Final answer:
The statement is true; metal-reducing Geobacter and Shewanella species play a significant role in microbial mining of metals and in environmental bioremediation processes.
Step-by-step explanation:
Metal-reducing Geobacter and Shewanella species are indeed important in the microbial mining of metals, making the statement true. These microorganisms have the ability to reduce metals through their metabolic processes. This capability is particularly valuable in the context of microbial bioremediation, a process where microorganisms are used to remove pollutants, including toxic metals, from the environment.
For instance, some bacteria, including Geobacter and Shewanella, can transform soluble metal ions into less soluble or insoluble forms that are less harmful to the environment. Additionally, some Delta Proteobacteria, which include Geobacter, are known to reduce sulfate and sulfur as part of their respiration process. This diverse metabolic capacity of prokaryotes, including bacteria and Archaea, has significant environmental implications and is leveraged for bioremediation and bioenergy applications.