Artificial shiro formation of Tricholoma matsutake

One type of soil collected from Maoer-shan in Heilongjiang Province,China was selected to induce hyphal growth of Tricholoma matsutake by a soil screening experiment.It was confirmed that hyphal growth of all the tested T.matsutake isolates was significantly stimulated in soil by supplemented with 0.5%～2.0% olive oil.The aggregation of hyphae and soil resembled natural Shiro.The biomass of hyphae in the soil increases with increasing olive oil concentrations.Moreover,seedlings of Pinus densiflora grew well in the soil containing 0.5%～1.0% olive oil and were also successfully infected by T.matsutake isolate A in the soil containing 1.0% olive oil.This study established a culture system of artificial Shiro formation and also provided a premise for formulation of culture substratum for fruit body formation of T.matsutake.     

松口蘑人工菌塘诱导形成的初步研究

本研究通过土壤筛选找到适合松口蘑菌丝体生长的土壤,并在其土壤中添加适当浓度的橄榄油(0.5%-2.0%),有效地促进了菌丝体在土壤中的生长,菌丝生长状况酷似野外的松口蘑菌塘,且随着添加浓度的增加,菌丝体生物量呈明显的正相关。当土壤中橄榄油浓度为0.5%和1.0%时,松口蘑共生植物赤松苗的生长不但没有受到抑制,而且还能与菌丝体在这种“菌塘”中形成菌根。本研究成功地建立了中国松口蘑人工菌塘诱导体系,同时也为其人工子实体的诱导研究提供了必要的前提条件。     

Large contribution of arbuscular mycorrhizal fungi to soil carbon pools in tropical forest soils

The origins and composition of soil organic matter (SOM) are still largely uncertain. Arbuscular mycorrhizal fungi (AMF) are recognized as indirect contributors through their influence on soil aggregation, plant physiology, and plant community composition. Here we present evidence that AMF can also make large, direct contributions to SOM. Glomalin, a recently discovered glycoprotein produced by AMF hyphae, was detected in tropical soils in concentrations of over 60 mg cm^–3. Along a chronosequence of soils spanning ages from 300 to 4.1 Mio years, a pattern of glomalin concentrations is consistent with the hypothesis that this protein accumulates in soil. Carbon dating of glomalin indicated turnover at time scales of several years to decades, much longer than the turnover of AMF hyphae (which is assumed to be on the order of days to weeks). This suggests that contributions of mycorrhizae to soil carbon storage based on hyphal biomass in soil and roots may be an underestimate. The amount of C and N in glomalin represented a sizeable amount (ca. 4–5%) of total soil C and N in the oldest soils. Our results thus indicate that microbial (fungal) carbon that is not derived from above- or below-ground litter can make a significant contribution to soil carbon and nitrogen pools and can far exceed the contributions of soil microbial biomass (ranging from 0.08 to 0.2% of total C for the oldest soils).     

The effect of soil phosphorus on the external mycelium growth of arbuscular mycorrhizal fungi during the early stages of mycorrhiza formation

The effects of soil P amendments and time of application on the formation of external mycelium by different arbuscular mycorrhizal (AM) fungi were studied. In the first experiment the external mycelium produced in the soil by the AM fungus Glomus etunicatum Beck. and Gerd., during the early stages of root colonization (7 and 14 days after inoculation), was quantified by the soil-agar film technique. A Brazilian Oxisol was used with three different phosphate levels, varying from deficient to supra-optimal for the plant. Significant differences were observed in the phosphate and inoculation treatments for plant dry weight, P content in the tissue, root length and root colonization, at fourteen days after planting. At 7 days, mycelium growth, root colonization and their relationship were reduced at supra-optimal P concentrations. Applications of P one week after planting reduced mycelium growth and root colonization more than when applied to the soil before planting. In a second experiment the arbuscular mycorrhizal (AM) fungi, Scutellospora heterogama (Nicol. and Gerd.) Walker and Sanders and E3 were tested and compared with Glomus etunicatum. For the species studied, the length of external hyphae per unit of colonized root length was affected by small P additions but no further significant differences were observed at high P levels. The three AM endophytes showed marked differences in their response to P in the soil: Scutellospora heterogama, although producing external mycelium more profusely than the Glomus spp., showed a higher sensitivity to soil P supply.     

