Desulfovibrio is a sulfate reducing bacteria, Thiobacillus is a sulfur oxidizing

Question

Desulfovibrio is a sulfate reducing bacteria, Thiobacillus is a sulfur oxidizing bacteria, and Methanobacterium is a chemolithotrophic methanogenic bacterium. Distinguish among these organisms. In your discussion you must include how each organism derives energy from its substrate, how the bioenergetics of these microbes are similar, the environment in which they exist, and how p, , and G"is poised against the AGp! You do not have to explain this mathematically or with equations. If diagrams will help, please provide. (10pts)

Explanation / Answer

Sulfate reducing bacteria (SRB) Sulfate-reducing bacteria (SRB) are thosebacteria and archaea that can obtain energy by oxidizing organic compounds whilereducing sulfate (SO42-) to hydrogen sulfide (H2S).In a sense, these organisms "breathe" sulfate rather than oxygen by anaerobic respiration.

The genus Thiobacillus comprises aerobic bacteria strains that thrive predominantly in pH-neutral environments. Some of these bacteria, however, flourish in highly acidic environments and can oxidize iron to obtain energy, which can damage surrounding habitats. For example, this becomes a problem in mining operations when bacteria oxidize coal spoil piles. They produce sulfuric acid during this process -- commonly known as acid mine drainage. These bacteria can also corrode gas pipelines. The most common strains of Thiobacillus are thioparus, denitrificans, thiooxidans, intermedius and ferrooxidans.

The methane-producing bacteria Methanobacteria are relatively unstudied group of bacteria that make up one of the larger divisions of the archaebacteria. Most methanogens will use H2 plus CO2 as the major or sole source of carbon for energy generation and cell material. A variety of techniques and media for the growth of these strict anaerobes have been described previously. Most notably, a recent technical advance with tubes or bottles pressurized with the substrate H2-CO2 has facilitated small-scale growth of these bacteria; this system involves using 02-free medium reduced with Na2S or cysteine to assure strict anaerobic condition; titanium-citrate and titanium-nitrilotriacetate have also been used in medium reduction . However, large-scale growth in fermentors routinely involves a bubbling gas system in which H2S is slowly flushed from the medium, causing an ultimate slowing of growth unless sulfide is re-added. Further, the H2S presents a great odor problem in the laboratory during both growth and harvesting.

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