Browsing tag: metale ciężkie

Mechanizmy oporności bakterii na metale ciężkie

Mechanisms of heavy metals resistance in bacteria
E. Oleńska, W. Małek

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

Metalotioneiny bakteryjne

Bacterial metallothioneins
A. Mierek-Adamska, W. Tylman-Mojżeszek, Z. Znajewska, G. B. Dąbrowska

1. Wstęp. 2. Historia odkryć metalotionein u bakterii. 3. Budowa i sposób wiązania jonów metali ciężkich przez bakteryjne MT. 4. Funkcje metalotionein bakteryjnych. 5. Regulacja ekspresji bakteryjnych metalotionein. 6. Obecność metalotionein u bakterii. 7. Podsumowanie

Abstract: Heavy metals are found in all living organisms where, as indispensable microelements (e.g. zinc, iron, copper), are involved in endless metabolic processes. However, living organisms are also at a risk of exposure to highly toxic metals, including cadmium or lead, which do not play any physiological role. Among multiple mechanisms associated with the maintenance of micronutrient homeostasis and detoxification of unwanted metals, there is a family of low-molecular-weight, cysteine-rich proteins, able to chelate multiple metal ions i.e. the metallothioneins (MTs). They are widely distributed among Eucaryota, however, they have also been found in some limited Procaryota, including cyanobacteria, pseudomonads and mycobacteria. These bacterial MTs differ in terms of primary structure, the number and type of metal ions they bind, as well as with regard to their physiological functions. The expression of bacterial MTs is regulated by metals via metalosensors. MTs from cyanobacteria seem to be involved in zinc homeostasis, while in Pseudomonas they are linked to cadmium detoxification. In Mycobacterium, MTs bind copper ions and may play a pivotal role in the virulence of these bacteria. The presence of MTs in other groups of bacteria remains questionable. Problems with identification of new bacterial MTs are mainly associated with low level of homology between MT amino acid sequences of different bacterial groups. Further research is needed to evaluate the physiological functions of metallothioneins in Procaryota.

1. Introduction. 2. The history of discoveries of bacterial metallothioneins. 3. Structure and metal-binding properties of bacterial MTs. 4. Functions of bacterial metallothioneins. 5. Regulation of metallothionein gene expression. 6. Presence of metallothioneins in bacteria. 7. Summary

Rekultywacja gleb skażonych metalami ciężkimi metodą fitostabilizacji wspomaganej

Recultivation of heavy metal-contaminated soils using aided phytostabilization
D. Wasilkowski, A. Mrozik

1. Wprowadzenie. 2. Strategie tolerancji metali ciężkich u mikroorganizmów i roślin. 3. Koncepcja fitostabilizacji wspomaganej. 4. Aktywność mikrobiologiczna gleby w warunkach fitostabilizacji wspomaganej. 5. Wskaźniki mikrobiologiczne a jakość gleby. 6. Przykłady in situ fitostabilizacji wspomaganej. 7. Podsumowanie

Abstract: The main anthropogenic sources of heavy metals in the environment are mining and smelting, refining and chemical industry, industrial and municipal wastes, transport as well as fertilizers and pesticides used in agriculture. Among all heavy metals, Cd, Cu, Pb, Hg, Ni and Zn are of major environmental and human health concern. The high toxicity of heavy metals causes the need to remove them from the contaminated soil using minimally invasive remediation solutions, called gentle remediation options (GRO). One of the attractive methods to reduce the labile fractions and toxicity of heavy metals in soil seems to be aided phytostabilization. It is a combination of phytostabilization using plants tolerant to trace metals and stabilizing soil against erosion with the initial chemical immobilization achieved by adding various organic and inorganic additives. The potential toxicity of trace elements depends on their specific form present in the environment, their reactivity, mobility, concentration and their availability to living organisms. The bioavailability of heavy metals in soil is constantly changing and depends on different physicochemical, biological and environmental parameters. Due to the fact that microorganisms respond quickly to the presence of stressors in the environment, the changes in metabolic activity, size and structure can be used as good indicators of the effectiveness of applied remediation technology for cleaning up contaminated sites and ecosystem quality.

1. Introduction. 2. Tolerance strategies in microorganisms and plants. 3. Concept of aided phytostabilization. 4. Microbial activity of soil under aided phytostabilization. 5. Microbial indexes and soil quality. 6. Examples of in situ aided phytostabilization. 7. Summary