1. Metale ciężkie – występowanie i toksyczność. 2. Bakteryjne mechanizmy oporności na metale ciężkie. 2.1. Modyfikacje osłon komórkowych uniemożliwiające wnikanie jonów metali do cytoplazmy. 2.2. Usuwanie jonów metali z cytoplazmy na zewnątrz komórki. 2.3. Enzymatyczna detoksyfikacja jonów metali. 2.4. Pozakomórkowe wiązanie jonów metali przez metabolity bakterii.
2.5. Wewnątrzkomórkowe wiązanie jonów metali. 3. Podsumowanie
Abstract: Bacteria play a substantial role in the biogeochemical cycles of metals, many of which exhibit toxicity towards various organisms. These unicellular bacteria are persistently exposed to the intoxication by heavy metals which are natural components of the environment. Intensive industrialization and extensive anthropogenic exploitation of the environment resulted in the release of heavy metals formerly deposed as minerals in rocks and as a consequence, in the pollution increase of all environmental constituents the soil, air and water. Bacteria have evolved various mechanisms of heavy metal resistance. The two most important mechanisms are: (i) heavy metal exclusion by the cellular barrier permeability and their immobilization outside the cell by bacterium metabolites, and (ii) the detoxification of toxic metal ions which entered the cytoplasm by different chemiosmotic and/or energy-dependent efflux systems as well as by intracellular sequestration mechanisms involving low molecular weight proteins such as cysteine-rich metallothioneins. The development of various mechanisms of heavy metal resistance enables bacteria to survive in harsh conditions and also allows us to apply them in the remediation of metal contaminated areas.
1. Heavy metals – their occurrence and toxicity. 2. Mechanisms of bacterial resistance to heavy metals. 2.1. Modifications of the cellular barrier preventing metal ion penetration into the cytoplasm. 2.2. Efflux of metal ions out of the cell. 2.3. Enzymatic conversion of metal ions. 2.4. Extracellular sequestration of metal ions by bacterial metabolites. 2.5. Intracellular sequestration of metal ions. 3. Summary