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Summary 1. The ability of exotic plant species to establish and expand in new areas may be enhanced by a relatively high ability to acquire soil nutrients. To test this hypothesis, we predicted that the capacity for nutrient acquisition would be higher in seedlings of exotic species than in seedlings of native congeners. 2. We selected the five exotic species that had recently increased in abundance in a riverine habitat in the Netherlands and that had a native congener that was common in the same habitat. We grew seedlings of each of these ten species singly in pots of soil from this habitat in a glasshouse. After two months, we measured the final dry mass and N and P content of each plant and components of microbial biomass and nutrient mineralization in the soil. We also measured these soil characteristics in pots that had been left unplanted. 3. Exotic and native congeners did not differ consistently in the uptake of N or P or in effects on components of soil mineralization. Within a genus, values of these measurements were sometimes higher, sometimes lower and sometimes similar to the exotic when compared with the native species. 4. Depending upon the statistical analysis used, biomarker-based biomass of arbuscular mycorrhizal fungi was generally higher in soil planted with exotic than with native species. Most measures of microbial biomass and soil mineralization were higher in pots that had been planted with plants than in pots with no plant. 5. Synthesis. Our results do not suggest that invasive, exotic plant species generally possess greater capacity for nutrient acquisition during the early establishment than native species do. [ABSTRACT FROM AUTHOR]

Abstract: A field study was performed to examine whether an increased density of saprotrophic fungi in the rhizosphere selects for bacteria with traits advantageous to living in a fungal-rich environment. Fast-growing bacteria were isolated from the rhizosphere of Carex arenaria (sand sedge) plants growing in fungal-poor (sand drifts) and fungal-rich (forest) sites in the Netherlands and screened for several potential antifungal properties, namely in vitro antagonism and the production of siderophores, cyanide and lytic enzymes. A higher incidence of putatively antifungal traits was generally found in bacteria isolated from fungal-rich soils, thus supporting the hypothesis that high fungal densities can impose a selection pressure on rhizosphere bacteria. [Copyright &y& Elsevier]

A polyphasic approach was used to describe the phylogenetic position of 22 chitinolytic bacterial isolates that were able to grow at the expense of intact, living hyphae of several soil fungi. These isolates, which were found in slightly acidic dune soils in the Netherlands, were strictly aerobic, Gram-negative rods. Cells grown in liquid cultures were flagellated and possessed pili. A wide range of sugars, alcohols, organic acids and amino acids could be metabolized, whereas several di- and trisaccharides could not be used as substrates. The major cellular fatty acids were C(16 : 0), C(16 : 1)omega7c and C(18 : 1)omega7c. DNA G+C contents were 57-62 mol%. Analysis of nearly full-length 16S rDNA sequences showed that the isolates were related closely to each other (>98.6 % sequence similarity) and could be assigned to the beta-Proteobacteria, family 'Oxalobacteraceae', order 'Burkholderiales'. The most closely related species belonged to the genera Herbaspirillum and Janthinobacterium, exhibiting 95.9-96.7 % (Herbaspirillum species) and 94.3-95.6 % (Janthinobacterium species) 16S rDNA sequence similarity to the isolates. Several physiological and biochemical properties indicated that the isolates could be distinguished clearly from both of these genera. Therefore, it is proposed that the isolates described in this study are representatives of a novel genus, Collimonas gen. nov. Genomic fingerprinting (BOX-PCR), detailed analysis of 16S rDNA patterns and physiological characterization (Biolog) of the isolates revealed the existence of four subclusters. The name Collimonas fungivorans gen. nov., sp. nov. has been given to one subcluster (four isolates) that appears to be in the centre of the novel genus; isolates in the other subclusters have been tentatively named Collimonas sp. The type strain of Collimonas fungivorans gen. nov., sp. nov. is Ter6(T) (=NCCB 100033(T)=LMG 21973(T)).