Surface Metabolism - clay organisms

Similar N2 fixation has been seen with (H20 + N2)/Ti02 and other metal-doped mineral surfaces, producing  

The extension to amino acid synthesis on surfaces has also been observed with platinised Ti()2 surfaces, with CH4, NH3 and H20 solutions producing glycine, alanine, glutamine, aspartic acid and serine, all photosynthesised and trapped in the resulting layers near to the surface by their charge. 

Taking this one step further, perhaps even an inorganic gene may have been provided by clay mineral sources. Earliest clay samples are of a mineral called montmorillonite that consists of sheets of aluminosilicates in which Fe2+, Fe3+ and Mg2+ are substituted for some of the Al3+, and Al3+ is substituted for Si4+. The oxygen content of the layers does not change and the alternative valencies allow the production of positive and negatively charged layers. Dramatically, Paecht-Horowitz and co-workers showed that the amino acid adenylate could be polymerised with up to 50 units on the montmorillonite surface in aqueous solution. Similar condensation reactions for carbohydrates on hydrotalcite surfaces have 

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The presence of soil complicates metal removal because soils sorb metals strongly and can also affect microbial—metal complexation. Walkeretal. (1989) showed that purified preparations of cell walls from Bacillus subtilis and Escherichia coli (423 to 973 mmol metal/g cell wall) were more effective than either of two clays, kaolinite (0.46 to 37 mmol metal/g clay), or smectite (1 to 197 nmol metal/g clay), in the binding of seven different metals. However, in the presence of cell-wall/clay mixtures, binding was reduced. In summary, there are several parameters that affect metal complexation. These include specific surface properties of the organism, cell metabolism, metal type, and the physicochemical parameters of the environment. 

Bernal and Cairns-Smith proposed that the first metabolic surfaces were provided by crystals of clay, and therefore that life did literally originate in mud, because clays can adsorb a vast range of organic... 

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