Biological activity and colonization pattern of the bioluminescence-labeled plant growth-promoting bacterium Kluyvera ascorbata SUD165/26

Kluyvera ascorbata SUD165/26 is a spontaneous siderophore-overproducing mut ant of K. ascorbata SUD165, which was previously isolated from nickcl-conta minated soil and shown to significantly enhance plant growth in soil contam inated with high levels of heavy metals. To develop a better understanding of the functioning of K. ascorbata SUD 165/26 in the environment, and to tr ace its distribution in the rhizosphere, isolates of this bacterium were la beled with tither green fluorescent protein or luciferase. When the plant g rowth-promoting activities of the labeled strains were assayed and compared with the activities of the unlabeled strain, none of the monitored paramet ers had changed to any significant extent. When the spatial colonization pa tterns of the labeled bacteria on canola roots were determined after seed a pplication, it was observed that the bacterium was rightly attached to the surface of both roots and seeds, and formed aggregates. The majority of the bacterial population inhabited the upper two thirds of the roots, with no bacteria detected around the root tips. (C) 2001 Federation of European Mic robiological Societies. Published by Elsevier Science B.V. All rights reser ved.