A preliminary study of the applicability of sweet potatoes for mycological fat production

Summary For mycological fat production,Aspergillus nidulans andPenicillium lilacinum were grown on media made up of crushed and boiled sweet potatoes. Mycelial mats containing a fair amount of fat were obtained, namely, 15 % in case ofAspergillus and 24 % in case ofPenicillium. Media containing an external supply of glucose gave rise to increase in percentage fat in mycelium, but the amount of mycelium and consequently the total fat content decreased.Addition of sodium nitrate gave heavier mycelial mats but the total fat content could not be raised.Addition of potassium phosphate or magnesium sulphate or both to the sweet potato medium gave rise to heavier mycelial mats but with lower fat content.     

Growth and fat formation of Aspergillus oryzae and Aspergillus terreus on enzyme-hydrolyzed sweet potatoes

Two fungi, namely,Aspergillus oryzae andAspergillus terreus, have been grown on enzyme-hydrolyzed sweet potato medium either as such or supplemented with an external source of nitrogen in the form of ammonium carbonate, sodium nitrate, or asparagine. Hydrolysis alone promoted carbohydrate uptake, growth as well as fat formation to a remarkable extent in both fungi.Addition of an external supply of nitrogen to the hydrolyzed media increased further carbohydrate absorption which continued until the potato media were almost completely depleted; on unhydrolysed potato media, appreciable amounts of carbohydrates always remained unutilized. It also accelerated the rate of building up so that the dry mycelium increased by more than 4 times in some cases. Fat formation was consequently remarkably enhanced specially in the presence of ammonium carbonate or asparagine.     

Keratinolytic fungi of wadi Qena in Egypt

Forty-six soil samples collected from different sites of wadi Qena were examined for keratinophilic fungi using the hair baiting technique. Thirty-two species in addition to one variety of each ofA. nidulans andA. flavus which belong to eighteen genera were recovered.Aspergillus, Chrysosporium, Penicillium, Microsporum andFusarium were the most frequent genera developed from baited soils.     

NUT1, a major nitrogen regulatory gene inMagnaporthe grisea, is dispensable for pathogenicity

NUT1, a gene homologous to the major nitrogen regulatory genesnit-2 ofNeurospora crassa andareA ofAspergillus nidulans, was isolated from the rice blast fungus,Magnaporthe grisea. NUT1 encodes a protein of 956 amino acid residues and, likenit-2 andareA, has a single putative zinc finger DNA-binding domain. Functional equivalence ofNUT1 toareA was demonstrated by introducing theNUT1 gene by DNA-mediated transformation into anareA loss-of-function mutant ofA. nidulans. The introducedNUT1 gene fully complemented theareA null mutation, restoring to the mutant the ability to utilize a variety of nitrogen sources. In addition, the sensitivity ofAspergillus NUT1 transformants to ammonium repression of extracellular protease activity was comparable to that of wild-typeA. nidulans. Thus,NUT1 andareA encode functionally equivalent gene products that activate expression of nitrogen-regulated genes. A one-step gene disruption strategy was used to generatenutl ^– mutants ofM. grisea by transforming a rice-infecting strain with a disruption vector in which a gene for hygromycin B phosphotransferase (Hyg) replaced the zinc-finger DNA-binding motif ofNUT1. Of 31 hygromycin B (hyg B)-resistant transformants shown by Southern hybridization to contain a disruptedNUT1 gene (nut1::Hyg), 26 resulted from single-copy replacement events at theNUT1 locus. Althoughnut1 ^– transformants ofM. grisea failed to grown on a variety of nitrogen sources, glutamate, proline and alanine could still be utilized. This contrasts withA. nidulans where disruption of the zinc-finger region ofareA prevents utilization of nitrogen sources other than ammonium and glutamine. The role ofNUT1 and regulation of nitrogen metabolism in the disease process was evaluated by pathogenicity assays. The infection efficiency ofnut1 ^– transformants on susceptible rice plants was similar to that of the parental strain, although lesions were reduced in size. These studies demonstrate that theM. grisea NUT1 gene activates expression of nitrogen-regulated genes but is dispensable for pathogenicity.     

