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B Söderström

Publications and source records attributed to B Söderström.

11 recordsLinked to original sources
PubMed1999

Ammonium and methylamine transport by the ectomycorrhizal fungus Paxillus involutus and ectomycorrhizas.

Using [(14)C]methylamine as an analogue of ammonium, the kinetics and the energetics of NH(4)(+) transport were studied in the ectomycorrhizal fungus, Paxillus involutus (Batsch) Fr. The apparent half-saturation constant (K(m)) and the maximum uptake rate (V(max)) for the carrier-mediated transport derived from the Eadie-Hofstee transformation were 180 µM and 380 nmol (mg dry wt)(-1) min(-1,) respectively. Both pH dependence and inhibition by protonophores indicate that methylamine transport in P. involutus was dependent on the electrochemical H(+) gradient. Both long-term and short-term uptake experiments were consistent with regulation of ammonium/methylamine transport processes by the presence of an organic nitrogen source. Analysis of methylamine uptake by different P. involutus isolates revealed no obvious trend in the uptake capacities in relation to N deposition at the collection site. Kinetic parameters were determined in P. involutus/Betula pendula (Roth.) axenic association and in detached mycorrhizal roots isolated from forest sites. Enhanced methylamine uptake in the presence of the fungal symbiont was demonstrated. Homogeneous V(max) values were found for axenic and detached mycorrhizas, whereas K(m) values showed greater variations.

Journal Article↗
PubMed1994

Respiration of [14C]alanine by the ectomycorrhizal fungus Paxillus involutus.

The ectomycorrhizal fungus Paxillus involutus efficiently took up exogenously supplied [14C]alanine and rapidly converted it to pyruvate, citrate, succinate, fumarate and to CO2, thus providing direct evidence for the utilisation of alanine as a respiratory substrate. [14C]alanine was further actively metabolised to glutamate, glutamine and aspartate. Exposure to aminooxyacetate completely suppressed 14CO2 evolution and greatly reduced the flow of carbon from [14C]alanine to tricarboxylic acid cycle intermediates and amino acids, suggesting that alanine aminotransferase plays a pivotal role in alanine metabolism in Paxillus involutus.

Agaricales↗
PubMed1984

Separation of fungal propagules by partition in aqueous polymer two-phase systems.

Conidia of Penicillium chrysogenum and Penicillium frequentans and sporangiospores of Rhizopus rhizopodiformis, Rhizomucor pusillus, and Mucor racemosus were subjected to partition in aqueous polymer two-phase systems. The partition behavior differed drastically between the conidia of the two Penicillium species and the sporangiospores of the three species of phycomycetes. This difference in partition behavior can be used for purification of fungi belonging to different taxonomical groups. P. frequentans was completely separated from M. racemosus by two extractions, whereas four extractions were needed to purify M. racemosus. This method was used on an air sample from a locality where wood fuel chips are handled. The conidia of the fungi Trichoderma viride and Rhizopus rhizopodiformis were removed completely by only two extractions.

Journal Article↗
PubMed1983

Microfungi and microbial activity along a heavy metal gradient.

Soil fungal biomass, microfungal species composition, and soil respiration rate of conifer mor soil were studied along a steep copper and zinc gradient (up to 20,000 mug of Cu and 20,000 mug of Zn g dry soil) around a brass mill near the town of Gusum in South Sweden. Fungal biomass and soil respiration rate decreased by about 75% along the metal gradient. Above 1,000 mug of Cu g, the decrease was clearly evident; below 1,000 mug of Cu g, no obvious effects were observed, but there was a tendency for a decrease in total mycelial length. No decrease in CFU was found along the gradient, but fungal species composition was drastically changed. The frequency of the genera Penicillium and Oidiodendron decreased from about 30 and 20%, respectively, at the control sites to only a few percent close to the mill. Mortierella was most frequently isolated in moderately polluted sites, but at the highest pollution levels, a decrease in isolation frequency was evident. Some fungal taxa increased in abundance towards the mill, e.g., Geomyces (from 1 to 10%), Paecilomyces (0 to 10%), and sterile forms (from 10 to 20%). Analyses with a multivariate statistical method (partial least squares) showed that organic matter content and soil moisture had little influence on the fungal community compared with the heavy metal pollution.

Journal Article↗
PubMed1979

Classification of fungi by means of pyrolysis-gas chromatography-pattern recognition.

Repetitive samples of three strains of the mould Penicillium were subjected to pyrolysis-gas chromatography (Py-GC). From the chromatograms, 26 peak heights were used in a subsequent SIMCA pattern recognition analysis. This data analysis gives a marked improvement in the classification of the samples (100% correct, 85% unique) in comparison with the traditional analysis based on the average chromatogram of each class (92% correct, 45% unique). The data analytical method is described in detail using the Py-GC data as an illustration.

Analysis of Variance↗