Industrial activities, such as mining, have contaminated large amounts of potentially arable land with heavy metals. This contamination is a significant environmental problem as heavy metals persist in the soil and can bioaccumulate within an ecosystem unless physically removed. Phytoremediation is a process that uses heavy metal hyper-accumulating (HMH) plants to extract heavy metals from the soil and sequester them into the leaf vacuoles. Unfortunately this process faces efficiency problems and is not yet commercially viable.
In heavy metal contaminated soils it is hypothesised that rhizosphere-associated microbes are important for plant health as well as heavy metal uptake. Currently little is known regarding microbial competition in the rhizosphere of HMH within heavy metal contaminated soils. To investigate the influence of microbial competition on the structure of the HMH rhizosphere, twenty microbial isolates from the HMH Carprobrotus rossi (Pigface) were utilised in competition and colonisation rhizosphere assays. These isolates allowed the testing of the roles of competition and selection in determining the microbial composition of the rhizosphere community in HMH.
The function of the microbial-rhizosphere associated community was further investigated through the development of new protocols for detection of whole soil associated community production of growth-promoting substances such as indole-3-acetic acid (auxin), ACC deaminase and siderophores. These assays provide a snap shot of the activity of the entire rhizosphere community function. These experiments will help provide information on the microbe-plant interactions within the rhizosphere of HMH that could lead to improved phytoremediation efficiency.