Chapter 21 - Microorganisms and Metal Pollutants

Abstract

This chapter discusses metal–microbe interactions including mechanisms of metal resistance, effects of metal–microbe interactions, and applications of microorganisms to metal mining and remediation of metal-contaminated sites. The most common way microorganisms deal with excess metal is to pump the metal ions out and restrict uptake at the same time, or some have developed mechanisms to sequester and immobilize metals, whereas others enhance metal solubility in the environment. The toxicity effects of metals on the microbial cells include disruption of proteins and nucleic acids, with the result their function is impaired. The mechanisms of metal resistance and detoxification may be divided into three categories: (1) general resistance mechanisms that do not require metal stress, (2) general resistance mechanisms that are activated by metal stress, and (3) resistance mechanisms that are dependent on a specific metal for activation. Various methods for studying metal–microbial interactions have been developed and include culturing of metal resistant microorganisms in the medium and measurement of total, soluble, and bioavailable metal. Several proposed methods for microbial remediation of metal-contaminated soils are microbial leaching, use of microbial surfactants, microbially induced metal volatilization, and microbial immobilization and complexation. The microbial mechanisms can effectively remove metals from contaminated aquatic systems; however, the metals are not destroyed and still have to be properly disposed of.