User:Milena Kovacevic/sandbox

Original - "Halorespiration"
= Halorespiration = Halorespiration or dehalorespiration is the use of halogenated compounds as terminal electron acceptors in anaerobic respiration. Halorespiration can play a part in microbial biodegradation. The most common substrates are chlorinated aliphatics (PCE, TCE), chlorinated phenols. Dehalorespiring bacteria are highly diverse. This trait is found in some proteobacteria, chloroflexi (green nonsulfur bacteria), low G+C gram positive Clostridia. and ultramicrobacteria.

Edit - "Halorespiration"
= Halorespiration = Halorespiration or dehalorespiration is the use of halogenated compounds as terminal electron acceptors in anaerobic respiration. Halorespiration can play a part in microbial biodegradation. The most common substrates are chlorinated aliphatics (PCE, TCE), chlorinated phenols. Dehalorespiring bacteria are highly diverse. This trait is found in some proteobacteria, chloroflexi (green nonsulfur bacteria), low G+C gram positive Clostridia. and ultramicrobacteria.

Process of Halorespiration
The process of dehalorespiration uses reductive dehalogenation to produce energy that can be used by the respiring microorganism to carry out its survival and metabolism. Reductive dehalogenation is when the halogen substituents are removed from a compound and replaced with electrons, resulting in the reduction of the compound. Hydrogenolysis and vicinal reduction are the two known processes of reductive dehalogenation. In hydrogenolysis, halogen substituents are substituted with hydrogen atoms. In vicinal reduction, also known as dihaloelimination, two halogen substituents on adjacent carbons are removed to form a double bond between the adjacent carbons. In both processes, the removed halogen substituents are released as anions. In dehalorespiration, the halogenated compounds are used as terminal electron acceptors, resulting in their dehalogenation, which is catalyzed by reductive dehalogenases. Reductive dehalogenases are a type of membrane-bound enzymes that contain iron-sulfur (Fe-S) clusters and a vitamin B12 cofactor at the active site. Although the exact mechanism of reductive dehalogenases is unknown, these two components of the enzyme are believed to be involved in the process of reductive dehalogenation, and are important in the reduction of pollutants such as trichloroethylene (TCE) and tetrachloroethylene (PCE).

Substrates Used and their Environmental Significance
Common substrates used as terminal electron acceptors in dehalorespiration are organochloride pesticides, aryl halides and alkyl solvents. Hydrogenolysis is able to degrade aryl halides and alkyl solvents, while vicinal reduction can only degrade alkyl solvents. Many of these are persistent and toxic pollutants that can only be degraded, either partially or completely, by dehalorespiration For example, PCE is an alkyl solvent that was previously used in dry cleaning and industrial applications  ; it remains a significant contaminant of ground water. Organisms that can completely degrade PCE into ethene, a nontoxic chemical, have been isolated. For these reasons, dehalorespiration is environmentally significant in bioremediation and its potential applications are an interest of research.

Milena Kovacevic (talk) 22:38, 8 October 2017 (UTC)

Final Edits - "Halorespiration"
= Halorespiration = Halorespiration or dehalorespiration is the use of halogenated compounds as terminal electron acceptors in anaerobic respiration. Halorespiration can play a part in microbial biodegradation. The most common substrates are chlorinated aliphatics (PCE, TCE), chlorinated phenols. Dehalorespiring bacteria are highly diverse. This trait is found in some proteobacteria, chloroflexi (green nonsulfur bacteria), low G+C gram positive Clostridia. and ultramicrobacteria.

Process of Halorespiration
The process of halorespiration, or dehalorespiration, uses reductive dehalogenation to produce energy that can be used by the respiring microorganism to carry out its growth and metabolism. Halogenated organic compounds are used as the terminal electron acceptor, which results in their dehalogenation. Reductive dehalogenation is the process by which this occurs. It involves the reduction of halogenated compounds by removing the halogen substituents, while simultaneously adding electrons to the compound. Hydrogenolysis and vicinal reduction are the two known processes of this mechanism that have been identified. In both processes, the removed halogen substituents are released as anions. Reductive dehalogenation has been shown to be catalyzed by reductive dehalogenases, which are membrane-bound enzymes. Most of these enzymes contain iron-sulfur (Fe-S) clusters, and a corrinoid cofactor at their active sites. Although the exact mechanism is unknown, research suggests that these two components of the enzyme may be involved in the reduction.

Substrates Used and Environmental Significance
Common substrates that are used as terminal electron acceptors in dehalorespiration are organochloride pesticides, aryl halides and alkyl solvents. Many of these are persistent and toxic pollutants that can only be degraded anaerobically by dehalorespiration, either partially or completely. Trichloroethylene (TCE) and tetrachloroethylene (PCE) are two examples of such pollutants, and their degradation has been a focus of research. PCE is an alkyl solvent that was previously used in dry cleaning, degreasing machinery and other applications. It remains a common contaminant of groundwater. Bacteria that are capable of completely degrading PCE to ethene, a nontoxic chemical, have been isolated. They have been found to belong to the Dehalococcoides genus and to use H2 as their electron donor. The process of dehalorespiration has been applied to in situ bioremediation of PCE and TCE in the past. For example, enhanced reductive dechlorination has been used to treat contaminated groundwater by introducing electron donors and dehalorespiring bacteria into the contaminated site, to create conditions that stimulate bacterial growth and dehalorespiration. In enhanced reductive dechlorination, the pollutants act as the electron acceptors and are completely reduced to ultimately produce ethene in a series of reactions.

Milena Kovacevic (talk) 22:59, 19 November 2017 (UTC)