Mycelial Pigmentation Research Articles

Biocontrol efficacy of Pseudomonas mediterranea PVCT 3C against Plenodomus tracheiphilus: In vitro and in planta mechanisms at early disease stages

In this study, we investigated the biocontrol activity of the P. mediterranea strain PVCT 3C against Mal secco, a severe disease of citrus caused by the vascular fungus Plenodomus tracheiphilus. In vitro, bacterial diffusible compounds, volatile organic compounds and culture filtrates produced by PVCT 3C reduced the mycelial growth and conidial germination of P. tracheiphilus, also affecting the mycelial pigmentation. The application of bacterial suspensions by leaf-spraying before the inoculation with the pathogen on plants of the highly susceptible species sour orange and lemon led to an overall reduction in incidence and disease index, above all during the early disease stage. PVCT 3C genome was subjected to whole-genome shotgun sequencing to study the molecular mechanisms of action of this strain. In silico annotation of biosynthetic gene clusters for secondary metabolites revealed the presence of numerous clusters encoding antimicrobial compounds (e.g. cyclic lipopeptides, hydrogen cyanide, siderophores) and candidate novel products. During the asymptomatic disease phase (seven days post-inoculation), bacterial treatments interfered with the expression of different fungal genes, as assessed with an NGS and de novo assembly RNA-seq approach. These results suggest that P. mediterranea PVCT 3C or its secondary metabolites may offer a potential effective and sustainable alternative to contain P. tracheiphilus infections via integrated management.

Morphological characterization, pathogenicity screening, and molecular identification of Fusarium spp. isolates causing post-flowering stalk rot in maize.

Post flowering stalk rot (PFSR) of maize caused by the Fusarium species complex is a serious threat to maize production worldwide. The identification of Fusarium species causing PFSR based on morphology traditionally relies on a small set of phenomic characteristics with only minor morphological variations among distinct Fusarium species. Seventy-one isolates were collected from 40 sites in five agro-climatic zones of India to assess the diversity of Fusarium spp. associated with maize crops showing symptoms of PFSR in the field. To investigate the pathogenicity of Fusarium spp. causing PFSR sixty isolates were toothpick inoculated between the first and second node at 55 days after sowing during the tassel formation stage of the crop in Kharif (Rainy season), and Rabi (Winter season) season field trials. Ten most virulent Fusarium isolates, based on the highest observed disease index, were identified by homology and phylogenetic analyses of partial sequences of the translation elongation factor 1 α (Tef-1α). Based on morphological traits such as mycelial growth patterns and mycelial pigmentation, Fusarium isolates were divided into nine clusters. The isolates were judged to be virulent based on their ability to decrease seedling vigour in in-vivo situations and high disease severity in field experiments. Pathogenicity test during the Kharif season showed 12 isolates with virulent disease symptoms with a mean severity ranging between 50 to 67 percent disease index (PDI) whereas in Rabi season, only five isolates were considered virulent, and the mean severity ranged between 52 to 67 PDI. Based on pathological characterization and molecular identification, 10 strains of Fusarium species namely, Fusarium acutatum (2/10), Fusarium verticillioides (Syn. Gibberella fujikuroi var. moniliformis) (7/10), Fusarium andiyazi (2/10) recorded the highest diseases index. All these species are part of the Fusarium fujikuroi species complex (FFSC). The distribution of virulent isolates is specific to a geographical location with a hot humid climate. Increased knowledge regarding the variability of Fusarium spp. responsible for PFSR of maize occurring across wide geographical locations of India will enable more informed decisions to be made to support the management of the disease, including screening for resistance in maize-inbred lines.

Discovery of dual PKS involved in sclerotiorin biosynthesis in Penicillium meliponae using genome mining and gene knockout.

