Organic matter metabolism

Biofilms enhance bacteria-DOM interactions by several means. Their spatial and chemical heterogeneity provides additional sorption sites for DOM compared with clean surfaces. Their loose architecture with interstitial voids and channels increases diffusivity and to some extent allows convective flow within biofilm structures. Because bacteria metabolize organic matter sorbed to the biofilm, a diffusion flux from the free water to the biofilm is maintained. Large proportions of organic matter sorbed to the biofilm are not instantly turned over but remain in the biofilm as a reservoir, which buffers direct effects of DOM depletion in the water column. 

The oxidation of organic matter in anaerobic sediments can utilize a number of species as oxidants, of which sulfate is the most important. In seawater at pH values close to 8, sulfate-reducing bacteria metabolize organic matter according to the following simplified equation ... 

Heterotroph An organism that metabolizes organic matter. Animals and many microbes... 

Biochemical oxygen demand The quantity of oxygen required by bacteria to metabolize organic matter in water. 

The pathway of plutonium dissolved in natural water, from a source such as a nuclear facility, to man, may be quite complicated. During the transport, the plutonium atoms encounter dissolved and particulate inorganic and organic matter, as well as minerals in rocks, sediment and soil, and living organisms which may metabolize the plutonium. Figure 1 depicts some of the more essential routes for plutonium between the point of emission and the plutonium consuming man. The overall effect of these pathways is that plutonium is slowly eliminated from the water, so that only a minor fraction of it reaches man. An example of this is that of the 4.2 tonnes of plutonium deposited on the earth after... 

It is less conunonly known that methane was one of the original atmospheric gases and is a normal product of the microbial decomposition of organic matter under anaerobic conditions. Bacteria involved in production of methane are unique in their metabolism and other properties. The balanced... 

Inputs of organic matter and nutrients, benthic metabolism, and nutrient retention at each stream section depend on diffuse and point sources. Yet, under low flow conditions, water and matter transport downstream becomes impeded or discontinued due to stream contraction and fragmentation during dry periods. Therefore, nutrient export from rivers in semiarid regions will depend, more so than in more humid regions, on the interplay between the spatial configuration of organic matter... 

Stable metabolic associations generally between pairs of anaerobic bacteria have been termed syntrophs, and these are effective in degrading a number of aliphatic carboxylic acids or benzoate under anaerobic conditions. These reactions have been discussed in reviews (Schink 1991, 1997 Lowe et al. 1993) that provide lucid accounts of the role of syntrophs in the degradation of complex organic matter. Two examples are given here to illustrate the experimental intricacy of the problems besetting the study of syntrophic metabolism under anaerobic conditions ... 

Apart from its use in studies of nitrogen fixation, N-labeled substrates have been used to assess the association of contaminants with organic matter in soil, and in metabolism. 

Minimization of agricultural losses from soil toxins Toxins from soils appear to be responsible for inhibition of nitrogen fixation, metabolism and nodulation in legumes. Removal of toxins could be achieved by proper adsorption techniques and also by growing companion plants that contribute organic matter to microoranisms which help to destroy or degrade toxic chemicals. 

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