Mechanism of Bacterial Resistance to Chromium Heavy Metals
Signal reception systems in bacteria belonging to low-level organisms are still categorized as simple when compared to high-level organisms with more complex nervous system devices such as animals. Therefore, the way the bacterial response to environmental factors around will be different.
The response of animals when in dangerous conditions will move to a safer place. This does not apply to bacteria that have a narrower movement ability. Bacteria will carry out a series of activities to reduce their impact. For example, these two living things are around the area of ex-mining land which has a very high content of heavy metal chromium (Cr) and is toxic.
Also read : Ngaacik water in the old Kutai, philosophy to always "back to origin"
One characteristic of the area contaminated with heavy metal Cr (VI) is one that is not found in plants that thrive and tend to be dwarf-sized. Animals of herbivorous groups will be starved if they continue to be in this region. The message conveyed by this environment is delivered by the nervous system in animals to produce a response to move towards greener areas. Bacteria whose surface habitat and in the soil will experience direct contact with Cr (VI). This condition triggers bacteria to carry out a series of defenses starting from when Cr (VI) is in front of the cell membrane until when Cr (VI) has entered the bacterial cell.
The mechanism of transfer, resistance and reduction of Cr (VI) in bacterial cells. (a) a sulfate transport system which is also used as an entry point for Cr (VI) into cells. (b) Reduction of Cr (VI) to Cr (III) which is more environmentally friendly extracellularly, where chromium does not cross the cell membrane. (c) Chromate reductase enzyme that is bound to the cell membrane. (d) Intracellular reduction of Cr (VI) to Cr (III), but can trigger oxidative stress which causes damage to proteins and DNA. (e) Removal of Cr (VI) from the cytoplasm with the help of ChrA protein. (f) Detoxifying enzymes to protect cells from oxidative stress. (g) DNA repair system for damage triggered by chromium. (Joutey et al., 2015).
Bacterial defense against Cr (VI) includes resistance and reduction capabilities. Resistance to Cr (VI) includes the ability of bacteria to release Cr (VI) through protein channels, namely the sulfate transport system embedded in the cell membrane. The channel protein can be used Cr (VI) as an entry point when it is chromate (CrO42-) which resembles sulfate (SO42-). Chromate (CrO42-) entering will be released directly through the sulfate transport system. CrO42 - can also enter bacterial cells when the concentration is too high. CrO42 - which enters the cell can still be anticipated through the efflux system where CrO42 - is released from the cytoplasm to the protein channel in the cell membrane, ChrA.
The mechanism of bacterial reduction differs from resistance in terms of its ability to convert Cr (VI) to Cr (III) which has a lower toxicity level. The reduction stage of Cr (VI) generally involves the role of the chromate reductase enzyme which can be inductive (produced when there are triggers of Cr (VI)) or constitutive (produced continuously).
The work location of the chromate reductase enzyme is also classified into three namely in the cell cytoplasm (intracellular), bound to the cell membrane, and outside the cell (extracellular). The flow of enzymatic reactions that occur in the cell cytoplasm (intracellular) begins when CrO42 - which enters the cell changes into its initial form, Cr (VI). This dangerous form of Cr (VI) is responded by bacterial cells by producing the enzyme chromate reductase. During the process of reducing Cr (VI) in the cell it can trigger oxidative stress because Cr (VI) is a free radical. This stress can be overcome with antioxidant enzymes such as glutathione catalase.
The second enzymatic reaction is that which binds to the membrane. The mechanism of action of the chromate reductase enzyme on the membrane is when Cr (VI) is on the surface of the bacterial cell and will be reduced to Cr (III). Enzymatic reactions can also occur extracellularly when cells receive signals of the presence of CrVI) around. Cells will release chromate reductase enzymes into the environment and convert Cr (VI) to Cr (III). Cr (III) is environmentally friendly because the level of solubility in water is lower so that its mobility to invade other living things is also low.
Also Read : The exotic 'Desert' of Oetune Beach, Timor Tengah Selatan
Based on the various capabilities of bacteria in carrying out defenses against Cr (VI), extracellular reduction is considered the most effective mechanism for bacteria to survive. This is based on the ability of bacteria to prevent the entry of Cr (VI) into the cell and be able to convert it to Cr (III) directly in the environment.