Fungi of the genus Penicillium section Sclerotiora have as their main characteristic the presence of orange-pigmented mycelium, which is associated with sclerotiorin, a chlorinated secondary metabolite of the azaphilone subclass of polyketides. Sclerotiorin presents anti-diabetes, antioxidant, anti-inflammatory, anti-Alzheimer, antiviral, and antimicrobial activities, which has always attracted the attention of researchers worldwide. During our ongoing search for azaphilone-producing Amazonian fungi, the strain of Penicillium MMSRG-058 was isolated as an endophyte from the roots of Duguetia stelechantha and showed great capacity for producing sclerotiorin-like metabolites. Using multilocus phylogeny, this strain was identified as Penicillium meliponae. Moreover, based on the genome mining of this strain through the reverse approach, a cluster of putative biosynthetic genes (BGC) responsible for the biosynthesis of sclerotiorin-like metabolites (scl cluster) was identified. The knockout of the sclA (highly reducing PKS) and sclI (non-reducing PKS) genes resulted in mutants with loss of mycelial pigmentation and terminated the biosynthesis of sclerotiorin-like metabolites: geumsanol B, chlorogeumsanol B, 7-deacetylisochromophilone VI, isochromophilone VI, ochrephilone, isorotiorin, and sclerotiorin. Based on these results, a biosynthetic pathway was proposed considering the homology of BGC scl genes with the azaphilone BGCs that have already been functionally characterized.

Molecular Analysis of the Genes Responsible for Catalysing Intracellular Steps of Aurofusarin Biosynthesis in Fusarium culmorum

HIGHLIGHTS • Molecular analysis of aurofusarin biosynthesis in F. culmorum. • Mycelial pigmentation depending on gene expression and aurofusarin accumulation. • Pigmentation variations depending on growth phase.

Characterization of Fusarium spp. causal agent of wilt in pecan

One of the limiting factors for pecan production is the incidence of disease caused by Fusarium spp. which are a threat to orchards in the south of the country. Therefore, the study aimed to confirm the pathogenicity and evaluate the morphophysiological and molecular characteristics of Fusarium spp. associated with pecan in Rio Grande do Sul and Paraná. For this, samples of symptomatic plant material were collected, and potentially pathogenic isolates were evaluated for pathogenicity, by immersing the roots of the plants in a spore suspension of Fusarium spp. In addition, the severity of the disease was assessed using a rating scale according to the symptoms expressed by the plants. The isolates were also analyzed for morphophysiological variability, through evaluations of mycelial growth, colony and aerial mycelium pigmentation, and characteristics of reproductive structures. Molecular characterization was performed which amplify the region of the 1-alpha elongation factor and sequencing. Nineteen isolates were obtained, which were considered pathogenic, however, there was variability in their aggressiveness and morphophysiological characteristics. In addition, the sequencing was used to identify different species. Therefore, species of Fusarium are responsible for the occurrence of wilt in pecan in southern Brazil.

Production, Bioprocessing and Anti-Proliferative Activity of Camptothecin from Penicillium chrysogenum, "An Endozoic of Marine Sponge, Cliona sp.", as a Metabolically Stable Camptothecin Producing Isolate.

Exploring the metabolic potency of fungi as camptothecin producers raises the hope of their usage as an industrial source of camptothecin, due to their short-life span and the feasibility of metabolic engineering. However, the tiny yield and loss of camptothecin productivity of fungi during storage and sub-culturing are challenges that counteract this approach. Marine fungi could be a novel source for camptothecin production, with higher yield and reliable metabolic sustainability. The marine fungal isolate Penicillium chrysogenum EFBL # OL597937.1 derived from the sponge “Cliona sp.” has been morphologically identified and molecularly confirmed, based on the Internal Transcribed Spacer sequence, exhibiting the highest yield of camptothecin (110 μg/L). The molecular structure and chemical identity of P. chrysogenum derived camptothecin has been resolved by HPLC, FTIR and LC-MS/MS analyses, giving the same spectroscopic profiles and mass fragmentation patterns as authentic camptothecin. The extracted camptothecin displayed a strong anti-proliferative activity towards HEP-2 and HCT-116 (IC50 values 0.33–0.35 µM). The yield of camptothecin was maximized by nutritional optimization of P. chrysogenum with a Plackett-Burman design, and the productivity of camptothecin increased by 1.8 fold (200 µg/L), compared to control fungal cultures. Upon storage at 4 °C as slope culture for 8 months, the productivity of camptothecin for P. chrysogenum was reduced by 40% compared to the initial culture. Visual fading of the mycelial pigmentation of P. chrysogenum was observed during fungal storage, matched with loss of camptothecin productivity. Methylene chloride extracts of Cliona sp. had the potency to completely restore the camptothecin productivity of P. chrysogenum, ensuring the partial dependence of the expression of the camptothecin biosynthetic machinery of P. chrysogenum on the chemical signals derived from the sponge, or the associated microbial flora. This is the first report describing the feasibility of P. chrysogenum, endozoic of Cliona sp., for camptothecin production, along with reliable metabolic biosynthetic stability, which could be a new platform for scaling-up camptothecin production.

