Basidiochrome -- a novel siderophore of the Orchidaceous Mycorrhizal Fungi Ceratobasidium and Rhizoctonia spp.

A novel trishydroxamate siderophore, named basidiochrome, was isolated as the principal siderophore from low-iron culture filtrates of Ceratobasidium and Rhizoctonia species which are known as mycorrhizal fungi associated with orchid roots. Ion-exchange chromatography and preparative HPLC yielded a pure compound which contained two components according to GC-MS analysis: L: -N(5)-hydroxy-ornithine and 3-methyl-2-cis-pentenedioic acid (3-methyl-cis-glutaconic acid). FTICR-ESI-MS of both the iron-free and ferric form indicated an elemental composition of C(33)H(47)N(6)O(16)Fe (MW = 839) for the ferric form of basidiochrome. The connectivity was further elucidated by 2D-NMR techniques (HSQC, HMBC, COSY, NOESY) indicating that basidiochrome is a novel linear tripeptide consisting of three L: -N(5)-hydroxy-ornithines each linked to 3-methyl-2-cis-pentenedioic acid residues.

Red list plants: colonization by arbuscular mycorrhizal fungi and dark septate endophytes.

Since information concerning the mycorrhization of endangered plants is of major importance for their potential re-establishment, we determined the mycorrhizal status of Serratula tinctoria (Asteraceae), Betonica officinalis (Lamiaceae), Drosera intermedia (Droseraceae) and Lycopodiella inundata (Lycopodiaceae), occurring at one of two wetland sites (fen meadow and peat bog), which differed in soil pH and available P levels. Root colonization by arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) was quantified. Colonization by AMF appeared to be more frequent in the fen meadow than in the peat bog, and depended on the host plant. Roots of S. tinctoria and B. officinalis were well colonized by AMF in the fen meadow (35-55% root length) and both arbuscules and vesicles were observed to occur in spring as well as in autumn. In the peat bog, L. inundata showed a low level of root colonization in spring, when vesicles were found frequently but no arbuscules. In roots of D. intermedia from the peat bog, arbuscules and vesicles were observed, but AMF colonization was lower than in L. inundata. In contrast, the amount of AMF spores extracted from soil at the peat bog site was higher than from the fen meadow soil. Spore numbers did not differ between spring and autumn in the fen meadow, but they were higher in spring than in autumn in the peat bog. Acaulospora laevis or A. colossica and Glomus etunicatum were identified amongst the AMF spores extracted from soil at the two sites. S. tinctoria and B. officinalis roots were also regularly colonized by DSE (18-40% root length), while L. inundata was only rarely colonized and D. intermedia did not seem to be colonized by DSE at all.

Ferricrocin--an ectomycorrhizal siderophore of Cenococcum geophilum.

The ectomycorrhizal fungus Cenococcum geophilum was grown in low-iron medium and the excreted siderophores were extracted, purified and analyzed by HPLC. The principal hydroxamate siderophore produced, was identified as ferricrocin as confirmed by analytical HPLC, FAB-mass spectrometry and 1H- and 13C-NMR spectra. Although the occurrence of ferricrocin has been shown earlier to occur in the ericoid mycorrhizal fungi, this is the first report of ferricrocin in a true ectomycorrhizal fungus which is taxonomically related to the ascomycetes.

Hydroxamate siderophore synthesis by Phialocephala fortinii, a typical dark septate fungal root endophyte.

The siderophore production of various isolates of Phialocephala fortinii was assessed quantitatively as well as qualitatively in batch assays under pure culture conditions at different pH values and iron(III) concentrations. We found a distinct effect of both of these parameters on siderophore synthesis and as well as on fungal growth. In comparative analyses of two of the isolates, maximum siderophore production was found at a pH in the range of pH 4.0 to 4.5 while, under the experimental conditions employed, the optimal concentration of ferric iron was determined to be between 20-40 microg iron (III) l(-1) (0.36-0.72 microM, respectively). HPLC analysis of the culture filtrate of most of the isolates of P. fortinii revealed the excretion of ferricrocin as main hydroxamate siderophore, followed by ferrirubin and ferrichrome C. The pattern of release of these three substances proved to be dependent on pH and iron(III) concentration of the culture medium, and to be specific for each isolate under investigation.