Author: Ayesha
References: Joutey, N. T., H. et al. 2015. Mechanisms of Hexavalent Chromium Resistance and Removal by Microorganisms. Springer International Publishing Switzerland.
The response of animals when in dangerous conditions will move to a safer place. This does not apply to bacteria that have a narrower movement ability. Bacteria will carry out a series of activities to reduce their impact. For example, these two living things are around the area of ex-mining land which has a very high content of heavy metal chromium (Cr) and is toxic.
Also read : Ngaacik water in the old Kutai, philosophy to always "back to origin"
One characteristic of the area contaminated with heavy metal Cr (VI) is one that is not found in plants that thrive and tend to be dwarf-sized. Animals of herbivorous groups will be starved if they continue to be in this region. The message conveyed by this environment is delivered by the nervous system in animals to produce a response to move towards greener areas. Bacteria whose surface habitat and in the soil will experience direct contact with Cr (VI). This condition triggers bacteria to carry out a series of defenses starting from when Cr (VI) is in front of the cell membrane until when Cr (VI) has entered the bacterial cell.
The mechanism of transfer, resistance and reduction of Cr (VI) in bacterial cells. (a) a sulfate transport system which is also used as an entry point for Cr (VI) into cells. (b) Reduction of Cr (VI) to Cr (III) which is more environmentally friendly extracellularly, where chromium does not cross the cell membrane. (c) Chromate reductase enzyme that is bound to the cell membrane. (d) Intracellular reduction of Cr (VI) to Cr (III), but can trigger oxidative stress which causes damage to proteins and DNA. (e) Removal of Cr (VI) from the cytoplasm with the help of ChrA protein. (f) Detoxifying enzymes to protect cells from oxidative stress. (g) DNA repair system for damage triggered by chromium. (Joutey et al., 2015).
Bacterial defense against Cr (VI) includes resistance and reduction capabilities. Resistance to Cr (VI) includes the ability of bacteria to release Cr (VI) through protein channels, namely the sulfate transport system embedded in the cell membrane. The channel protein can be used Cr (VI) as an entry point when it is chromate (CrO42-) which resembles sulfate (SO42-). Chromate (CrO42-) entering will be released directly through the sulfate transport system. CrO42 - can also enter bacterial cells when the concentration is too high. CrO42 - which enters the cell can still be anticipated through the efflux system where CrO42 - is released from the cytoplasm to the protein channel in the cell membrane, ChrA.
The mechanism of bacterial reduction differs from resistance in terms of its ability to convert Cr (VI) to Cr (III) which has a lower toxicity level. The reduction stage of Cr (VI) generally involves the role of the chromate reductase enzyme which can be inductive (produced when there are triggers of Cr (VI)) or constitutive (produced continuously).
The work location of the chromate reductase enzyme is also classified into three namely in the cell cytoplasm (intracellular), bound to the cell membrane, and outside the cell (extracellular). The flow of enzymatic reactions that occur in the cell cytoplasm (intracellular) begins when CrO42 - which enters the cell changes into its initial form, Cr (VI). This dangerous form of Cr (VI) is responded by bacterial cells by producing the enzyme chromate reductase. During the process of reducing Cr (VI) in the cell it can trigger oxidative stress because Cr (VI) is a free radical. This stress can be overcome with antioxidant enzymes such as glutathione catalase.
The second enzymatic reaction is that which binds to the membrane. The mechanism of action of the chromate reductase enzyme on the membrane is when Cr (VI) is on the surface of the bacterial cell and will be reduced to Cr (III). Enzymatic reactions can also occur extracellularly when cells receive signals of the presence of CrVI) around. Cells will release chromate reductase enzymes into the environment and convert Cr (VI) to Cr (III). Cr (III) is environmentally friendly because the level of solubility in water is lower so that its mobility to invade other living things is also low.
Also Read : The exotic 'Desert' of Oetune Beach, Timor Tengah Selatan
Based on the various capabilities of bacteria in carrying out defenses against Cr (VI), extracellular reduction is considered the most effective mechanism for bacteria to survive. This is based on the ability of bacteria to prevent the entry of Cr (VI) into the cell and be able to convert it to Cr (III) directly in the environment.
Author: Ayesha
References: Joutey, N. T., H. et al. 2015. Mechanisms of Hexavalent Chromium Resistance and Removal by Microorganisms. Springer International Publishing Switzerland.
Post a Comment