The establishment of an introduced community of fluorescent pseudomonads in the soil and in the rhizosphere is affected by the soil type

Indigenous populations of fluorescent pseudomonads were previously shown to vary in two different soils (Chateaurenard and Dijon) and in the rhizosphe re of a plant species (Linum usitatissimum L.) cultivated in these two soil s. These differences could be related to the soil type and to their crop hi story. In the present study, the influence of the soil type on the diversit y of fluorescent pseudomonads in bulk and rhizospheric soils was evaluated. The soils of Chateaurenard and Dijon were sterilized before being inoculat ed with the same community of fluorescent pseudomonads. Bacterial isolates from bulk and rhizospheric soils were characterized on the basis of their r epetitive extragenic palindromic-PCR patterns allowing the comparison of th e distributions of the introduced populations. The influence of the soil ty pe on the establishment of the introduced bacterial community was recorded in the two bulk soils. Indeed, the density and the structure of the communi ty differed significantly between the two soils. The rhizosphere effect was also affected by the soil type. This effect was expressed in the Chateaure nard soil but not in the Dijon soil. Hence, the structure of the bacterial community associated with the tools of the same plant species cultivated in the two soils differed significantly. (C) 1999 Federation of European Micr obiological Societies. Published by Elsevier Science B.V. All rights reserv ed.