Submitted to: Abstracts for New Phytologist Symposium
Publication Type: Abstract Only
Publication Acceptance Date: September 30, 2002
Publication Date: September 30, 2002
Uptake of heavy metals into hyperaccumulators is influenced by a number of chemical, physical and biological factors. Of these, recent evidence has shown that microbes living within the rhizosphere of hyperaccumulators may have a significant effect on metal uptake. Much is known about the role mycorrhizae play in metal uptake with most species generally reducing uptake from highly enriched soil. Much less is known about free living rhizosphere bacteria, especially since these organisms are often quite difficult to study. We have been using both cultural and genetic approaches to characterize hyperaccumulator rhizosphere populations. In general, we have found that all soil bacteria, whether rhizosphere competent or not, increase metal uptake into plants. This may simply be related to metabolic function and excretion of wastes into the rhizosphere. However, we have found specific bacteria within the rhizosphere of hyperaccumulators that preferentially increase metal uptake into plants at a much higher rate than microbes that do not colonize the rhizosphere of hyperaccumulators. For some bacteria, the increase in uptake can be up to 33% above that when plants are not inoculated with the specific bacterial strain. Studies are continuing to determine whether inoculation can be commercially applied during phytoremediation, and risk assessment studies are underway to assess the safety of this practice.