Reaction of forest soil microflora to environmental stress along a moderate pollution gradient next to an oil refinery

Twenty-five study sites were established along a 57-km-long transect in order to estimate the impact of an oil refinery, mainly emitting sulphur dioxide (24000 t yr⁻¹), on forest soil (F/H-horizon) chemistry and microbiology. The study demonstrated the existence of a pollution gradient which was best represented by the logarithm of the concentration of vanadium in the analyzed F/H soil layer. Of the soil microbial characteristics measured, including length of fungal hyphae, soil respiration, microbial biomass C and N, and percentage mass loss of Scots pine (Pinus sylvestris) needle litter, only fungal hyphal length was suppressed by the pollution load. No reduction in basic cations (Ca, Mg, K, and Na) in the F/H-horizon, or enrichment of soluble aluminum in the F/H-horizon of the Scots pine forest could be detected to result from the deposition.     

Kinetics of lipase-catalyzed hydrolysis of olive oil in AOT/isooctane reversed micelles

The kinetics of lipase-catalyzed hydrolysis of olive oil in AOT/isooctane reversed micellar media was studied. It was shown that the deactivation of lipase had a great influence on the reaction kinetics. Based on whether the enzyme deactivation and influences of both product and substrate on enzyme stability were included or not, four different kinetic models were established. The simulating results demonstrated that the kinetic model, which including product inhibition, enzyme deactivation and the improvements of lipase stability by both product and substrate, fit the experimental data best with an overall relative error of 4.68%.     

Mechanics of Solid Tissue Invasion by the Mammalian Pathogen Pythium insidiosum

The relative significance of mechanical penetration versus the action of substrate-degrading enzymes during solid tissue invasion has not been established for any fungal disease. Pythium insidiosum is an oomycete fungus (or stramenopile) that causes a rare, but potentially lethal infection in humans and other mammalian hosts. Experiments with miniature strain gauges showed that single hyphal apices of this pathogen exert forces of up to 6.9 μN, corresponding to maximum pressures of 0.3 μN μm⁻² or MPa. Samples of cutaneous and subcutaneous tissue from fresh human cadavers displayed a mean strength (resistance to needle puncture) of 24 μN μm⁻², and a mean pressure of 30 μN μm⁻² was necessary to penetrate skin strips from slaughtered horses. These experiments demonstrate that P. insidiosum does not exert sufficient pressure to penetrate undamaged skin by mechanics alone, but must effect a decisive reduction in tissue strength by proteinase secretion.     

Essential oil composition of two endemic Centaurea species from Turkey, Centaurea mucronifera and Centaurea chrysantha, collected in the same habitat

The essential oils of two endemic Centaurea species from Turkey, C. mucronifera and C. chrysantha, collected in the same habitat, have been studied. The main compounds of the former were germacrene D (29.3%), β-eudesmol (17.4%) and β-caryophyllene (7.3%), while in the latter germacrene D (27.4%), caryophyllene oxide (9.5%) and bicyclogermacrene (5.4%) were detected among its major constituents. The two species produced many similar compounds in their essential oils that could be justified by the similar ecological conditions of their habitat, but also many differences were found that could confirm their taxonomic separation.     

Ultrasonication enhanced hydrolytic activity of lipase in water/isooctane two-phase systems

The hydrolysis of olive oil catalyzed by Chromobacterium viscosum lipase (EC 3.1.1.3) in a water/isooctane two-phase system was carried out both under ultrasound and conventional stirring. The maximum activity of lipase in the ultrasonicated system was 1.75 times higher than that in the stirred system. The lipase activity was dependent on ultrasonic power and volume ratio of isooctane to water. The optimum reaction temperature in both systems was around 25°C. The stability of lipase at 25°C in the ultrasonicated system decreased more rapidly than that in the stirred system. In the presence of exogenous oleic acid, however the half-life of lipase in the ultrasonicated system was improved to a value, which was respectively half and twice of that in stirred systems with and without oleic acid. The maximum reaction rate (V_max) was increased by ultrasonication whereas the Michaelis constant (K_m) remained unaltered.     

