Only two http://www.selleckchem.com/products/Dasatinib.html examples of quantification of the exchange of heavy metals (lead and cadmium) with ocean currents between one specific ocean, the Arctic Ocean, and neighbouring oceans was identified. These examples suggest that ocean transport may be an important pathway. In addition, the presence of cadmium in ammonium and phosphorus fertilizers is other important entry route of cadmium into the soil [7,8]. The chemistry of cadmium is to a great extent controlled by pH. Cadmium may be adsorbed on clay minerals, carbonates or hydrous oxides of iron and manganese or may be precipitated as cadmium carbonate, hydroxide, and phosphate. Under acidic conditions cadmium solubility increases, and very little adsorption of cadmium by soil colloids, hydrous oxides, and organic matter takes place.
Both toxicity and bioavailability of cadmium are influenced by soil characteristics. Although cadmium is ranked as non-essential heavy metal, it is already toxic to plants, animals and humans at low doses and acts as a cumulative poison [9,10]. Some cadmium compounds are relatively water soluble, mobile in soil and bioavailable, depending on the water and soil chemistries. It tends to bioaccumulate in organs such as the kidney and liver of vertebrates, but aquatic invertebrates and algae can also build up relatively high concentrations. Effects on birds and mammals are mainly due to kidney damage. In sea birds and marine mammals in particular, cadmium accumulates to relatively high levels. Microorganisms are very prone to such accumulation, however, this phenomenon makes it possible to use some microorganisms as a biosensor for detection of selected substances contaminating the environment [10].
The mechanisms of metal accumulation by microorganisms are summarized in Figure 1: (1) metal resistance of microbes is accomplished by intra- and extracellular mechanisms; (2) metals can be excreted via efflux transport systems; (3) sequestering compounds of the cytosol can bind and detoxify metals inside the cell; (4) the release of chelators into the extracellular milieu leads to bound and fixed metals; (5) the structure of the cell envelope is prone to bind large amounts of metals by sorption thus preventing influx [11]. Anacetrapib A great number of heavy metal resistant bacteria such as Cupriavidus metallidurans and others, is known to possess efflux transporters that excrete toxic or overconcentrated metals [12�C15].
Figure 1.Overview of bacteria cadmium interaction. (A) Cd(II) ions occur in environment (soil, water, biota); (B) Sorption of Cd(II) on the surface of bacterial wall (protein, cyrbohydrates); (C) ion transporter (metal transporting system��MIT, which enable …For metal ions to have physiological or toxic effects, they must enter the bacterial cell. Microbial selleck inhibitor uptake systems have to be tightly controlled to be able to differentiate between structurally very similar metal ions.