Further evidence in support of the authenticity of microorganisms believed to have survived for 5300 years.

It has been questioned whether the microorganisms isolated from hay, which the ice-man had used for padding his boots, were authentic. The arguments in favour of, and those brought forward against, the authenticity are discussed. Based upon additional circumstantial evidence we maintain our view that the microbial strains isolated from the grass samples are more likely to be of ancient origin than to have been derived from secondary contamination.

Microorganisms surviving for 5300 years.

Recently, the well-preserved corpse of a prehistoric man with an age of approximately 5300 years bp was discovered in the Central European Alps. Analysis of materials associated with the individual has revealed the presence of microorganisms which are believed to have survived since the time of death. So far, two fungi have been isolated and identified as species of the genera Chaetomium and Absidia, respectively. In addition, we have obtained one bacterial isolate which we have identified as a Streptomyces species. Our findings demonstrate that microorganisms can remain viable under appropriate circumstances for thousands of years. The isolates may enable us to study evolutionary trends within microorganisms.

Reversibility of oxygen switch-off effect on Bacillus polymyxa nitrogenase.

The objective of this study was to analyse in vivo the effect of oxygen on the nitrogenase of Bacillus polymyxa. The culture technique employed in this study prevented spore formation by B. polymyxa during the entire period of exposure to acetylene. Under these conditions the acetylene-reduction assay allowed quantification of nitrogenase activity over long incubation periods (44 h). Nitrogenase activity was highest in cells harvested in the late logarithmic phase. At PO2 of 0.19 and 0.37 kPa, acetylene reduction was inhibited by 80 and 100%, respectively. This switch-off effect could be reversed through oxygen exhaustion, either by flushing the culture with N2 or by cellular respiration, suggesting a respiratory protection mechanism for the nitrogenase complex in B. polymyxa. Oxygen consumption measured by a closed-chamber respirometer showed a linear increase up to a PO2 of 0.2 kPa. Above 0.3 kPa a saturation in oxygen consumption was observed. Exposure to high oxygen pressures resulted in an irreversible loss of nitrogenase activity. The oxygen inhibition pattern was shown to be similar to that in other microaerophilic and anaerobic nitrogen-fixing microorganisms.

Metabolic quotient of the soil microflora in relation to plant succession.

In this study we propose the hypothesis that ecosystem succession is accompanied by a decrease in the metabolic quotient qCO2 (respiration-to-biomass ratio) of the soil microflora. The qCO2 is calculated from basal respiration (CO2-C·h-1) per unit microbial biomass carbon (Cmier). The hypothesis was tested by studying two primary successions on recessional moraines of the Rotmoos Ferner (Austria) and the Athabasca Glacier (Canada). For both soil seres (0->200 years) it was shown that the qCO2 decreased with time, which corroborated the hypothesis. In addition, the short term development of the qCO2 was demonstrated with a revegetation trial. We observed a rise in qCO2 for the first two years after reclamation, followed by a subsequent decrease.

Contribution of nitrogen fixation to nitrogen nutrition in an alpine sedge community (Caricetum curvulae).

In situ acetylene reduction assays (ARA) were carried out over two growing seasons at 2550 m in the upper alpine zone of the Tyrolean Central Alps of Austria. For comparative purposes, some Fabaceae species introduced into the upper alpine zone from lower elevation (2000 m) were subjected to ARA. At the end of the growing season the potted plants were transferred to the laboratory where their acetylene reducing activities were measured again. In situ nitrogenase activity is very low. The highest values were found in association with Leucanthemopsis alpina and Veronica bellidioides (150 and 217 nmol ethylene 24 h-1 per pot respectively). Higher levels of activity were detected in pots transferred to the laboratory (maximum value 750 nmol ethylene 24 h-1 per pot; assay temperature about 12°C higher than in the field) and in the Fabaceae transferred to the upper alpine zone (14×103 nmol ethylene 24 h-1 per pot of Trifolium badium and T. pallescens). Maximum nitrogen input in the field is in the range of 8 mg m-2 a-1. Therefore, under natural circumstances biological nitrogen fixation contributes only very small amounts of nitrogen to this alpine vegetation system, the process being inhibited by low soil temperatures. Possible alternative sources and patterns of N acquisition are discussed in relation to the overall nitrogen economics of plants of the upper alpine zone.

