J. Antonio Leal

Heterogeneity of the genus Myrothecium as revealed by cell wall polysaccharides

Abstract.The polysaccharides obtained from the alkali-extractable, water-soluble fraction (F1SS) from the cell wall of Myrothecium verrucaria and Myrothecium atroviride were shown to be composed of β-(1→6)-galactofuranose fully substituted at O-2 by terminal residues of α-glucopyranose and α-glucuronic acid. Glucuronic acid was substituted at O-4 by glucopyranose in the Myrothecium species M. inundatum, M. setiramosum, M. prestonii, M. tongaense and M. roridum. The acidic polysaccharides from Phaeostilbella atra (=Myrothecium atrum) and Myrothecium gramineum lacked the backbone of 2,6 di-O-substituted galactofuranose and contained a high amount of O-5-substituted β-galactofuranose. The structures of the polysaccharides isolated from Myrothecium cinctum and Myrothecium penicilloides were unrelated to each other and to the polysaccharides from the other species analysed. The usefulness of these polysaccharides as a characteristic for delimitation of the genus Myrothecium is discussed.

A polysaccharide from Lichina pygmaea and L. confinis supports the recognition of Lichinomycetes

The lichen-forming order Lichinales, generally characterized by prototunicate asci and the development of thalli with cyanobacteria, has recently been recognized as a separate class of ascomycetes, Lichinomycetes, as a result of molecular phylogenetic studies. As alkali and water-soluble (F1SS) polysaccharides reflect phylogeny in other ascomycetes, a polysaccharide from Lichina pygmaea and L. confinis was purified and characterized to investigate whether these F1SS compounds in the Lichinomycetes were distinctive. Nuclear magnetic resonance (NMR) spectroscopy and chemical analyses revealed this as a galactomannan comprising a repeating unit consisting of an alpha-(1-->6)-mannan backbone, mainly substituted by single alpha-galactofuranose residues at the O-2- or the O-2,4- positions linked to a small mannan core. With the exception of the trisubstituted mannopyranose residues previously described in polysaccharides from other lichens belonging to orders now placed in Lecanoromycetes, the structure of this galactomannan most closely resembles those found in several members of the Onygenales in Eurotiomycetes. Our polysaccharide data support molecular studies showing that Lichina species are remote from Lecanoromycetes as the galactofuranose residues are in the alpha-configuration. That the Lichinomycetes were part of an ancestral lichenized group can not be established from the present data because the extracted polysaccharide does not have the galactofuranose residue in the beta configuration; however, the data does suggest that an ancestor of the Lichinomycetes contained a mannan and was part of an early radiation in the ascomycetes.

The effect of light and darkness on the germination of the oospores of certain species of Phytophthora on some synthetic media

The germination of oospores of Phytophthora heveae Thompson, by the production of zoosporangia, on different media, is shown to follow from a period of maturation in the dark followed by exposure to daylight. Germination was also dependent on the nitrogen and carbon source. Similar behaviour is reported for P. cactorum (Leb. & Cohn) Schroet. and for P. erythroseptica Pethybr. except that the latter produces a germ tube only.

Comparison of cell-wall polysaccharides from Nectria cinnabarina with those from the group of Nectria with Sesquicillium anamorphs.

Alkali-extractable and water-soluble polysaccharides were purified from cell walls of five species of Sesquicillium or its teleomorphs, Nectria lasiacidis and Nectria impariphialis, and from Nectria cinnabarina, the type species of Nectria, a heterogeneous genus that belongs to the Hypocreales. Methylation and NMR analyses for determination of linkage types and structure were performed and indicated differences between the polysaccharides purified during the present study and those isolated from other nectrioid fungi, namely the presence of 5-O-substituted galactofuranose (-->5)-Galf-(1-->) in the main chain together with 2,6-di-O-substituted galactofuranose (-->2,6)-Galf-(1-->) residues in Sesquicillium buxi and Sesquicillium pseudosetosum. The polysaccharide from N. impariphialis was similar to those obtained from the above species, although an additional residue of 6-O-substituted glucopyranose (-->6)-Glcp-(1-->), was detected in some side chains. In N. lasiacidis and Sesquicillium candelabrum the polysaccharide contained an additional branching point of 5,6-di-O-substituted galactofuranose (-->5,6)-Galf-(1-->) linked to terminal N-acetylglucosamine GlcNAc-(1-->). These chains were linked to a small mannan core. All these polysaccharides showed major differences to the polysaccharide of N. cinnabarina, which was formed by a main chain of (1-->6)-beta-linked galactofuranose units almost fully branched at positions 2-O by either single residues of glucopyranose or acidic chains containing glucuronic acid and mannose.

Effect of culture age on cell wall polysaccharides ofPenicillium allahabadense

Abstract Cell walls were obtained from Penicillium allahabadense mycelia of different ages. The yield of walls increased with the age of the culture, but the increase was very slow after the 20th day. Cell walls from 5-day-old mycelia consisted of neutral sugars (54%), chitin (25%), and protein (4%). The neutral sugars identified and quantified by gas-liquid chromatography were mannose (6.5%), galactose (19%), and glucose (24%). Slight changes were found in the content of galactose and glucose in the walls derived from mycelium of cultures up to 20 days of age. The content of these sugars decreased afterward. In the same period of time, the content of mannose increased about twofold and remained almost constant in the following days. The content of chitin first slightly decreased, and then increased with the age of the cultures. The fractions solubilized by alkali from the cell walls were composed mainly of galactose, glucose, and mannose. Most of the galactose in the cell walls or wall fractions was released by hydrolysis with 0.2 N H 2 SO 4 , characteristic of galactofuranosyl residues.

