30 cm deep cover-cropped NT soil. The combined practice of NT with rye-cover cropping resulted in higher in situ N(2)O emission rates compared with rotary- and plow-till treatments. N(2)O flux was positively correlated with soil ergosterol content but not with denitrifier MPN and other soil chemical properties. These results suggested a significant contribution of fungi to N(2)O emission in cover-cropped NT soils.

Root exudates regulate soil fungal community composition and diversity.

Plants are in constant contact with a community of soil biota that contains fungi ranging from pathogenic to symbiotic. A few studies have demonstrated a critical role of chemical communication in establishing highly specialized relationships, but the general role for root exudates in structuring the soil fungal community is poorly described. This study demonstrates that two model plant species (Arabidopsis thaliana and Medicago truncatula) are able to maintain resident soil fungal populations but unable to maintain nonresident soil fungal populations. This is mediated largely through root exudates: the effects of adding in vitro-generated root exudates to the soil fungal community were qualitatively and quantitatively similar to the results observed for plants grown in those same soils. This effect is observed for total fungal biomass, phylotype diversity, and overall community similarity to the starting community. Nonresident plants and root exudates influenced the fungal community by both positively and negatively impacting the relative abundance of individual phylotypes. A net increase in fungal biomass was observed when nonresident root exudates were added to resident plant treatments, suggesting that increases in specific carbon substrates and/or signaling compounds support an increased soil fungal population load. This study establishes root exudates as a mechanism through which a plant is able to regulate soil fungal community composition.

Purification and Characterization of a Keratinase from a Feather-Degrading Fungus, Aspergillus flavus Strain K-03

A keratinolytie enzyme secreted by Aspergillus flavus K-03 cultured in feather meal basal medium (FMBM) containing 2% (w/v) chicken feather was purified and characterized. Keratinolytie enzyme secretion was the maximal at day 16 of the incubation period at pH 8 and 28°C. No relationship was detected between enzyme yield and increase of fungal biomass. The fraction obtained at 80% ammonium sulfate saturation showed 2.39-fold purification and was further purified by gel filtration in Sephadex G-100 followed by ion exchange chromatography on DEAE-Sephadex A-50, yielding an active protein peak showing 11.53-fold purification. Sodium dodeeyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and zymograms indicated that the purified keratinase is a monomeric enzyme with 31 kDa molecular weight. The extracellular keratinase of A. flavus was active in a board range of pH (7~10) and temperature (30°C~70°C) profiles with the optimal for keratinase activity at pH 8 and 45°C. The keratinase activity was totally inhibited by protease inhibitors such as phenylmethylsulfonyl fluoride (PMSF), iodoaeetie acid, and ethylenediaminetetraaeetate (EDTA) while no reduction of activity by the addition of dithiothreitol (DTT) was observed. N-terminal amino acid sequences were up to 80% homologous with the fungal subtilisins produced by Fusarium culmorum. Therefore, on the basis of these characteristics, the keratinase of A. flavus K-03 is determined to be subtilisins-like.

Trehalose synthesis in ectomycorrhizas – a driving force of carbon gain for fungi?

Trehalose synthesis in ectomycorrhizas – a driving force of carbon gain for fungi?

Endophyte production of reactive oxygen species is critical for maintaining the mutualistic symbiotic interaction between Epichloe festucae and Pooid grasses

Perennial ryegrass, tall fescue and meadow fescue infected with a noxA mutant defective in the ability to produce reactive oxygen species (ROS), had a stunted phenotype and showed premature senescence. Microscopic observations of leaf tissue from perennial ryegrass and tall fescue showed a lack of regulated growth of mutant hyphae in these tissues with increasedv branching, growth and vascular colonisation. However, the fungal phenotype of noxA-infected meadow fescue was very similar to the wild-type phenotype suggesting that an increase in fungal biomass and vascular bundle colonisation is not necessarily a requirement for host stunting. An alternative hypothesis to explain the stunting phenotype is a breakdown in normal signaling between endophyte and host that is ROS dependent. Keywords: Epichloë festucae, Lolium perenne, NoxA, NADPH oxidase, reactive oxygen species (ROS)