Decomposition microbial

G. S. Sayler, Microbial Decomposition of Chlorinated Aromatic Compounds, USEPA 600/2-86/090, Washington, D.C., 1986. 

Once in the soil solution, urea—formaldehyde reaction products are converted to plant available nitrogen through either microbial decomposition or hydrolysis. Microbial decomposition is the primary mechanism. The carbon in the methylene urea polymers is the site of microbial activity. Environmental factors that affect soil microbial activity also affect the nitrogen availabiUty of UF products. These factors include soil temperature, moisture, pH, and aeration or oxygen availabiUty. 

CDU in pure form is a white powder. It is made slowly available to the soil solution by nature of its limited solubihty in water. Once in the soil solution, nitrogen from CDU is made available to the plant through a combination of hydrolysis and microbial decomposition. As with any CRE which is dependent on microbial action, the mineralization of CDU is temperature dependent. Product particle size has a significant effect on CDU nitrogen release rate. Smaller particles mineralize more rapidly because of the larger surface contact with the soil solution and the microbial environment. The rate of nitrogen release is also affected by pH because CDU degrades more rapidly in acidic soils. 

When considering the availability of nutrients, it is also necessary to examine the significance of nutrient re-use within the waterbody. These internal sources amount not to an additional load, but a multiplier on the recyclability of the same load. This nutrient recycling and the internal stores from which they are recycled are often misunderstood, but there is a dearth of good published data about how these recycling mechanisms operate. Microbial decomposition in the water column is one of several internal loops recognized in recent years, but these are not closed and the flux of nutrients recycled through them is delayed rather than retained. 

When we consider sources of methane we have to add "old" methane, methane that was formed millions of years ago but became trapped beneath the earth s surface, to the "new" methane just described. Firedamp, an explosion hazard to miners, occurs in layers of coal and is mostly methane. Petroleum deposits, formed by microbial decomposition of plant material under anaerobic conditions, are always accompanied by pockets of natural gas, which is mostly methane. 

In areas where particular crops are grown continuously, decreases in production with time have been noted. The condition is usually species speciAc, and the disorders which result are frequently referred to as soil-sickness or replant problems. Fruit trees are especially sensitive and the problem has been encountered with apples, peaches, grapes, cherries, plums, and citrus. In most situations, phytotoxicity has been related to the formation of toxic materials as a consequence of the microbial decomposition of plant remains. 

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... 

Child, A.M. 1995 Towards an understanding of the microbial decomposition of archaeological bone in the burial environment. Journal of Archaeological Science 22 165-174. 

The soil analysis is presented in Table II. Small amounts of 2,4-D and 2,4,5-T were detected in soil samples receiving these herbicides. Background values from the control soils were subtracted from the observed values in treated soils. The samples were not corrected for recovery since it was better than 80% for the method. Residues decreased with time after application. Leaching and microbial decomposition could account for this observation. 

All organic chemicals are, by definition, based on chemicals derived from living matter. Thus, the ten highest-volume commercial organic chemicals are all made from starting materials obtained from petroleum (oil) and natural gas, which are believed to have been formed by the microbial decomposition of ancient marine plants and animals. 

Rott B, S Nitz, F Korte (1979) Microbial decomposition of sodium pentachlorophenolate. 7 Agnc Food Chem 27 306-310. 

It seems most likely that the presence of the styrene compound was at least partially responsible for the inhibition of prickly sida germination and root length, since ferulic acid alone (prickly sida seed without carpels plus ferulic acid) had no effect on prickly sida germination or root length (Table XI). The decarboxylation of phenolic acids to corresponding styrenes is known from studies on fungi and bacteria (60, 61). However, in a number of studies directly concerned with the microbial decomposition of ferulic acid, as well as other phenolic acids, no mention is made of any styrene compounds produced as a result of phenolic acid decarboxylation (62, 63, 64, 65). 

Since lignins are polymers of phenolics and are major plant constituents with resistance to microbial decomposition, they are the primary source of phenolic units for humic acid synthesis (178, 179). Once transformed, these humic acids become further resistant to microbial attack and can become bound to soils (180) form interactions with other high molecular weight phenolic compounds (ex. lignins, fulvic acids) and with clays (181) and influence the biodegradation of other organic substrates in soils (182, 183). 

