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PubMed1982

[Effect of pentachloronitrobenzene (PCNB) on the ultrastructure of Mucor mucedo and Phytophthora cactorum].

The effect of PCNB in various concentrations on the ultrastructure of Mucor mucedo and phytophthora cactorum was analyzed after an incubation period of 2 hours. The most striking effect in both fungi was a diffuse lysis of the internal structure of the mitochondria which differs markedly from the lysis induced by etridiazol (terrazol). Moreover an enlargement of the perinuclear space and an increased formation of vacuoles was observed. In Mucor mucedo, but not in Phytophthora cactorum a pathological thickening of the cell wall was observed. Although after 2 hours incubation with PCNB Phytophthora gave similar ultrastructural reactions in the mitochondria as Mucor, in growth experiments on agar dishes this species was 5-10 times less sensitive to PCNB compared to Mucor.

Fungi↗
PubMed1998

Lovastatin triggers an apoptosis-like cell death process in the fungus Mucor racemosus.

The filamentous dimorphic fungus Mucor racemosus possesses three ras genes, Mras1, 2, and 3, whose expression is correlated to morphogenesis of the fungus. Lovastatin, an indirect inhibitor of protein prenylation, altered the processing of MRas1 protein, blocked the accumulation of MRas3 protein, and caused the MRas1/p20 protein complex to disappear in M. racemosus. Concurrently it arrested sporangiospore germination, decreased growth rate, caused a loss of cell viability accompanied by cell shrinkage, increased cell density and cytoplasm condensation, and triggered DNA fragmentation, resulting in nucleosomes and nucleosome multimers. The specific morphological and biochemical events seen in Mucor cell death, particularly DNA fragmentation, resemble the best known characteristics of classical apoptosis in mammalian cells and prompted us to classify lovastatin-induced cell death as an apoptosis-like process. Lovastatin did not cause cell death in a leucine auxotroph of Mucor grown in YNB minimal medium, conditions which support only spherical growth during spore germination. Exogenous dibutyryl-cAMP initiated morphogenesis from hyphal (polar) growth to yeast-like (spherical) growth during spore germination and strongly prevented cell death which resulted from lovastatin treatment. Wortmannin added together with dibutyryl-cAMP showed a synergistic effect in the prevention of fungal cell death. These data suggest that the regulation of lovastatin-induced cell death in Mucor requires a signal transduction pathway(s) involving cAMP whose function is specific to a particular developmental stage.

Androstadienes↗
PubMed1989

Structure of a ribosomal protein gene in Mucor racemosus.

As an extension of our analysis of the translational apparatus of Mucor racemosus we have isolated a gene encoding a ribosomal protein of Mucor. Based on a method developed for S. cerevisiae, we identified by hybrid selection and in vitro translation a lambda-Charon 4A clone containing the genomic copy of a Mucor ribosomal protein. The gene consisted of two exons of 57 and 387 nucleotides. The two exons were separated by an 131 nucleotide intron. The processed transcript was 714 nucleotides in length and contained a 25 nucleotide untranscribed leader and an 114 nucleotide untranscribed 3'-end. The protein predicted from the nucleotide sequence contained 148 amino acids and exhibited 61% identity with the S19 ribosomal protein of Xenopus laevis. The promoter region of the gene contained sequences highly homologous to the RPG and Homol1 promoter elements found in S. cerevisiae. Southern blot analysis indicated that the Mucor genome contains three copies of this gene.

Amino Acid Sequence↗
PubMed1982

Polyuronide biosynthesis by cell-free extracts of Mucor rouxii.

Cell-free extracts from Mucor rouxii contain enzymes that catalyse the synthesis of uridine diphosphate glucuronic acid (UDPGlcA) from UDPglucose and the incorporation of glucuronic acid from UDPGlcA into polymer(s). Two different polyuronide fraction isolated from the cell walls of this fungus were used as primers. Mucoran, a heteropolymer, was much more efficient than mucoric acid, which is largely a homopolymer of D-glucuronic acid. The primer ability of native cell walls was comparable to that of mucoric acid. Most of the glucuronosyltransferase activity in the cell-free extract was found in a 20000 g particulate fraction. Optimum pH for polyuronide synthesis was 7.0. Mn2+ or Mg2+ stimulated incorporation of GlcA. The products synthesized from mucoric acid and mucoran primers were different and yielded different disaccharides upon hydrolysis.

