Methane bacteria examples

The possible relationship of the methane fermentation with the more conventional examples of one-carbon metabolism as catalyzed by folate and vitamin B12 cofactors has been long apparent. 5-Methyl tetrahydro-folate, 5,10-methylene tetrahydrofolate, and methyl vitamin B12 are converted to methane by cell-free extracts of M. barkeri 32) and M. omeli-anskii (33). The involvement of vitamin B12 is further implicated by its high cellular level in methane bacteria and by the isolation of B12-containing proteins in extracts of M. barkeri 30) which stimulate methane evolution from methyl vitamin B12. The components and pathways that can be demonstrated in cell-free M. barkeri extracts 32) are listed below. 

Locating deposits of bitumens on the basis of geomicrobiological methods — for example the occurrence of methane bacteria can indicate natural gas, propane bacteria indicate the presence of petroleum, and similarly for bacteria utilizing butane, pentane and hexane. 

In some cases, microorganisms can transform a contaminant, but they are not able to use this compound as a source of energy or carbon. This biotransformation is often called co-metabolism. In co-metabolism, the transformation of the compound is an incidental reaction catalyzed by enzymes, which are involved in the normal microbial metabolism.33 A well-known example of co-metabolism is the degradation of (TCE) by methanotrophic bacteria, a group of bacteria that use methane as their source of carbon and energy. When metabolizing methane, methanotrophs produce the enzyme methane monooxygenase, which catalyzes the oxidation of TCE and other chlorinated aliphatics under aerobic conditions.34 In addition to methane, toluene and phenol have been used as primary substrates to stimulate the aerobic co-metabolism of chlorinated solvents. 

Siderophores are iron-complexing compounds of low molecular weight that are synthesized by bacteria and fungi, and serve to deliver iron to the microbes. Because of their exclusive affinity and specificity for Fe3+, natural siderophores and synthetic derivatives have been exploited in the treatment of human iron-overload diseases. The most successfully used example is Desferal , which is the methane sulfonate derivative of iron-free ferrioxamine B, a linear trihydroxamate (Figure 3.2). Ferrioxamine was isolated in 1958 from the culture supernatant of Streptomyces... 

Any of the above-mentioned compounds can be found and even synthesized in soil. The simplest example, methane (CH4), is commonly found in the soil atmosphere, ft is produced during the decomposition of organic matter under anaerobic conditions, which can occur even in aerobic soils. It is interesting to note that methane can not only can be produced in aerobic soils but can also be oxidized by soil bacteria in the same soil. 

To ensure that the anaerobic bacteria thrive, careful control over substrate concentration, pH, temperature, nutrients and toxins must be maintained. For example, acetate concentrations above 2 g/L and ammonia concentrations above 3 g/L will significantly diminish methane production. Oxygen and certain metals and antibiotic contaminants can be harmful. 

Nickel enzymes are particularly prominent in the metabolism of anaerobic bacteria. For example, the methanogenic bacteria, which are classified as Arch-aea, an ancient division of living organisms, can grow on a mixture of H2 and C02 to produce methane [9-11], The metabolism of methanogens involves three... 

Much effort has been concentrated on the fate of chlorinated aliphatic hydrocarbons in aquifers (e.g., trichloroethylene, dichloroethylene). These chemicals undergo reductive dehalogenation under anaerobic conditions. By contrast, these compounds are degraded under aerobic conditions by methane-utilizing bacteria. For example, methan-otrophic bacteria can transform more than 50% of trichloroethane into CO2 and bacterial biomass. 

Methylotropic bacteria (for example Methylomonas methardca) will hydroxylate aromatics when methane or the like is also provided as a carbon source, and as in the case of aliphatic hydrocarbons further developments are likely as new strains of these bacteria are isolated. 

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