TheAspergillus nidulans geneschsA andchsD encode chitin synthases which have redundant functions in conidia formation

We previously isolated three chitin synthase genes (chsA, chsB, andchsC) fromAspergillus nidulans. In the present work, we describe the isolation and characterization of another chitin synthase gene, namedchsD, fromA. nidulans. Its deduced amino acid sequence shows 56.7% and 55.9% amino acid identity, respectively, with Cal1 ofSaccharomyces cerevisiae and Chs3 ofCandida albicans. Disruption ofchsD caused no defect in cell growth or morphology during the asexual cycle and caused no decrease in chitin content in hyphae. However, double disruption ofchsA andchsD caused a remarkable decrease in the efficiency of conidia formation, while double disruption ofchsC andchsD caused no defect. Thus it appears thatchsA andchsD serve redundant functions in conidia formation.     

Nitrogen regulation in fungi

Nitrogen regulation has been extensively studied in fungi revealing a complex array of interacting regulatory genes. The general characterisation of the systems inAspergillus nidulans andNeurospora crassa shall be briefly described, but much of this paper will concentrate specifically on the recent molecular characterisation ofareA, the principle regulatory gene fromA. nidulans which mediates nitrogen metabolite repression. Three areas shall be explored in detail, firstly the DNA binding domain, which has been characterised extensively by both molecular and genetic analysis. Secondly we shall report recent analysis which has revealed the presence of related DNA binding activities inA. nidulans. Finally we shall discuss the mechanism by which the nitrogen state of the cell is monitored by theareA product, in particular localisation of the domain within theareA product which mediates the regulatory response within the protein.     

蒜头果内生真菌次生代谢产物抑制人类致病菌活性的研究

蒜头果是我国特有的单种属稀有树种,为了进一步开发利用蒜头果树皮内生真菌的抗菌活性化合物,该研究对来自蒜头果的植物内生真菌(白黄笋顶孢霉、哈茨木霉、大棘黑团孢、枝状枝孢菌、斑污拟盘多毛孢、赭绿青霉、淡紫紫孢菌、朱黄青霉、Xenoacremonium recifei、Xylaria feejeensis)进行液体培养,10 d后回收培养液并用乙酸乙酯萃取获得初提物,采用抑菌圈法检测蒜头果内生真菌初提物抑菌活性,同时测定了最低抑菌浓度(MIC)。结果表明:白黄笋顶孢霉、大棘黑团孢、枝状枝孢菌、斑污拟盘多毛孢、赭绿青霉、淡紫紫孢菌均有抑菌活性,大棘黑团孢、斑污拟盘多毛孢、淡紫紫孢菌的初提物均对缓慢芽孢杆菌、无乳链球菌和藤黄微球菌有明显抗菌活性,最低抑菌浓度在1.562 5~6.25 mg·m L~(-1)之间。这说明蒜头果树皮内生真菌的次生代谢产物具有抗菌活性,各内生真菌次生代谢产物的抗菌效果不同。     

Effect of pH and organic matter on the toxicity of heavy metals to growth of some fungi

Increasing the pH from 5 to 9 decreased the toxicity of mercuric chloride, zinc sulfate, lead nitrate, copper sulfate and nickel chloride toward the growth ofAspergillus flavus, Penicillium chrysogenum, Cunninghamella echinulata, Myrothecium verrucaria andPhoma humicola. On the other hand, the toxicity of cadmium chloride was increased by the increasing pH. Also increasing the concentration of organic matter (peptone and yeast extract) from 0.5 to 1.5% induced a significant reduction in the toxicity of all heavy metals toward the growth of all test fungi.     

Amine Oxidases of Microorganisms

The amine oxidase was found to be formed in mycelia of fungi when they were grown on monoamines or diamines as sole nitrogen sources. The maximal formation of enzyme was observed in the initial stage of growth, then the enzyme disappeared semilogarithmically. Other sources of nitrogen, such as ammonia, nitrate, urea and amino acids, were fully inactive for the enzyme formation. Furthermore, ammonia repressed the enzyme formation by fungi. The amine oxidase of fungi resembled in substrate specificity the monoamine oxidase of animal tissues. The enzyme oxidized preferentially aliphatic monoamines of C₃–C₆. Agmatine and histamine were also oxidized but in lower rates. Benzylamine was well oxidized by the enzymes of Aspergillus niger and Penicillium chrysogenum, but not by the enzymes of Monascus anka and Fusarium bulbigenum. Polyamines were not oxidized by the fungal enzymes.     