Biopolymers↗
PubMed1989

Two different intrachain cAMP sites in the cAMP-dependent protein kinase of the dimorphic fungus Mucor rouxii.

cAMP sites of the cAMP-dependent protein kinase from the fungus Mucor rouxii have been characterized through the study of the effects of cAMP and of cAMP analogs on the phosphotransferase activity and through binding kinetics. The tetrameric holoenzyme, which contains two regulatory (R) and two catalytic (C) subunits, exhibited positive cooperativity in activation by cAMP, suggesting multiple cAMP-binding sites. Several other results indicated that the Mucor kinase contained two different cooperative cAMP-binding sites on each R subunit, with properties similar to those of the mammalian cAMP-dependent protein kinase. Under optimum binding conditions, the [3H]cAMP dissociation behavior indicated equal amounts of two components which had dissociation rate constants of 0.09 min-1 (site 1) and 0.90 min-1 (site 2) at 30 degrees C. Two cAMP-binding sites could also be distinguished by C-8 cAMP analogs (site-1-selective) and C-6 cAMP analogs (site-2-selective); combinations of site-1- and site-2-selective analogs were synergistic in protein kinase activation. The two different cooperative binding sites were probably located on the same R subunit, since the proteolytically derived dimeric form of the enzyme, which contained one R and one C component, retained the salient properties of the untreated tetrameric enzyme. Unlike any of the mammalian cyclic-nucleotide-dependent isozymes described thus far, the Mucor kinase was much more potently activated by C-6 cAMP analogs than by C-8 cAMP analogs. In the ternary complex formed by the native Mucor tetramer and cAMP, only the two sites 1 contained bound cAMP, a feature which has also not yet been demonstrated for the mammalian cAMP-dependent protein kinase.

Allosteric Regulation↗
PubMed1967

Mode of filamentous growth of Leucothrix mucor in pure culture and in nature, as studied by tritiated thymidine autoradiography.

Mode of growth of Leucothrix mucor filaments was measured by autoradiography with tritiated thymidine. Studies were performed on L. mucor in pure cultures in free suspension, as an epiphyte of pure cultures of the red alga Antithamnion sarniense, and as an epiphyte of red algae in the sea. Statistical analyses of the distribution of growing cells was done by use of the nonparametric One-Sample Runs Test and a Cluster analysis adapted from quadrat analyses of plant ecologists. No evidence of preferential growth at base or tip of L. mucor filaments was obtained in any of these studies. However, in nature, but not in the laboratory, there were regions of L. mucor filaments which were nongrowing or dormant. Such nongrowing regions could incorporate tritiated glucose.

Autoradiography↗
PubMed1962

Induction of yeast-like development in Mucor by carbon dioxide.

Bartnicki-Garcia, S. (Rutgers, The State University, New Brunswick, N. J.) and Walter J. Nickerson. Induction of yeastlike development in Mucor by carbon dioxide. J. Bacteriol. 84:829-840. 1962-Vegetative development of Mucor rouxii may follow either one of two patterns of morphogenesis (mold-yeast dimorphism), depending on the atmosphere of incubation. Under air or N(2), a filamentous (moldlike) growth developed, commonly followed by fragmentation of hyphae into spherical cells (arthrospores). Introduction of CO(2) into an anaerobic atmosphere induced development of spherical, budding yeastlike cells. Anaerobically, a pCO(2) of 0.3 atm or higher produced a purely yeastlike development. Presence of oxygen annulled the effect of CO(2) On germination, spores gave rise directly to either type of vegetative development, depending on the atmosphere of incubation. Induction of yeastlike development by CO(2) occurred in five strains of M. rouxii, and in most species of Mucor tested. M. subtilissimus, however, did not require CO(2); it developed in the yeastlike form under anaerobic conditions. Strains of Rhizopus grew under CO(2), but developed only filamentous mycelium. Members of other genera of Mucorales were unable to grow under an atmosphere of CO(2).