Characteristic Observation of Cordyceps Militaris (L) Wild Type Strain from Five Oil Palm Plantation in Muara Wahau East Borneo

Cordycep militaris (L) is known in oil palm plantations as a natural enemy of nettle caterpillars. This fungus infects the caterpillars that descend down to become pupae around the palm circle, so that the pupae do not develop into imago and the pest's life cycle will be interrupted. This fungus is one of the 3 main entomopathogenic fungi used as bioinsecticides to control pests in oil palm plantations. In this study, the characteristics of C. militaris were observed from 5 oil palm plantations cultured in vitro using two types of media and two incubation methods. The results showed that there were mycelium pigmentation in nutrient-rich media Sabouraud Dextrose Agar plus Yeast extract (SDAY) when incubated with lighting. Only one of five mycelium cultures using SDAY media showed pigmentation on the no-light incubation method. Pigmentation did not occur in nutrient-poor media such as agar (WA), either incubated with lighting or with no-light. The growth of isolates was generally higher on SDAY media than on WA media. This study showed that C. militaris is a facultative phagotrophic fungus. The highest growth of isolates cultured on SDAY media incubated with lighting was found in isolates A and C, with colony diameter 90 mm, high mycelium density (+++) and hairy texture like cotton at the end of the 3rd week after inoculation. In the no-light incubation method, the highest growth was found in isolates B and C with colony diameter 90 mm, high mycelium density (+++) and hairy texture like cotton at the end of the 3rd week after inoculation. Isolates A and C showed high virulence potential to be used as bioinsecticides.

ОЦЕНКА ФУНГИЦИДНОЙ АКТИВНОСТИ ПРЕПАРАТОВ ДЛЯ ПРЕДПОСЕВНОЙ ОБРАБОТКИ СЕМЯН ОЗИМОЙ ПШЕНИЦЫ

The massive use of one-component fungicides has caused the problem of the emergence of resistant forms of phytopathogens. The development of multicomponent plant protection products is one of the ways of dealing with such a situation. The aim of the study is to determine the effectiveness of multicomponent chemical dressing agents in suppressing the most common fungal pathogens and seed infections in vitro. This work was performed in 2020 in the Federal Research Center for Biological Plant Protection (Krasnodar) in the laboratory of the creation of microbiological plant protection products and a collection of microorganisms. Fungi of the Fusarium, Microdochium, Bipolaris, Alternaria, Penicillium, Rhizoctonia, Septoria, Pyrenophora genera were used as test objects. The fungicidal activity of chemical preparations against economically significant phytopathogens causing root rot was evaluated in laboratory conditions by the method of serial dilutions followed by sowing on a nutrient medium. In addition, the effectiveness of the preparations was investigated by the method of treated seeds phytoexamination according to GOST 12044–93. The preparations, which included triazoles and phenylpyrroles, had the strongest inhibitory effect (100 %) on pathogens of Rhizoctonia, helminthosporiosis and septoria. The preparation containing compounds of the group of triazoles and strobilurins suppressed the growth of Rhizoctonia solani only. The preparations’ inhibitory effect on a number of phytopathogenic fungi was manifested in growth retardation, absence of aerial mycelium development and mycelium pigmentation. Concerning the causative agents of Fusarium root rot, the two-component preparations efficacy ranged from 51 % to 74.4 %; three-component one – from 42.9 % to 84.7 % depending on the species of the genus Fusarium. Presowing seed treatment made it possible to inhibit the growth of fungi of the genera Fusarium, Mucor, Aspergillus; significantly inhibit the development of the fungus Alternaria (spread in the experimental variant – 1.7 %, in the control variant – 46.7 %). From the data obtained, it can be concluded that multicomponent preparations based on triazoles and phenylpyrroles are highly effective in suppressing a wide range of phytopathogens and can be recommended for presowing seed treatment.