Influence of nitrogen nutritions on asexual reproduction of five species Sphaeropsis sacc. in culture

Effect of fourteen different nitrogen sources on five species ofSphaeropsis i. e.S. cactinae, S. cycadis, S. jodhpurensis, S. muehlenbeckiae andS. punicae, obtained respectively from the infected parts ofCitrus medica, Cycas circinalis, Cordia gharaf, Muehlenbeckia platycladoes andPunica granatum was studied, under cultural conditions on Asthana and Hawker's Medium A by substituting its nitrogen with equal quantity of an other nitrogen source. All the present species reproduced well on potassium nitrate, sodium nitrate, ammonium sulphate and ammonium nitrate. None of the present species could grow on sodium nitrite. Out of all amino acids, no one was found to be excellent for the growth and sporulation of the present fungi. Most of the amino acids supported poor growth and sporulation of three of the five species ofSphaeropsis, S. cactinae, S. cycadis andS. punicae on L-asparagine, Glycine, L-cystine and L-alanine. Maximum and minimum pH for growth and sporulation ranged from 6.5 to 7.8 and 5.3 to 4.2 respectively. Decrease in adjusted pH was also observed for all the species on L-asparagine and DL-valine.     

Fungi in sediments of the sea of Japan and their biologically active metabolites

The most abundant marine fungi encountered in various regions of the Sea of Japan belong to the generaPenicillium, Aspergillus, Wardomyces, Trichoderma, Chrysosporium, andChaetomium. Facultative marine fungi of the generaScytalidium, Verticillium, andOidiodendron and obligate marine fungi of the genusDendryphiella are much less abundant. The composition of marine sediments and the anthropogenic load on them were found to influence the abundance and species diversity of fungi, as well as the occurrence of fungal strains producing hemolytically active substances. The biodiversity of mycobiota and the abundance of hemotoxin-producing fungi in marine sediments may be used to evaluate the anthropogenic load on marine biocenoses. Hemolytic compounds were produced by 57% of the fungi isolated from marine sediments. The hemolytic activity ofChaetomium spiculipilium was revealed in the fraction of the culture liquid containing extracellular fatty acids and pigments. The fatty acid composition of this marine fungus was determined.     

The effect of magnesium and phosphate on mycological fat formation from sweet potatoes

In an attempt to promote mycological fat formation from sweet potatoes, the sweet potato medium was supplemented with magnesium sulphate or sodium phosphate. The sweet potato medium itself was used either as such or after hydrolysis with acid or with enzyme. Two local fungi were used, namely,Aspergillus oryzae andA. terreus. Addition of magnesium or phosphate enhanced carbohydrate absorption from the external medium. This occurred to a remarkable extent in enzyme-hydrolysed sweet potato medium and when both factors were present. The presence of magnesium or phosphate suppressed fungal growth in acid-hydrolysed media particularly in case ofA. terreus. In untreated media either factor promoted growth ofA. oryzae but suppressed that ofA. terreus.     

TheAspergillus nidulans geneschsA andchsD encode chitin synthases which have redundant functions in conidia formation

We previously isolated three chitin synthase genes (chsA, chsB, andchsC) fromAspergillus nidulans. In the present work, we describe the isolation and characterization of another chitin synthase gene, namedchsD, fromA. nidulans. Its deduced amino acid sequence shows 56.7% and 55.9% amino acid identity, respectively, with Cal1 ofSaccharomyces cerevisiae and Chs3 ofCandida albicans. Disruption ofchsD caused no defect in cell growth or morphology during the asexual cycle and caused no decrease in chitin content in hyphae. However, double disruption ofchsA andchsD caused a remarkable decrease in the efficiency of conidia formation, while double disruption ofchsC andchsD caused no defect. Thus it appears thatchsA andchsD serve redundant functions in conidia formation.     

Extracellular mannanases and galactanases from selected fungi

Summary Eight thermophilic fungi were tested for production of mannanases and galactanases. Highest mannanase activities were produced byTalaromyces byssochlamydoides andTalaromyces emersonii. Mannanases from all strains tested were induced by locust bean gum except in the case ofThermoascus aurantiacus, where mannose had a greater inducing effect. Locust bean gum was also the best inducer of -mannosidase and galactanase except in the case ofT. emersonii where galactose was a better inducer of both these enzymes. Highest mannanase activity was produced byTalaromyces species when peptone was used as nitrogen source whereas sodium nitrate promoted maximum production of this enzyme byThielavia terrestris andT. aurantiacus. The pH optima of mannanases from the thermophilic fungi were in the range 5.0–6.6 and contrasted with the low pH optimum (3.2) of the enzyme fromAspergillus niger. Galactanases had pH optima in the range 4.3–5.8. The mannanase fromT. emersonii and the galactanase fromT. terrestris were most thermostable, each retaining 100% activity for 3 h at 60°C.     