Carbon Dioxide↗
PubMed1989

Accumulation of acyclic polyols and trehalose as related to growth form and carbohydrate source in the dimorphic fungi Mucor rouxii and Candida albicans.

Yeast (Y) and hyphal (H) cells of Mucor rouxii and Candida albicans were cultivated in liquid media containing different carbon nutrient sources (glucose, fructose, ribose) and their free acyclic polyol and trehalose contents determined using capillary gas liquid chromatography (TMS- and OAc-derivatization). Irrespective of growth form and C-source, the fraction of the water-soluble neutral components of the cellular mass of the cultures - highly homogeneous with regard to the respective cell form produced - contained glycerol, ribitol and arabitol, in addition to trehalose. The polyols contributed 0.5-2% to the biomass of M. rouxii and 1.5-6% to that of C. albicans; the values for trehalose ranged from 0.2-11% in the former and 1-3.5% in the latter species. Mucor contained higher amounts of ribitol and arabitol in H cells and larger quantities of trehalose and glycerol in Y cells. In Candida, too, hyphae always exhibited higher ribitol contents, whereas arabitol attained higher levels in yeasts under almost any conditions - regardless of the type of medium (synthetic vs. complex), stage of culture (early vs. late log-phase) and strain used. Glycerol concentration was not correlated with the growth form; trehalose contents tended to be higher in Y cells. Taking into account the facts that C. albicans and certain Mucor species are agents of opportunistic infections and are invasive mainly in the filamentous form, and that the prospective hosts do not accumulate either of these carbohydrates, the possibility is considered of using trehalose- and polyol-metabolizing enzymes as targets for designing antifungal drugs.

Candida albicans↗
PubMed1989

Characterization of a leuA gene and an ARS element from Mucor circinelloides.

A 4.4-kb PstI restriction endonuclease fragment of Mucor circinelloides DNA has previously been shown to both complement a leuA- mutation, and to enable the autonomous replication of plasmids within this organism. The complete nucleotide (nt) sequence of this fragment has been determined and an open reading frame of 1935 bp with no introns has been identified, which exhibits significant similarity (75% at the nt level) with 114 bp of the 5' coding region of the Saccharomyces cerevisiae LEU1 gene. Based on this and on the fact that the fragment weakly complements a leu1 auxotroph of S. cerevisiae, we concluded that the Mucor leu gene encodes alpha-isopropylmalate (alpha-IPM) isomerase and designated it leuA+ accordingly. Primer extension analysis of leuA mRNA and Northern-blot hybridization, indicated the leuA transcript to be approx. 2.3 kb in size, with 5'- and 3'-untranslated regions of 16-20 nt and approx. 450 nt, respectively. Specific Mucor ARS sequence(s) were not identified, although the general location of ARS was indicated by subcloning experiments. Nucleotide sequences are present within this region, which show some similarity with the core consensus of the S. cerevisiae ARS; however, any functional homology is doubtful, since insertion of the 4.4-kb PstI fragment into YIp5 did not increase the transformation frequency of S. cerevisiae with such a vector.

Amino Acid Sequence↗
PubMed2005

[Detection of extracellular protease in Mucor species].

The fungi are characterized by their abilities to produce and secrete enzymes to the external environment. The species of genus Mucor are a group of fungal microbes with important biotechnological potential, which are responsible for production of industrial enzymes. This work evaluated the ability of protease production in twelve species of genus Mucor. The strains were kept for 120 h under the incubation temperature of 28 degrees C on a shaker at 120 rpm. The detection of proteolytic activity was evaluated in all species, the higher activity was detected in Mucor racemosus Fres. f. chibinensis (Neophytova) Schipper.

Culture Media↗
PubMedDate not supplied

Production of phytase by Mucor racemosus in solid-state fermentation.