Influence of the 60 Hz Magnetic Field on the Airborne Microbial Distribution of Indoor Environments

The aim of this work was to analyze the effect of the magnetic field generated by the household appliances on the airborne microbial surrounding these equipment located on indoor environments with particular interest in the environmental fungi. A simultaneous environmental study was carried out in locals of three different geographical places of Havana, Cuba, which have televisions, computers and an electric generator. The air samples were made by a sedimentation method using Malt Extract Agar. The concentration of total aerobic mesophilic as well as fungi and yeasts were determined in rainy and little rainy seasons by applying as factors: exposure time of dishes (5 to 60 min) and distance to the wall (0 and 1 m) at a height of 1 m above the floor. The predominant fungal genera were Cladosporium, Penicillium and Aspergillus. In the dishes that were placed at 0 and 0.5 m from the emitting sources were observed that some bacteria colonies formed inhibition halos, a great diversity of filamentous fungi and an increase in the mycelium pigmentation as well as the pigments excretion. In the rainy season, the highest amounts of fungi were obtained in all samples. In the little rain season the count of the Gram-negative bacilli increased three times the Gram-positive cocci.

Sirtuin SirD is involved in α-amylase activity and citric acid production in Aspergillus luchuensis mut. kawachii during a solid-state fermentation process

Sirtuins are understood to play a significant role in growth phase-dependent gene expression. In the study presented here, we examined the sirtuins in the white koji fungus, Aspergillus luchuensis mut. kawachii (Aspergillus kawachii), to examine their role in the regulation of amylolytic enzymes and citric acid production during solid-state culture (koji). Characterization of rice koji made using five sirtuin gene disruptants indicated that these genes are involved in the amylolytic activity and acidity of rice koji; the sirD disruptant in particular showed lower levels of acid-stable α-amylase activity and citric acid production per mycelial weight in koji compared to the control strain. The sirD disruptant also showed a change in mycelial pigmentation, and had higher sensitivity to cell wall biogenesis inhibitors such as calcofluor white and Congo red and reduced conidia formation. These results indicate that SirD is required for secondary metabolism, cell wall integrity, and conidial development. Cap analysis gene expression (CAGE) and quantitative RT-PCR analysis indicated that transcriptional changes were related to the characteristic phenotype of the sirD disruptant, including a reduced transcript level of the acid-stable α-amylase gene and a citric acid exporter in rice koji. These results indicate that SirD has a significant role in global transcriptional regulation, including the production of acid-stable α-amylase and citric acid, in A.kawachii during the solid-state fermentation process.

First Report of Leaf and Stem Spot on Common Bean Caused by Stemphylium lycopersici in China

Common bean (Phaseolus vulgaris L.) is one of the most economically important vegetable crops in China. In October 2018, leaf and stem spot symptoms were observed on P. vulgaris in Pozhuang County, Anqiu City, Shandong Province, China. The disease incidence ranged from 15 to 20%, causing large economic losses to growers. Lesions were initially small (1 to 2 mm in diameter), scattered, reddish-brown spots on leaves and stems. As the disease progressed, lesions expanded and merged, resulting in withering of the whole leaves and gradually drying of the whole plant. To isolate the pathogen, diseased tissue (5 × 5 mm) was cut from the margins of lesions and surface disinfected with 70% ethanol for 15 s followed by 0.1% mercuric dichloride for 2 min and then rinsed four to five times with sterile distilled water. The specimens were then transferred to potato dextrose agar plates and incubated at 28°C for 5 or 7 days. Nineteen fungal isolates with similar morphological characteristics were obtained. The colony of G9RS, a representative isolate, was white to brownish in obverse and deep red in reverse with a vivid red mycelial pigmentation that diffused into the culture medium. The conidia produced on potato carrot agar (PCA) as the standard medium were solitary, oblong, constricted at the main transverse septum, and measured 36.4 ± 7.3 × 16.5 ± 2.6 μm (n = 50). For molecular characterization, genomic DNA was extracted by CTAB (Niu et al. 2010), and sequences of the internal transcribed spacer (ITS) regions (White et al. 1990) and glyceraldehyde-3-phosphate dehydrogenase (GPD) genes were amplified from isolates using the primer pairs ITS1/ITS4 and gpdf/gpdr (Câmara et al. 2002), respectively. The ITS and GPD sequences of isolate G9RS were submitted to GenBank (MN386223 and MN393479, respectively). BLASTn analysis of the sequences showed 99% identity with Stemphylium lycopersici (KX858848 and KR911809). Phylogenetic analysis (MEGA 7) using the neighbor-joining algorithm showed that the current isolate was clustered with S. lycopersici isolates (NO 425 and EGS46-001). Based on morphological and molecular characteristics, the isolate G9RS was identified as S. lycopersici. A pathogenicity test was conducted on intact plants according to Koch’s postulates. Conidia were collected from 21-day-old PCA cultures grown at 28°C under black light blue irradiation (365 nm) with a 12-h light/dark cycle, suspended in sterilized distilled water at 1.0 × 10⁵ conidia/ml, and the conidial suspension applied to ten 50-day-old bean plants (3 ml/plant). Ten plants inoculated with sterile distilled water served as controls. All samples were incubated in a growth chamber at 28°C. After 8 to 10 days, inoculated plants developed symptoms similar to original diseased plants in the field, whereas control plants remained symptomless. The same fungus was successfully reisolated from inoculated leaves and reidentified based on morphology and molecular evidence. The assay was conducted twice. Although S. lycopersici has been reported to cause leaf spot symptoms on other hosts, such as lettuce (Liu et al. 2019), potato (Yang et al. 2018), eggplant (Yang et al. 2017), Sansevieria (Kee et al. 2018), and pepino (Nasehi et al. 2016), to our knowledge, this is the first report of leaf and stem spot on common bean in China. Because the common bean is one of the most intensively planted crops in Shandong, this pathogen could have serious economic impact and may warrant development of integrated management strategies.

