Utilization of oligosaccharides by three imperfect fungi

Summary The utilization of oligosaccharides (maltose, sucrose, lactose and raffinose) by three imperfect fungi viz.Alternaria tenuis Auct.,Colletotrichum capsici (Syd.)Butler &Bisby andColletotrichum gloeosporioides Penz. isolated from diseased leaves of tomato,Scindapsus pictus andPolyscias balfuriana respectively, was studied chromatographically. Except for lactose, all the sugars were utilizzed through a hydrolytic pathway and almost all proved to be a suitable source of carbon for the growth of fungi. Along with the utilization of sucrose, a simultaneous synthesis of an oligosaccharide was also observed in case of two species ofColletotrichum. C. gloeosporioides, however, also synthesized an oligosaccharide, maltotriose if it is grown in the medium containing maltose. During the utilization of raffinose, melibiose and fructose were detectted in the culture medium ofA. tenuis. Melibiose was further broken down into glucose and galactose by the two species ofColletotrichum.All the sugars were consumed from the media within 15 days except for lactose which persisted in the media even after 15 days.     

Studies on metabolic inhibitors I. Guanidine hydrochloride and utilization of sucrose by pathogenic Fusaria

Summary The impact of guanidine hydrochloride on the utilization and synthesis of oligosaccharides by pathogenicFusaria from sucrose solution, was studied employing chromatographic technique. The results are significant, in that, they show that the site of action is remote from the enzyme -fructosidase which is not disrupted by this chemical into its component units — the isozymes, and the chemical signal is interpreted by the operon governing the enzyme synthesis. The possibility of the enzyme -fructosidase undergoing an allosteric transition with modification of its active site is also discussed in the light of experimental results.     

Studies on the synthesis of Lewis-y oligosaccharides

Lewis-y histo-blood group oligosaccharides are tumour-associated antigens prevalent in several different types of cancer, and they may also be secondary ligands for bacterial toxins from Escherichia coli and Vibrio cholerae. The key step in the synthesis of these sterically congested oligosaccharides involves difucosylation of partially protected lactosamine derivatives. Existing methods require either prolonged reaction times or elaborate glycosyl donors to ensure high stereoselectivity. Herein we report an optimised procedure for using a simple thioglycoside donor that leads to the desired products in high yield and excellent stereoselectivity. It is found that initial glycosylation of the 3′-hydroxy group of lactosamine derivatives in dichloromethane solution can inhibit subsequent glycosylation at the 2-position; however, reaction in toluene solution leads to Lewis-y oligosaccharides in high yield.     

Studies on the synnematous fungi imperfecti. I

Summary Pseudographiella with the type species,P. variaseptata, andPhragmographium with the type species,P. ulmi, are described as new synnematous taxa. Both of these new species produce phragmospores. In addition, a new species ofDendrostilbella, D. bonari, is described as new.     

Effect of fructose and glucose supplementation on invertase mediated synthesis of oligosaccharides from sucrose

Summary The total amount of novel oligosaccharides synthesized by -D-fructofuranosidase at pH 7.5 increased three-fold using a medium composed of 1.2M sucrose, 0.5M fructose and 0.1M glucose, as compared to that with only 1.8M sucrose solution. Using 0.6M of the three sugars did not increase yield but reduced rate of sucrose hydrolysis by 72.7%. Synthesis of fructosyl/glucosyl oligosaccharides based on -fructofuranosidase mediated transglycosylation is enhanced by supplementation of sucrose solution with appropriate concentrations fructose and glucose.     

