Frankia strains of soil under Betula pendula : Behaviour in soil and in pure culture
ABSTRACT The development of the nativeFrankia population was studied in a pot experiment in two types of soil; one from aBetula pendula Roth stand, with a high nodulation capacity, and one with a low nodulation capacity from aPinus sylvestris L. stand. The soils were kept at 22°C and 80% WHC. The capacity of the soils to form root nodules onAlnus incana (L.) Moench seedlings was followed over time. An increase in nodulation capacity was observed in the birch soil at pH 6 (attained
by liming). The increase was most pronounced when the soil was planted withBetula pendula seedlings. Nodulation capacity decreased in the birch soil at its original pH of 4.2, and in the pine soil (original pH 3.7),
irrespective of whether it was limed or planted.
Frankia strains were isolated fromAlnus incana root nodules, induced by soil samples from twoBetula pendula stands devoid of actinorhizal plants but showing a high nodulation capacity. The effect of various aqueous soil extracts
on the growth of the strains in propionate medium was studied. Extracts either inhibited or did not affect the growth of the
strains. No adaptation to normal soil pH and temperature conditions was found.
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Article: Measuring plant neighbour effectsFunctional Ecology 01/1996; 10:548-549. · 4.86 Impact Factor
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ABSTRACT: Bacterial growth in the rhizosphere and resulting changes in plant growth parameters were studied in small aseptic seedlings of birch (Betula pendula and B. pubescens) and grasses (Poa pratensis and Festuca rubra). The seedlings were inoculated with three Frankia strains (Ai1a and Ag5b isolated from native Alnus root nodules and Ai17 from a root nodule induced by soil originating from a Betula pendula stand), and three associative N2-fixing bacteria (Enterobacter agglomerans, Klebsiella pneumoniae and Pseudomonas sp., isolated from grass roots). Microscopic observations showed that all the Frankia strains were able to colonize and grow on the root surface of the plants tested without addition of an exogenous carbon source. No net growth of the associative N2-fixers was observed in the rhizosphere, although inoculum viable counts were maintained over the experimental period. Changes in both the biomass and morphology of plant seedlings in response to bacterial inoculation were recorded, which were more dependent on the plant species than on the bacterial strain.Plant and Soil 06/1993; 153(1):85-95. · 3.24 Impact Factor
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ABSTRACT: Application ofa high-performance liquid chromatography-based muramicacidassay withprecolumn fluorescence derivatization toquantification ofroot-associated bacteria was studied bothinpurecultures and intherhizosphere ofaxenic Festuca rubra seedlings. Quantities ofmuramicacidfromacid-hydrolyzed cells of Frankia strains, Streptomyces griseoviridis, Enterobacter agglomerans, Klebsiella pneumoniae, Pseudomonas sp., andBacillus polymyxa weremostly proportional totherespective cell protein andcarbon quantities, butinsome strains, culture age andparticularly sporulation affected these ratios considerably. Themuramicacid/cell protein ratio was generally 2 to4 timeshigher instrains ofthetwoactinomycete genera,Frankia and Streptomyces, thanintherestofthestrains. Quantification ofFrankia strains, S.griseoviridis, E.agglomerans, andPseudomonas sp.was alsoattempted fromtherhizosphere ofF.rubra seedlings whichhadbeeninoculated withpure cultured bacteria andincubated briefly. Itwas possible toquantify Frankia cells byuse ofthe muramic acid assayfromboththerootandthegrowth medium, whereas cells oftherestofthebacterial genera couldonlybedetected inthemedium. Thedetection limit formuramicacid was about10ng/mlhydrolysis volume, andfromtheFestuca rhizosphere, 28to63%ofthemuramicacidintheFrankia inoculum was recovered.