Verticillium dahliae transcription factor VdFTF1 regulates the expression of multiple secreted virulence factors and is required for full virulence in cotton.

Fungal transcription factors (TFs) implicated in the regulation of virulence gene expression have been identified in a number of plant pathogens. In Verticillium dahliae, despite its agricultural importance, few regulators of transcription have been characterized. In this study, a T-DNA insertion mutant with significantly reduced virulence towards cotton was identified. The T-DNA was traced to VdFTF1, a gene encoding a TF containing a Fungal_trans domain. Transient expression in onion epidermal cells indicated that VdFTF1 is localized to the nucleus. The VdFTF1-deletion strains displayed normal vegetative growth, mycelial pigmentation and conidial morphology, but exhibited significantly reduced virulence on cotton, suggesting that VdFTF1 is required exclusively for pathogenesis. Comparisons of global transcription patterns of wild-type and VdFTF1-deletion strains indicated that VdFTF1 affected the expression of 802 genes, 233 of which were associated with catalytic processes. These genes encoded 69 potentially secreted proteins, 43 of which contained a carbohydrate enzyme domain known to participate in pathogenesis during infection of cotton. Targeted gene deletion of one VdFTF1-regulated gene resulted in significantly impaired vascular colonization, as measured by quantitative polymerase chain reaction, as well as aggressiveness and symptom severity in cotton. In conclusion, VdFTF1, which encodes a TF containing a Fungal_trans domain, regulates the gene expression of plant cell wall degradation enzymes in V. dahliae, which are required for full virulence on cotton.

The pleiotropic vegetative and sexual development phenotypes of Neurospora crassa arise from double mutants of the calcium signaling genes plc-1, splA2, and cpe-1.

We investigated phenotypes of the double mutants of the calcium (Ca2+) signaling genes plc-1, splA2, and cpe-1 encoding for a phospholipase C1 (PLC-1), a secretory phospholipase A2 (sPLA2), and a Ca2+/H+ exchanger (CPE-1), respectively, to understand the cell functions regulated by their genetic interactions. Mutants lacking plc-1 and either splA2 or cpe-1 exhibited numerous defects including reduced colonial growth, stunted aerial hyphae, premature conidiation on plates with delayed germination, inappropriate conidiation in submerged culture, and lesser mycelial pigmentation. Moreover, the ∆plc-1; ∆splA2 and ∆plc-1; ∆cpe-1 double mutants were female-sterile when crossed with wild type as the male parent. In addition, ∆plc-1, ∆splA2, and ∆cpe-1 single mutants displayed higher carotenoid accumulation and an increased level of intracellular reactive oxygen species (ROS). Therefore, the pleiotropic phenotype of the double mutants of plc-1, splA2, and cpe-1 suggested that the genetic interaction of these genes plays a critical role for normal vegetative and sexual development in N. crassa.

Effect of Various Compounds Blocking the Colony Pigmentation on the Aflatoxin B1 Production by Aspergillus flavus.