Studies on the physiological bases of morphogenesis in fungi; the respiratory metabolism of dimorphic pathogenic fungi

The interconversions of mycelial and yeast-like forms (M right harpoon over left harpoon Y) in Blastomyces dermatitidis and in Blastomyces brasiliensis are characterized as examples of thermal dimorphism since the phenomena are apparently dependent only on the temperature of incubation of these two species. The change in morphology consequent upon Y --> M conversion is considered to result from the selective inhibition of cell division, without the simultaneous inhibition of growth. Such selective inhibition is viewed in a wider context as an example of the differential operation of the physicochemical apparatus of the cell in the control of form development by an organism. To analyze this differential operation, which is here dependent only on temperature, we have studied the effect of temperature on oxygen consumption by each of the dimorphic forms. In the absence of external substrate the yeast forms consume 5 to 6 times more oxygen per unit dry weight than do the M forms.The Y forms exhibit an exogenous oxidation of acetate and of glucose, as well as an oxidative assimilation of these substrates, whereas the M forms exhibit no exogenous metabolism in either a resting or starved condition. A study of the effect of a wide range of temperatures on oxygen consumption by the M forms indicates the operation of two rate-limiting processes: (a) one with an activation energy of 13,250 calories/gm. molecule over the range 5-30 degrees , and (b) reversible enzyme inactivation; the latter process assuming importance in the higher temperature range. On abrupt, large changes in temperature the balance between these two rate-limiting reactions (which it is suggested characterizes the steady state) is apparently disrupted as a result of a lag in the assumption of a rate of reversible enzyme inactivation characteristic of the new temperature. This disruption of balance is evidenced in overshoot phenomena. The effect of an analogous disruption of balance, and of increasing enzymic inactivation; on a competition between enzyme systems, competing for substrate for cell elongation and for cell division, is considered in explanation of the observed dependence of the cell division mechanism on the maintenance of an elevated temperature.     

Simultaneous utilization of glucose and sucrose by thermophilic fungi.

The utilization of mixtures of glucose and sucrose at nonlimiting concentrations was studied in batch cultures of two common thermophilic fungi, Thermomyces lanuginosus and Penicilium duponti. The sucrose-utilizing enzymes (sucrose permease and invertase) in both fungi were inducible. Both sugars were used concurrently, regardless of their relative proportion in the mixture. At the optimal growth temperature (50 degrees C), T. lanuginosus utilized sucrose earlier than it did glucose, but at a suboptimal growth temperature (30 degrees C) the two sugars were utilized at nearly comparable rates. The coutilization of the two sugars was most likely possible because (i) invertase was insensitive to catabolite repression by glucose, (ii) the activity and affinity of the glucose transport system were lowered when sucrose was included in the growth medium, and (iii) the activity of the glucose uptake system was also subject to repression by high concentrations of glucose itself. The concurrent utilization of the available carbon sources by thermophilic fungi might be an adaptive strategy for opportunistic growth in nature under conditions of low nutrient availability and thermal fluctuations in the environment.     

Interaction between pathogenic fungi in culture. Considerations on the mechanism of cell division in the dimorphism of pathogenic fungi

Summary A mutual antagonism (in vitro) has been shown betweenTrichophyton rubrum andCandida albicans by means of two membered pure cultures and by means of cultures filtrates from each organism grown singly. The growth ofT. rubrum was inhibited by metabolic products ofC. albicans. The pigment ofT. rubrum has been shown to be a pH indicator in vivo. Metabolic products ofT. rubrum completely inhibit the development of mycelia byC. albicans, but have little effect on growth in the yeast phase. Chemical fractionation experiments indicated that there are two diffusible metabolic products ofT. rubrum affecting mycelia development: 1) soluble in water and in acetone, heat stable, and adsorbed by activated charcoal, 2) soluble in water, insoluble in acetone, heat labile, and not adsorbed by activated charcoal. The general phenomenon of yeast to mycelia conversions has been considered in detail. A notation system has been developed in this connection; yeast (Y) to mycelia (M) transformations may be expressed as YM; interconversions of the type exhibited byBlastomyces may be written Y:M. The relationships between these processes and the analogous bacteria (B) to filament (F) conversions, B F, has been pointed out. Evidence that Y..M, YM, and BF may result from the inhibition of a common unit enzymatic mechanism has been presented. Converging evidence from such diverse fields as the physicochemical study of the kinetics of bacterial growth (Hinshelwood), genetics of irradiated bacteria (Witkin; Eisenstark andClark), cytochemical mechanism of penicillin action (Pratt andDufrenoy), and dimorphism of pathogenic fungi (this paper;Nickerson andEdwards) are all interpreted as pointing in this direction.     