ThePenicillium chrysogenum andAspergillus nidulans wetA developmental regulatory genes are functionally equivalent

Aspergillus nidulans andPenicillium chrysogenum are related fungi that reproduce asexually by forming multicellular conidiophores and uninucleate conidia. InA. nidulans, spore maturation is controlled by thewetA (AwetA) regulatory gene. We cloned a homologous gene (PwetA) fromP. chrysogenum to determine if spore maturation is regulated by a similar mechanism in this species. ThePwetA andAwetA genes are similar in structure and functional organization. The inferred polypeptides share 77% overall amino acid sequence similarity, with several regions having > 85% similarity. The genes also had significant, local sequence similarities in their 5 flanking regions, including conserved binding sites for the product of the regulatory geneabaA.PwetA fully complemented anA. nidulans wetA deletion mutation, demonstrating thatPwetA and its 5 regulatory sequences function normally inA. nidulans. These results indicate that the mechanisms controlling sporulation inA. nidulans andP. chrysogenum are evolutionarily conserved.     

Based on biochemical and physiological behavior,where isAspergillus egyptiacus better placed?

Physiological and biochemical properties were tested in 45 isolates ofAspergillus egyptiacus (16 isolates),Emericella nidulans (16) andAspergillus versicolor (13). The three fungal species exhibited common and similar features. The big similarity betweenA. egyptiacus andE. nidulans was greater than betweenA. egyptiacus andA. versicolor. It included the inability to produce base either from sodium citrate or lactic acid media, growth at 45 °C (thermophilicity), and production of very similar pigmentations onAspergillus flavus andparasiticus agar.A. egyptiacus is therefore better placed in theAspergillus nidulans-Emericella assemblage.     

Microbiological Synthesis of Fat: THE EFFECTS OF VARYING PH, TEMPERATURE, NITROGEN, INCUBATION PERIOD, AND SUGAR CONCENTRATION ON FAT-PRODUCING MOULDS

1. A more detailed study has been made of the influence of thesefactors on fat formation by Aspergillus nidulans, Penicilliumspinulosum, and Penicillium javanicum. 2. The effect of halving the glucose, while keeping the ammoniumnitrate concentration constant, lowered the yield of fat onsugar used in A. nidulans and P. spinulosum but not in P. javanicumcultures. 3. Keeping the same N: C ratio and raising the glucose concentrationfrom ro to 20 per cent. showed that to per cent. glucose wasmore efficiently converted to fat by A. nidulans and P. javanicum. 4. The iodine values of the extracted fats were higher, in general,with increased length of incubation. Low ammonium nitrate concentrations,however, tended to give low iodine values. 5. The results have been applied on a larger scale by growthin Roux bottles, Glaxo flasks, and a flat stainless-steel tank.     

Colonization ofRetama raetam seeds by fungi and their significance in seed germination

Examination by scanning electron microscopy and incubation on potato-dextrose agar medium showed that dry seeds ofRetama raetam were externally free of fungi. When planted in sandy loam soil, the seeds become colonized with eleven soil-borne fungal species. The fungi were isolated on cellulose agar, pectin agar and lignin agar media.Aspergillus flavus, A. niger, A. fumigatus, Penicillium capsolatum andFusarium oxysporum had broad occurrence and were recovered on all the three media. The production of hydrolytic enzymes by the isolated fungi depends on the substrate and species.Penicillium capsolatum, P. spinulosum andA. niger had wide enzymatic amplitude and they were able to produce cellulolytic, pectolytic and lignolytic activities on corresponding substrates as well as on seed-coat-containing media. The lignolytic activities of the isolated species exceptChaetomium bostrychodes andTrichoderma viride were enhanced by applying the seed-coat materials as C- source rather than lignin. SoakingR. raetam seeds in culture filtrates of most of the fungi grown on seed-coat-supplemented media induced a pronounced and distinct stimulating effect on seed germination. The most effective filtrates were those ofP. capsolatum, P. spinulosum andSporotrichum pulverulentum.