Septum formation in Aspergillus nidulans

Filamentous fungi form multicellular hyphae that are partitioned by septa. In A. nidulans, septum formation requires the assembly of a septal band following the completion of mitosis. Recent observations show that this band is a dynamic structure composed of actin, a septin and a formin. In addition, assembly is dependent upon a conserved protein kinase cascade that regulates mitotic exit and septation in yeast. Hyphal differentiation may reflect the regulation of this cascade by cyclin-dependent kinase activity. In this review, the dynamics and regulation underlying the assembly of the septal band are discussed.     

Lipase-catalyzed hydrolysis of olive oil in chemically-modified AOT/isooctane reverse micelles in a hollow fiber membrane reactor

The hydrolysis of olive oil catalyzed by Candida rugosa lipase in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane and the synthetic sodium bis(2-ethylhexyl polyoxyethylene)sulfosuccinate (MAOT)/isooctane reverse micellar systems was investigated in a polysulfone hollow fiber membrane reactor with recycle of the reaction mixture. Lipase was completely retained by the membrane while olive oil and oleic acid freely passed through. The retention of reverse micelles depended on W ₀ (molar ratio of water to surfactant). At an olive oil concentration of 0.23 mol l^–1 the final substrate conversion in the MAOT micellar system was about 1.4 times of that in the AOT micellar system.     

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.     

Valorisation of wastepaper using the fibrolytic/hydrogen producing bacterium Ruminococcus albus

The present study aimed to investigate the biotransformation of different kinds of wastepaper to hydrogen by the fibrotylic bacterium Ruminococcus albus. Five different types i.e. paper tissue, office paper, illustrated magazine paper, paperboard and newspaper, were selected as representatives of the most common types of wastepaper found in municipal solid wastes. The percentage of total carbohydrates measured as glucose equivalents, ranged from 50% to 100% (w/w), whereas the bioconversion by R. albus ranged from 18% to 100% of their initial weigh. The only metabolic products detected in all cases were acetate, ethanol, formate, hydrogen and carbon dioxide. The hydrogen yields ranged from 46 to 280 L H₂/kg paper, indicating that wastepaper could be a promising candidate for second generation biohydrogen production. Subsequently, hydrolysis was investigated for paper tissue and paperboard. It was shown that in both cases the degradation process could be satisfactory described by zero order kinetics and it was identified to be the rate limiting step for the whole process, controlling biomass growth and metabolites generation rate.     

Initiation of aerial mycelium formation in Streptomyces

In the past two years, the isolation of extracellular factors involved in the initiation of aerial mycelium formation, the identification of metabolic defects in certain developmental mutants, and the characterisation of three further bld genes and several γ-butyrolactone receptor genes have led to new ideas about the mechanisms that initiate aerial mycelium formation in Streptomyces. The emerging picture suggests the integration of numerous signals from both inside and outside the cell.     

Biocatalysed synthesis of sn-1,3-diacylglycerol oil from extra virgin olive oil

Enzymatic synthesis of sn-1,3-diacylglycerols (sn-1,3-DAG) in two steps without isolation of the intermediates was investigated. Firstly ethanolysis of extra virgin olive oil (EVO) using immobilized non-regiospecific lipase from Candida antarctica (Novozym 435) was carried out to obtain glycerol (Gly) and fatty acid ethyl esters (FAEE). In the second step the ethanolysis products have been re-esterificated testing different sn-1,3-regiospecific lipases, both immobilized and non-immobilized, in different reaction media, that is in the presence of solvents or in a solvent-free system, for different times, at different temperatures (12, 25 and 40 °C). The lipase from Rhizomucor miehei (Lipozyme IM) has been the most effective among the sn-1,3-specific lipases screened.