Plant root bacteria as a support for phytoremediation of heavy metal contaminated soil

Several heavy metal resistant strains were isolated from the soil/rhizosphere of spontaneous plants, growing in a highly polluted soil. One particularly resistant strain, growing on 7.5 mM CdCl2, was selected from the rhizosphere of a Brassica sp. plant. Phenotypic tests and 16S rDNA analysis enabled to identify the strain as Serratia plymuthica. The resistance mechanism proved to diverge from the czc system of Alcaligenes euthrophus, as shown through the use of a czc probe. Intracellular accumulation of Cd was occurring as determined by ICP analysis. The presence of the isolate in the rhizosphere of Brassica plants was supposed to be in connection with its ability to produce Plant Growth Promoting Compounds such as Indol-acetic acid. The use of members of Brassicaceae as heavy metal accumulating plants for phytoremediation purposes may therefore take advantage from the presence of this bacterial specie