The chemical composition of the wall of six species of Aphanoascus: the taxonomic significance of the presence of α-(1-2) (1-6) mannan and α-(1-4) glucan

The main polysaccharide fractions extracted with 1 m -NaOH from cell wall material of different species of Aphanoascus were characterized as a glucomannan (F1S) which amounted to 4·0–10·5% and a glucan-chitin complex (F4I) representing from 56 to 69%. The neutral sugar content of fraction F1S in A. fulvescens, A. mephitalus, A. reticulisporus and A. saturnoideus was mannose (54–70·6%), galactose (0·5–7·8%) and glucose (4·0–9·1%). In A. terreus and A. verrucosus the content of glucose was 34·6 and 21·7% and mannose 54·0 and 17·0% respectively. Fraction F1S consumed 0·95 to 1·35 mol of periodate per hexose residue. The main products detected after complete Smith degradation were glycerol and erythritol. Fraction F4I contained glucose (58–64%) and glucosamine (30–35%) except in A. fulvescens (12–13%). From fraction F1S of A. fulvescens an α-(1–4)-glucan (20·5%) and a were obtained. These two polysaccharides are good chemotaxonomic characters for the definition of the genus Aphanoascus .

Mannoglucogalactans from the cell walls of Penicillium erythromellis: Isolation and partial characterisation☆

Abstract Cell-wall material from Penicillium erythromellis was extracted with m sodium hydroxie at 20°. After neutralisation and dialysis of the alkali-soluble material, two polysaccharidic fractions were isolated, namely, a β-glucan (glucose, 49%) containing galactose (6.9%), xylose (3.7%), mannose (1.9%), and protein (9%), and a glucogalactan (glucose, 15%) with galactofuranosyl residues (39%), containing mannose (5.3%) and protein (18%). Borate anion-exchange chromatography of the glucogalactan gave five polysaccharides, the relative amounts of which, in order of elution, were 1.5:1.0:2.4:7.1:2.1. When the three polysaccharides with the highest carbohydrate content were subjected to methylation analysis, one was shown to be a (1→4)-α- d -glucan with branch points at positions 6 (12.2%), and glucopyranose (5.8%) and galactofuranose (3.4%) as terminal residues, and the others to be β-glucogalactans with diffrent proportions of galactofuranose and glucopyranose residues. The galactofuranosyl residues were (1→2)-linked with branch points at positions 6, and galactofuranose as terminal residues. The glucopyranosyl residues were mainly (1→4)-linked with glucopyranose as terminal residues.

Cell wall polysaccharides of four strains ofPaecilomyces variotii

The main polysaccharidic fractions extracted with 1m NaOH from cell wall material of four different strains ofPaecilomyces variotii were characterized as an α-(1→3)-glucan (F1I) amounting from 33.2 to 39.1% and a β-glucan-chitin complex (F4) representing from 42.7 to 47.3%. The water-soluble fraction, F1S, was composed of mannose, glucose, and mainly galactose in all the strains studied. The F1S fractions of the four strains were analyzed by NMR spectroscopy showing analogous structural features in all the strains. This fraction was purified through Sepharose CL-6B and methylated. The purified material (F1S-B) mainly contained (1→6)- and (1→2,6)-linked mannopyranose, (1→5)- and (1→6)-linked galactofuranose, and terminal residues of glucopyranose and galactofuranose. The proportion, the chemical composition, and the structure of each fraction revealed a homogeneous cell wall composition in these strains.

Alkali-extractable and water-soluble polysaccharide (F1SS): a chemotaxonomic and phylogenetic character for Cephalotheca

The cell wall alkali-extractable water-soluble polysaccharide (F1SS) purified from the three species of Cephalotheca has been characterized. Two different structures have been deduced by chemical and structural analyses. The structure of the polysaccharide F1SS from C. purpurea and C. reniformis is similar, and composed of 3,6-di-O-substituted mannopyranose with terminal residues of rhamnopyranose. The polysaccharide F1SS from C. sulfurea contains 2,6-di-O-substituted mannopyranose and terminal residues of galactofuranose. Our results confirm the relatedness of C. purpurea and C. reniformis with Ophiostomatales and of C. sulfurea with Sordariales.

Polysaccharides from Hemileia vastatrix uredospores

Abstract The polysaccharidic fractions isolated from Hemileia vastatrix uredospores by alkali treatment, expressed as a percentage of the initial uredospore weight, gave the following yields: 1 M NaOH soluble at 22°C (7.1); 1 M NaOH soluble at 60°C (5.0); and insoluble residue (7.6). Both alkali-soluble fractions contained mannose and glucose as the major constituents, with glycosidic linkages of the β-1 → 4 and β-1 → 3 types. The alkaliinsoluble residue contained predominantly glucosamine, and had infrared and X-ray spectra indistingushable from those of crustacean chitin. Electron microscope observations revealed that the insoluble residue consisted of the cell wall spines connected by a thin layer of microfibrils.