Aflatoxins and melanins are the products of a polyketide biosynthesis. In this study, the search of potential inhibitors of the aflatoxin B1 (AFB1) biosynthesis was performed among compounds blocking the pigmentation in fungi. Four compounds—three natural (thymol, 3-hydroxybenzaldehyde, compactin) and one synthetic (fluconazole)—were examined for their ability to block the pigmentation and AFB1 production in Aspergillus flavus. All compounds inhibited the mycelium pigmentation of a fungus growing on solid medium. At the same time, thymol, fluconazole, and 3-hydroxybenzaldehyde stimulated AFB1 accumulation in culture broth of A. flavus under submerged fermentation, whereas the addition of 2.5 μg/mL of compactin resulted in a 50× reduction in AFB1 production. Moreover, compactin also suppressed the sporulation of A. flavus on solid medium. In vivo treatment of corn and wheat grain with compactin (50 μg/g of grain) reduced the level of AFB1 accumulation 14 and 15 times, respectively. Further prospects of the compactin study as potential AFB1 inhibitor are discussed.

Factors affecting mycelium pigmentation and pathogenicity ofSclerotinia sclerotiorumon Valencia peanut

Sclerotinia sclerotiorum infects a broad range of plant hosts, and is typically identified by the production of white mycelium and black sclerotia on infected plants and culture. Isolates of S. sclerotiorum with darkly-pigmented mycelium have been reported on Valencia peanut in New Mexico and Texas. This study was conducted to determine the relationship between dark pigmentation in mycelium, oxalic acid production, and pathogenicity of S. sclerotiorum on Valencia peanut. A darkly-pigmented (SD) and a mutant, non-pigmented (SW) isolate of S. sclerotiorum were compared for vegetative growth on various growth media under different environmental conditions, and for pathogenicity on peanut. The SD isolate became darker in mycelium pigmentation as temperature increased beyond 20 °C and at pH between 5.0 and 6.0. Pigmentation in the SW isolate remained unaffected. Oxalic acid production did not increase in either SD or SW isolates when grown on media amended with pure oxalic acid or its precursor arabinose. The SD isolate caused peanut plant death and necrotic lesions on leaflets, while the SW isolate did not cause any symptoms. The differential behavior of SD and SW isolates in pathogenicity does not appear to be associated with mycelium pigmentation.

Similar Aggressiveness of Phenotypically and Genotypically Distinct Isolates of Sclerotinia sclerotiorum.

Understanding how Sclerotinia sclerotiorum aggressiveness varies among isolates may be useful for breeding programs aimed at developing common bean cultivars resistant to white mold. The aggressiveness of 20 S. sclerotiorum isolates collected in common bean fields from four Brazilian states was tested against two common bean genotypes (Pérola and A195) using two inoculation methods. The isolates were characterized using 10 microsatellite (SSR) loci, mycelial compatibility groups (MCGs), partial sequences of the oxaloacetate acetylhydrolase (OAH) gene, and morphological traits. Twenty SSR and seven OAH haplotypes, 10 MCGs, and high variability in colony morphology were found. One isolate was more aggressive when inoculated on plants of the genotype A195, but all other isolates had similar aggressiveness. Aggressiveness was not related with MCGs, SSR, OAH haplotypes, mycelial pigmentation, growth rate, or sclerotia production.

Comparison of corncob and corn using as fungal culture medium

Corn or maize is the most widely grown grain crop. It is very practical. It is used as staple food, major source of cooking oil and grown to feed for livestock. Starch from maize can be made into syrups plastics, fabrics, adhesives, and many other chemical products and also fermented and distilled to produce alcohol. This research aims to compare pigment synthetic of Neurospora sp., widely used as a model organism in genetics research, when use corn, dry corncob and potato dextrose agar as culture medium. After fully grow up, extracted mycelium pigment with 95% ethyl alcohol. Then measure the absorbance of the pigment by spectrophotometer at wavelength 450.5 nanometer. The results showed that the best growth of Neurospora cultured on dry corncob was sample which added water (for moisture) 90 % w/w. While the best growth of Neurospora cultured on corn was sample which added water only 15 % w/w. When compare the intensity of mycelium pigment, it was found that corncob is the best medium for pigment synthetic of Neurospora. Absorbance of pigment extract from mycelium culture on corncob was 0.64(diluted 5X). As the absorbance of pigment extract from mycelium culture on corn and PDA were only 0.34(diluted 5X) and 0.35(diluted 2X).Keywords: corn, corncob, fungal, medium.

