Sulfur chemolithotrophic oxidizers

In this retrospective analysis of our current understanding of chemolithotrophic sulfur compound oxidation, I have sought to show how the hve research papers (and two reviews) on T. thioparus published by Peck and... 

In the presence of oxygen, abiotic oxidation of hydrogen sulfide can occur. However, this reaction can be catalyzed by sulfur-oxidizing bacteria (Figures 11.15 and 11.16). Oxidation of reduced sulfur occurs at interfaces the oxic-anoxic interface for abiotic and chemolithotrophic oxidation and, in the anoxic zone, the light-dark interface for phototrophic oxidation. 

Cork [283], Sublette [284], and others have identified a number of chemolithotrophic bacteria which oxidize elemental sulfur and use reduced or partially reduced sulfur compounds as an energy source, in the presence of various carbon sources (such as carbon dioxide or bicarbonate) and reduced nitrogen (e.g., ammonium ion). In the case of Cork et al. s work, the anaerobic photosynthetic bacterium Chlorobium thiosulfatophilum is used to convert sulfides to sulfate. The economics of this process was not favorable due to the requirement of light for the growth of the bacterium. 

Kelly DP. 1999. Thermodynamic aspects of energy conservation by chemolithotrophic sulfur bacteria in relation to the sulfur oxidation pathways. Arch Microbiol 171 219-29. 

Kelly DP, Wood AP. 1994. Whole organism methods for inorganic sulfur oxidation by chemolithotrophs and photolithotrophs. In Peck HD, LeGall J, editors. Inorganic microbial sulfur metabolism. Volume 243, Methods in enzymology. p 510-20. 

To return to the chemolithotrophs, there are species of sulfur bacteria that obtain energy from the oxidation of various stales of sulfur... 

Aerobic, chemolithotrophic bacteria. Colorless sulfur bacteria Thiobacillus iron or manganese-oxidizing bacteria, magnetotactic bacteria nitrifying bacteria Nitrobacter, Nitrosomonas... 

Sulfur fulfills many diverse roles in lakes. As the sixth most abundant element in biomass, it is required as a major nutrient by all organisms. For most algae, S is abundant in the form of sulfate in the water column however, in dilute glacial lakes in Alaska (I) and in some central African lakes (2) low concentrations of sulfate may limit primary production. Sulfur also serves the dual role of electron acceptor for respiration and, in reduced forms, source of energy for chemolithotrophic secondary production. Net sulfate reduction can account for 10-80% of anaerobic carbon oxidation in lakes (3-5), and hence this process is important in carbon and energy flow. Sulfate reduction, whether associated with uptake of sulfate and incorpo-... 

Chemolithotrophic organisms can oxidize inorganic substances such as HoS, elemental sulfur, or reduced nitrogen compounds, obtaining... 

Thiobacillus are acidophilic (they grow well at pH 2-3). They are obligate chemolithotrophs that obtain their energy exclusively from the oxidation of inorganic sulfur, and their carbon from the reduction of carbon dioxide. Most Thiobacillus are obligate aerobes, requiring 02 for the oxidation of the inorganic sulfur compounds. 

The chemoautotrophic fixation of C02 connected with this activity, only minimally contributes to the carbon cycling in most ecosystems. Notable exceptions to this include the deep-sea hydrothermal vent ecosystems, where the whole vent community is supported by the chemoautotrophic oxidation of reduced sulfur, primarily by Beggiatoa, Thiomi-cropira, and other sulfur oxidizers. In environments other than these, the generation of reduced minerals used in chemolithotrophic production is directly tied to the oxidation of photosynthetically produced organic matter. Therefore, sustainable primary production without solar energy input is unthinkable even in the case of chemolithotrophs. 

Rusticyanin is found in Thiobacillus ferrooxidans, an acidophilic, chemolithotrophic sulfur bacterium utilizing Fe + and reduced sulfur compounds as its sole energy source. T. ferrooxidans does not produce rusticyanin when grown on reduced sulfur. Similar to other substrate-inducible cupredoxms, the msticyanin gene is activated when soluble iron is present in the media. Little is known about its redox partners and it should be noted that rusticyanin itself does not carry out Fe + oxidation. Other iron-oxidizing bacteria, for example, Leptospirillum ferrooxidans, prodnce a cytochrome which substitutes rusticyanin functionally. To date T. ferrooxidans remains the only source for rusticyanin. 

Two classes of bacteria are specially adapted for sulfur oxidation (Table 6.1.2) Chemolithotrophic sulfur bacteria which utilize the energy released during oxidation by oxygen for fixation of CO2 into organic matter (e.g. eqn (2))... 

It is important to note that the autotrophic chemolithotrophs have a rather low growth yield (amount of biomass produced per mol of substrate consumed). For example, the sulfur bacteria use most of the electrons and energy from sulfide oxidation to generate ATP. They need this... 

Among the aerobic chemolithotrophs, colorless sulfur bacteria may oxidize H S, S , or FeS to... 

---