Specificity of antigens from pathogenic Aspergillus species. I. Studies with ELISA and immunofluorescence

Studies were made by enzyme linked immunosorbent assay (ELISA) and indirect fluorescent antibody (IFA) tests on the reactivities and specificities of 13 antigens prepared from four species of Aspergillus against antisera from immunized rabbits and 64 sera from patients with aspergillosis, other systemic mycoses and nocardiosis. Although reactions in both serological tests were invariably strongest with homologous antigen: antibody systems, antisera from rabbits immunized with A. fumigatus, Blastomyces dermatitidis, Candida albicans and Paracoccidioides brasiliensis reacted in the ELISA test with all of the Aspergillus antigens. In contrast, cross-reactivity was virtually non-existent with antiserum to Histoplasma capsulatum. Of five antigens prepared from A fumigatus tested by ELISA against human sera from patients with aspergillosis and other nocardial and systemic fungal infections, sensitivities varied from 81 to 100% for sera from 32 patients with aspergillosis, and specificities from 20 to 97% for sera from 30 patients with nocardiosis and other systemic mycoses. Purified A. fumigatus C antigen reacted weakly with sera from eight of these 30 patients, but the reactions were readily distinguishable from those obtained with sera from patients with aspergillosis. At optimal serum dilutions, cross-reactivities of A. fumigatus in the IFA studies were non-existent in the sera from 28 patients with candidosis, coccidioidomycosis, cryptococcosis, histoplasmosis, paracoccidioidomycosis and nocardiosis. Sensitivities of IFA were 94% for patients with aspergilloma and 83% for patients with allergic bronchopulmonary aspergillosis.     

The synthesis of complex-type oligosaccharides. I. Structure of the lipid-linked oligosaccharide precursor of the complex-type oligosaccharides of the vesicular stomatitis virus G protein.

The synthesis of the complex-type oligosaccharide unit of the vesicular stomatitis virus G protein is initiated by the en bloc transfer of a high molecular weight oligosaccharide from a lipid carrier to the nascent polypeptide. Following transfer the oligosaccharide is "processed" by removal of glucose and mannose residues and the sugars that constitute the outer branches of the complex-type oligosaccharide are added. The structure of the oligosaccharide moiety of the lipid-linked precursor has been elucidated in order to further define the steps involved in processing. Since it was not feasible to obtain adequate amounts of material for standard structural studies, most of the structural studies were performed on radiolabeled material, with radioactivity incorporated differentially into glucose, mannose, and N-acetylglucosamine. Based on endo-beta-N-acetylglucosaminidase CII digestion, alpha-mannosidase digestion, acetolysis, Smith periodate degradation, methylation analysis, and periodate oxidation, we propose the following structure for the oligosaccharide moiety of the lipid-linked oligosaccharide.     

茶树内生真菌混合培养增强对植物病原真菌的拮抗作用

采用分离自健康茶树叶片组织中的2株内生真菌,长枝木霉CSN-18和曲霉CSN-3,研究了单独培养和混合培养条件下培养原液与培养原液乙酸乙酯萃取液对植物病原真菌的抑制作用。与2菌株单独培养相比,混合培养对稻瘟病菌Magnaporthe grisea、茶花褐斑病菌Phyllosticta camelliaecola和茶云纹叶枯病菌Guignardia camellia等8种植物病原真菌的抑制作用明显增强。混合培养原液的乙酸乙酯萃取液对茶花褐斑病菌、稻瘟病菌和茶云纹叶枯病菌的抑制率分别为79.48%±1.46%、76.99%±0.91%和71.51%±4.93%;对茶花褐斑病菌、茶云纹叶枯病菌和稻瘟病菌孢子萌发的抑制率分别为100.00%、90.90%±2.59%和84.00%±5.29%。混合培养原液对茶花褐斑病菌菌丝生长的抑制作用也比两菌株的单独培养液有明显增强;在低浓度下,混合培养原液对茶花褐斑病菌的孢子萌发有促进作用;但浓度超过40%,则明显抑制茶花褐斑病菌孢子的萌发。