User:Yasmine Chung/sandbox

Original- "Dissimilatory metal-reducing bacteria"

Conditions for dissimilatory metal reduction
DMRB include both obligate (strict) anaerobes, such as the Geobacteraceae family, and facultative anaerobes, such as Shewanella spp. Some species of DMRB produce compounds that act as electron shuttles, enabling them to perform metal reduction from a distance. Other organic compounds frequently found in soils and sediments, such as humic acids, may also act as electron shuttles.

Edits- "Dissimilatory metal-reducing bacteria"

Conditions for dissimilatory metal reduction
DMRB include both obligate (strict) anaerobes, such as the Geobacteraceae family, and facultative anaerobes, such as Shewanella spp. Due to the impermeability of the cell wall to minerals and the insolubility of metal oxides, DMRB have developed ways to reduce metals extracellulary via electron transfer. In addition to establishing direct contact, some DMRB display the ability to perform ranged metal reduction. For instance, some species of DMRB produce compounds that can dissolve insoluble minerals or act as electron shuttles, enabling them to perform metal reduction from a distance. Other organic compounds frequently found in soils and sediments, such as humic acids, may also act as electron shuttles. In biofilms, nanowires and multistep electron hopping (in which electrons jump from cell to cell towards the mineral) have also been suggested as methods for reducing metals without requiring direct cell contact.

-Yasmine Chung (talk) 18:34, 7 October 2017 (UTC)

Further edits- "Dissimilatory metal-reducing bacteria"

Conditions and mechanisms for dissimilatory metal reduction
Dissimilatory metal reducers are a diverse group of microorganisms, which is reflected in the factors that affect the different forms of metal reduction. The process of dissimilatory metal reduction occurs in the absence of oxygen, but DMRB include both obligate (strict) anaerobes, such as the Geobacteraceae family, and facultative anaerobes, such as Shewanella spp. As well, across the DMRB species, various electron donors are used in the oxidative reaction that is coupled to metal reduction. For instance, some species are limited to small organic acids and hydrogen, whereas others may oxidize aromatic compounds. In certain instances, such as Cr(VI) reduction, the use of small organic compounds can optimize the rate of metal reduction. Another factor that influences metal respiration is environmental acidity. Although acidophilic and alkaliphilic DMRB exist, the neutrophilic metal reducers group contains the most well-characterized genera. In soil and sediment environments, where the pH is often neutral, metals like iron are found in their solid oxidized forms, and exhibit variable reduction potential, which can affect their use by bacteria.

Due to the impermeability of the cell wall to minerals and the insolubility of metal oxides, DMRB have developed ways to reduce metals extracellulary via electron transfer. Cytochromes c, which are transmembrane proteins, play an important role in transporting electrons from the cytosol to enzymes attached to the outside of the cell. The electrons are then further transported to the terminal electron acceptor via direct interaction between the enzymes and the metal oxide. In addition to establishing direct contact, DMRB also display the ability to perform ranged metal reduction. For instance, some species of DMRB produce compounds that can dissolve insoluble minerals or act as electron shuttles, enabling them to perform metal reduction from a distance. Other organic compounds frequently found in soils and sediments, such as humic acids, may also act as electron shuttles. In biofilms, nanowires and multistep electron hopping (in which electrons jump from cell to cell towards the mineral) have also been suggested as methods for reducing metals without requiring direct cell contact. It has been proposed that cytochromes c are involved in both of these mechanisms. In nanowires, for instance, cytochromes c function as the final component that transfers electrons to the metal oxide.

-Yasmine Chung (talk) 23:33, 18 November 2017 (UTC)