Phytase production was studied by three Mucor and eight Rhizopus strains by solid-state fermentation (SSF) on three commonly used natural feed ingredients (canola meal, coconut oil cake, wheat bran). Mucor racemosus NRRL 1994 (ATCC 46129) gave the highest yield (14.5 IU/g dry matter phytase activity) on coconut oil cake. Optimizing the supplementation of coconut oil cake with glucose, casein and (NH(4))(2)SO(4), phytase production in solid-state fermentation was increased to 26 IU/g dry matter (DM). Optimization was carried out by Plackett-Burman and central composite experimental designs. Using the optimized medium phytase, alpha-amylase and lipase production of Mucor racemosus NRRL 1994 was compared in solid-state fermentation and in shake flask (SF) fermentation. SSF yielded higher phytase activity than did SF based on mass of initial substrate. Because this particular isolate is a food-grade fungus that has been used for sufu fermentation in China, the whole SSF material (crude enzyme, in situ enzyme) may be used directly in animal feed rations with enhanced cost efficiency.

6-Phytase↗
PubMed2006

Gastrointestinal zygomycosis caused by Mucor indicus in a patient with acute traumatic brain injury.

We report a gastrointestinal infection caused by Mucor indicus in a patient with severe head injuries. Monotherapy with high-dose liposomal amphotericin B successfully eradicated the mucormycosis. Nevertheless, subsequently a hemicolectomy was necessary due to recurrent bleeding from a deep ulcer. Mucor indicus is an uncommon fungal pathogen, typically found in starters used for food fermentation. Reviewing other reports on Mucor indicus infections, primary gastrointestinal manifestations seem to be typical and indicate an oral route of infection.

Antifungal Agents↗
PubMed1982

Photo-oxidation of a histidyl residue of milk-clotting acid protease, Mucor rennin.

Mucor rennin, a milk-clotting acid protease produced by a fungus Mucor pusillus, was inactivated by photo-oxidation mediated by methylene blue according to first order kinetics. The pH profile of the inactivation rate showed that a dissociating group with a pK value of 7.6 was involved in the inactivation. Addition of pepstatin A, an inhibitor specific for acid proteases, caused a marked alkaline shift of the pK value. One of two histidyl residues in the enzyme was destroyed by the photo-oxidation, with complete loss of the enzyme activity. Analysis of inhibitor binding activity and chemical modification with diazoacetyl-DL-norleucine suggested that the photo-oxidized enzyme still retained its original conformation. These results indicated that one histidyl residue in addition to the two essential carboxyl groups is involved in the catalytic function of Mucor rennin.

Chymosin↗
PubMed1977

The hyphal wall of Mucor mucedo. 1. Polyanionic polymers.

Treatment of isolated hyphal walls of Mucor mucedo with nitrous acid resulted in the release of two water-soluble polyanions: (a) a glycuronan, containing all the neutral sugars and uronic acid present in the hyphal wall and (b) an inorganic polyphosphate. The glycuronan could also be extracted quantitatively with salt solutions of high ionic strength and partially with a solution of potassium hydroxide. This is presented as evidence that the glycuronan is a genuine constituent of the cell wall, non-covalently bound to glucosamine-containing polymers which are susceptible to depolymerization by nitrous acid. By treatment with acid the glycuronan was partly converted to crystalline poly(glucuronic acid) with the properties of mucoric acid. This strongly suggests that mucoric acid, which can be extracted from the walls of M. mucedo by alkali after acid treatment, is not a genuine wall component but arises by partial acid hydrolysis of the heteropolymeric glycuronan.

Amino Acids↗
PubMed1981

Changes in the rate of chitin-plus-chitosan synthesis accompany morphogenesis of Mucor racemosus.