Morphological changes and growth of filamentous fungi in the presence of high concentrations of PAHs.

In this study, we evaluated the effect of low and high molecular weight polycyclic aromatic hydrocarbons (PAHs), i.e., Phenanthrene, Pyrene and Benzo[a]pyrene, on the radial growth and morphology of the PAH-degrading fungal strains Aspergillus nomius H7 and Trichoderma asperellum H15. The presence of PAHs in solid medium produced significant detrimental effects on the radial growth of A. nomius H7 at 4,000 and 6,000 mg L−1 and changes in mycelium pigmentation, abundance and sporulation ability at 1,000–6,000 mg L−1. In contrast, the radial growth of T. asperellum H15 was not affected at any of the doses tested, although sporulation was observed only up to 4,000 mg L−1 and as with the H7 strain, some visible changes in sporulation patterns and mycelium pigmentation were observed. Our results suggest that fungal strains exposed to high doses of PAHs significantly vary in their growth rates and sporulation characteristics in response to the physiological and defense mechanisms that affect both pigment production and conidiation processes. This finding is relevant for obtaining a better understanding of fungal adaptation in PAH-polluted environments and for developing and implementing adequate strategies for the remediation of contaminated soils.

Comparison of Corncob and Corn Using as Fungal Culture Medium

The key factor of powerful scientific studies is experiment. This research studied how to use cereals and waste from it to achieve value. Corn or maize is the most widely grown grain crop. It is very practical. It is used as staple food, major source of cooking oil and grown to feed for livestock. Starch from maize can be made into syrups plastics, fabrics, adhesives, and many other chemical products and also fermented and distilled to produce alcohol. This research aims to compare pigment synthetic of Neurospora sp., widely used as a model organism in genetics research, when use corn, dry corncob and potato dextrose agar as culture medium. After fully grow up, extracted mycelium pigment with 95% ethyl alcohol. Then measure the absorbance of the pigment by spectrophotometer at wavelength 450.5 nanometer. The results showed that the best growth of Neurospora cultured on dry corncob was sample which added water (for moisture) 90% w/w. While the best growth of Neurospora cultured on corn was sample which added water only 15% w/w. When compare the intensity of mycelium pigment, it was found that corncob is the best medium for pigment synthetic of Neurospora. Absorbance of pigment extract from mycelium culture on corncob was 0.64(diluted 5X). As the absorbance of pigment extract from mycelium culture on corn and PDA were only 0.34(diluted 5X) and 0.35(diluted 2X).

Methionine biosynthesis is essential for infection in the rice blast fungus Magnaporthe oryzae.

Methionine is a sulfur amino acid standing at the crossroads of several biosynthetic pathways. In fungi, the last step of methionine biosynthesis is catalyzed by a cobalamine-independent methionine synthase (Met6, EC 2.1.1.14). In the present work, we studied the role of Met6 in the infection process of the rice blast fungus, Magnaporthe oryzae. To this end MET6 null mutants were obtained by targeted gene replacement. On minimum medium, MET6 null mutants were auxotrophic for methionine. Even when grown in presence of excess methionine, these mutants displayed developmental defects, such as reduced mycelium pigmentation, aerial hypha formation and sporulation. They also displayed characteristic metabolic signatures such as increased levels of cysteine, cystathionine, homocysteine, S-adenosylmethionine, S-adenosylhomocysteine while methionine and glutathione levels remained unchanged. These metabolic perturbations were associated with the over-expression of MgCBS1 involved in the reversed transsulfuration pathway that metabolizes homocysteine into cysteine and MgSAM1 and MgSAHH1 involved in the methyl cycle. This suggests a physiological adaptation of M. oryzae to metabolic defects induced by the loss of Met6, in particular an increase in homocysteine levels. Pathogenicity assays showed that MET6 null mutants were non-pathogenic on both barley and rice leaves. These mutants were defective in appressorium-mediated penetration and invasive infectious growth. These pathogenicity defects were rescued by addition of exogenous methionine and S-methylmethionine. These results show that M. oryzae cannot assimilate sufficient methionine from plant tissues and must synthesize this amino acid de novo to fulfill its sulfur amino acid requirement during infection.