Availability of nitrogen and phosphorus in the nival zone of the Alps.

In high-alpine soils the maximum temperature is low even during the growing season, and hence mineralisation of nutrients is reduced. The aim of this study was to investigate what sources of nitrogen and phosphorus are available for vascular plants in the alpine nival zone to support growth. Using acetylene reduction assays levels of nitrogenase activity were assessed in sealed pots containing nival zone soil and plants at an altitude above 3000 m, and in bacterial isolates of soil and rhizosphere in the laboratory. Nitrogenase activity could not be detected in bacterial isolates or in the soil containing no plants. Small quantities of ethylen (<87 nmol·h-1 per pot) were detected in pots with Cerastium uniflorum and Poa laxa. This activity must be attributable to rhizosphere bacteria since no evidence for the presence of cyanobacteria could be obtained.Other sources of nitrogen for the plants were detected in the form of ammonium and nitrate in soil water and in snow melt water. These solutions also contained extractable phosphorus in quantities normally considered to be sufficient for growth. Analyses of the internal concentration of nitrogen and phosphorus also suggested that these elements were present in adequate amounts in these plants. It was considered that soil and snow melt water together may provide sufficient nitrogen and phosphorus to support the extremely small annual growth increment of nival zone plants.

[Microbial sources of antigens in the environment of farmer's lung patients (author's transl)]. / Mikrobielle antigenquellen in der Umgebung von Patienten mit farmerlunge.

The actinomycetes Micropolyspora faeni and Thermoactinomyces vulgaris are important sources of antigens in extrinsic allergic alveolitis, the deuteromycete Aspergillus fumigatus is it to a lesser extent. These microorganisms have been sought in hay samples obtained from farmers who on the one hand show farmer's lung symptoms and on the other antibodies to these microorganisms. A relatively good correlation has been found between the immunological and microbiological findings. The conditions necessary for the occurrence of antigen sources in farmer's lung disease are discussed, and the need for prophylactic measures is pointed out.

The significance of a root-fungus association in two Carex species of high-alpine plant communities.

The relationship between roots of Carex firma, C. sempervirens and their commonly occuring dark septate fungal associates was examined. Two typical fungal associates were isolated and reinoculated onto aseptically grown seedlings of the two host species. Both isolates produced significant increases of dry matter production in C. firma compared with uninoculated controls. No growth stimulation was obtained in C. sempervirens. Shoot phosphorus concentrations were significantly increased in both host species by inoculation. The absence of growth stimulation in C. sempervirens may be due to carbon drain imposed by the fungus or to the fact that nutrients other than phosphorus are growth limiting. The nature and possible ecological significance of the root-fungus association is discussed and it is suggested that the relationship is mutualistic rather than parasitic.

Fungal associations of roots of dominant and sub-dominant plants in high-alpine vegetation systems with special reference to mycorrhiza.

Types of root infection were analysed in healthy dominant and sub-dominant plants of zonal and azonal vegetation above the timberline in the Central and Northern Calcareous Alps of Austria. In the open nival zone vegetation, infection by fungi of the Rhizoctonia type was predominant, vesicular-arbuscular mycorrhizal infection, which was mostly of the fine endophyte (Glomus tenuis) type, being light and mainly restricted to grasses in closed vegetation patches. More extensive Glomus tenuis infection was found in the alpine grass heath, but in Carex, Rhizoctonia was again the most important fungus. The ericaceous plants of the dwarf shrub heath have typical ericoid infection, but quantitative analysis reveals a decrease of infection intensity with increase of altitude. The possible function of the various types of root infection are discussed, and the status of Rhizoctonia as a possible mycorrhizal fungus is considered.