The in vivo differential rates of chitin-plus-chitosan biosynthesis in Mucor racemosus were determined under a variety of conditions, leading to yeast cell or mycelial morphology. Chitin-chitosan was determined as hot NaOH-insoluble radioactivity derived from N-acetyl-D-[1-3H]glucosamine in the medium. Control experiments demonstrated that the labeled material possessed the properties of chitin-plus-chitosan. Our results indicate that Mucor yeasts have a relatively low differential rate of chitin-plus-chitosan synthesis and that mycelial cells have a threefold-elevated differential rate. Treatment of aerobic cells with exogenous N6, O2-dibutyryl cyclic adenosine 3',5'-monophosphate, an agent which induces yeast cell morphology, also results in a lowered rate of chitin-plus-chitosan synthesis. Control experiments eliminated the possibility that the observed rate changes were due to changes in endogenous pool size, uptake of exogenous N-acetyl-p-[1-3H]glucosamine, or alterations in growth rate. Therefore, the changes are seemingly linked to morphogenesis. These results strengthen the idea that cyclic adenosine 3',5'-monophosphate plays an important role in dimorphism in Mucor. In addition, pulse-chase experiments suggest that considerable modification of newly synthesized chitin plus chitosan in both yeast cells and mycelia occurs in vivo.

Aerobiosis↗
PubMed1969

Stimulation of fermentation and yeast-like morphogenesis in Mucor rouxii by phenethyl alcohol.

The germination of fungal spores into hyphae was inhibited by concentrations of phenethyl alcohol (PEA) from 0.05 to 0.3%. Spores of Mucor formed budding spherical cells instead of filaments. These cells were abundant in cultures of Mucor rouxii at 0.22% PEA, provided that the carbon source was a hexose at 2 to 5%. Morphology was filamentous with xylose, maltose, sucrose, or a mixture of amino acids. Removal of PEA resulted in the conversion of yeast-like cells into hyphae. PEA did not inhibit biosynthesis of cytochromes or oxygen uptake, but it stimulated CO(2) and ethyl alcohol production. PEA had no effect on the rate of oxygen uptake, but it inhibited the oxidative-phosphorylation activity of mitochondria. These results suggested that growth inhibition by PEA could result from uncoupling of oxidative phosphorylation and that, in Mucor, yeast-like morphology and fermentation were linked.

Alcohols↗
PubMed1976

Acid proteases from species of Mucor. III. Interaction with concanavalin A and concanavalin A Sepharose.

The reaction of Mucor miehei protease with concanavalin A was followed by a turbidimetric assay in the pH range 5-8. At pH 4.0, no turbidity developed but binding of the enzyme to concanavalin A could be demonstrated by gel filtration. Two fractions of apparent molecular weight 65000 and 52000 were isolated, the 65000 molecular weight species apparently representing a protomer of concanavalin A (24000) bound to the enzyme. An analysis of the circular dichroism spectrum of this complex suggested that protomer binding results in a conformational change in the enzyme which is associated with a 30% increase in proteolytic activity. At pH 6.0, the enzyme was strongly bound to columns of concanavalin A Sepharose but could be removed by including alpha-methyl D-glucoside and NaC1 in the elution buffer. Some column degradation occurred at room temperature but was not detectable at 4 degrees C where rapid elution of the enzyme resulted in a greater than 90% yield of highly active protein. Periodate-oxidized Mucor miehei protease and Mucor renin did not react with concanavalin A and were not bound to the affinity column.

Binding Sites↗
PubMed1993

Mucor amphibiorum infection in platypus (Ornithorhynchus anatinus) from Tasmania.

Mucor amphibiorum, a fungus previously isolated from frogs and toads, is reported from free-living platypus, Ornithorhynchus anatinus, from rivers in northern Tasmania. This fungus is responsible for the severe ulcerative skin condition originally described by Munday and Peel (1983). Mucor amphibiorum was isolated from dermal lesions on four separate occasions. The gross and histopathological appearance of the fungal lesions were similar to the earlier description. In vivo this fungus develops as spherical forms containing a number of daughter spherules; no mycelia are seen in tissue sections. By contrast, the in vitro growth consists of aerial aseptate mycelia and sporangia, features typical of the genus Mucor. This is the first report of this organism causing a fatal disease in a mammal. Susceptibility to infection may be due to the platypus having a body temperature of 32 C while the maximum temperature for growth of M. amphibiorum is 36 C.

Animals↗