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The oxidation of reduced sulfur compounds is performed exclusively by Bacteria and Archaea.All the Archaea involved in this process are aerobic and belong to the Order Sulfolobales, [19] [20] characterized by acidophiles (extremophiles that require low pHs to grow) and thermophiles (extremophiles that require high temperatures to grow).
Most species oxidize sulfur compounds for energy metabolism. They often use nitrate as an electron acceptor, which contributes to the detoxification of sulfide-rich environments. These bacteria thrive when there is a gradient between oxygenated and anoxic zones, that can occur around hydrothermal vents.
Sulfur is metabolized by all organisms, from bacteria and archaea to plants and animals. Sulfur can have an oxidation state from -2 to +6 and is reduced or oxidized by a diverse range of organisms. [1] The element is present in proteins, sulfate esters of polysaccharides, steroids, phenols, and sulfur-containing coenzymes. [2]
Acidithiobacillus is a genus of the Acidithiobacillia in the phylum "Pseudomonadota".This genus includes ten species of acidophilic microorganisms capable of sulfur and/or iron oxidation: Acidithiobacillus albertensis, Acidithiobacillus caldus, Acidithiobacillus cuprithermicus, Acidithiobacillus ferrianus, Acidithiobacillus ferridurans, Acidithiobacillus ferriphilus, Acidithiobacillus ...
Thiothrix is a genus of filamentous sulfur-oxidizing bacteria, related to the genera Beggiatoa and Thioploca. They are usually Gram-negative (but can be Gram-variable) and rod-shaped (0.7–1.5 μm in width by 1.2–2.5 μm in length). They form ensheathed multicellular filaments that are attached at the base, and form gonidia at their free end.
Oxygen is required in both ammonia and nitrite oxidation, meaning that both nitrosifying and nitrite-oxidizing bacteria are aerobes. As in sulfur and iron oxidation, NADH for carbon dioxide fixation using the Calvin cycle is generated by reverse electron flow, thereby placing a further metabolic burden on an already energy-poor process.
An important distinction can be made between sulfur-oxidizing and nitrifying bacteria by their response to the introduction of carbon to the culture in the form of carbonates and bicarbonates. [2] Carbonates keep the medium alkaline , thus preventing growth of A. thiooxidans which grows best under acidic conditions, while bicarbonates have been ...
The capability to oxidize sulfide and store sulfur are the main features which define Beggiatoa and its close relative Thioploca as filamentous colorless sulfur bacteria, in contrast to other filamentous bacteria like cyanobacteria and the non-sulfur-oxidizing Cytophaga and Flexibacter. [11]