Lisa Stout
lstout@microbio.umass.edu

I am interested in how plant-microbe interactions may influence phytoremediation, specifically the removal of heavy metals from aquatic environments. My research focuses on microbial communities on the roots of Lemna minor, a small floating aquatic plant, and the community response to heavy metals such as cadmium. We have chosen Rice City Pond, an impoundment of the Blackstone River in Uxbridge, MA, as a study site. Historically, textile mill wastes contributed to the heavy metal pollution at this site (1); today, contamination originates mostly from urban runoff, although sediments are constantly disturbed, releasing heavy metals into the surface water. While surface water concentrations of metals are low compared to sediments, they are still of concern to aquatic life.

In our studies, we examine root surface bacterial communities from Lemna minor collected at Rice City Pond, in the presence and absence of additional cadmium. We also compare these microbial communities to those from Lemna minor with no previous exposure to cadmium.

We also study the abilities of plants with associated bacterial communities to accumulate metals compared to plants with no associated bacteria. We compare growth and metal accumulation in plants that have been sterilized to those that have not been sterilized, as well as determining the effects of adding certain bacteria with known metal resistance to sterilized plants.

Ultimately, we are interested in understanding what conditions allow plants to optimally remove metals. Associated bacteria may influencee metal uptake in plants by stimulating production of metal uptake compounds or transporters in plants, increasing root surface area, or making metals more bioavailable to plants(2).

Conditions that could influence plant-microbe associations include pH, nutrient availability, and temperature, to name a few. .

Rice City Pond with Lemna minor in the foreground



Bacteria on plant root stained with Syto-9



Sampling at Rice City Pond, Uxbridge, MA