Soil minerals play a stabilizing role in organic matter. The Al and Fe that complex and stabilize organic matter against microbial decomposition are released from soil minerals during soil formation. The supply rates apparently control the content of soil organic matter to a great extent. This is demonstrated by the relationship between pyrophosphate-extractable C and pyrophosphate-extractable Al plus Fe (Wada 1995). 

Wang, D.S., R.W. Weaver, and J.R. Melton. 1984. Microbial decomposition of plant tissue contaminated with arsenic and mercury. Environ. Pollut. 34A 275-282. 

The biogeochemical cycling in different ecosystems is to a large extent determined by biota, especially by the primary production of plants and by microbial decomposition. At present we recognize the development of the intensive biogeochemical investigations of a large number of ecosystems in North America, Europe, Asia and South America. 

Schaumberg et al. [58] made a qualitative infrared spectroscopic study of water-soluble compounds extracted from sewage sludge/oil mixtures which were being incubated in the laboratory for 100 weeks at 25°C, and the results are presented. It was found that there was a pattern to the microbial decomposition of anaerobically-digested sewage sludge which involved the disappearance of carbohydrate, protein, sulphonate, and/or sulphate compounds, coupled with the appearance of carboxylates and nitrates. 

Since methane is produced mainly by microbial decomposition of dead organic matter in swamps, bogs and refuse piles, the close correlations between changes in methane, C02, and temperature suggest that biological processes are involved. 

As to the origins of the major N compounds identified, it is possible that at least a portion of some of these compounds are pyrolysis products of amino acids, peptides, proteins, [18] and porphyrins (a component of chlorophyll), [19] or originate from the microbial decomposition of plant lignins and other phenolics in the presence of ammonia. [20] Of considerable interest are the identifications aromatic and aliphatic nitriles. Nitriles can be formed from amines with the loss of 2 H2, from amides with the loss of H20, and also by reacting n-alkanoic acid with NH3. [21] The detection of long-chain alkyl- and dialkyl-nitriles points to the presence in the soil or SOM of long-chain amines... 

Sundman, V., T. Kuusi, S. Kukanen, and G. Carlberg Microbial Decomposition of Lignins. Acta Agricultiirac Scand. 14, 229—248 (1964). 

Weber, J.B. and Coble, H.D. Microbial decomposition of diquat adsorbed on montmorillonite and kaolinite clays, J. Agric. 

Fig. 8.41 Simulated Chernobyl Cs+ distribution in the soil ecosystem (A) in leaf pads and (B) in soil columns when the microbial decomposition of the organic material is enhanced by an increase in ambient temperature. (Tengen et al. 1991)...

An equation that accounts for parathion transport, snbject to both diffnsion and microbial decomposition, can be written as... 

Gerstl Z, Yaron B (1983) Behavior of bromacU and napropamide in soils. 11. Distribution after application from a point source. Amer J Soil Sci 47 478 83 Gerstl Z, B Yaron, Nye PH (1979a) Diffusion of a biodegradable pesticide as affected by microbial decomposition. Soil Sci Soc Am J 43 843-848... 

Ballschmiter K, Scholz C. 1980. Microbial decomposition of chlorinated aromatic substances. VI. Formation of dichlorophenols and dichloropyrocatechol from dichlorobenzenes in a micromolar solution by Pseudomonas species. Chemosphere 9 457-467. 

Many allelochemicals are decomposed in soil, either abiotically (37) or by microorganisms (95-100). Obviously, the attainment of active concentrations of allelochemicals in soil depends on the relative rates of addition and inactivation. It is important to understand also that microbial decomposition of allelochemicals does not necessarily result in a decrease in allelopathic activity. In fact, the reverse may be true. Hydrojuglone is oxidized in soil to juglone, a quinone that is inhibitory to some species at a 10 ° M concentration (101). Isoflavonoids produced by red clover are decomposed to even more toxic phenolic compounds (95) and to repeat, amygdalin from peach roots is changed to hydrogen cyanide and benzaldehyde which cause the peach replant problem (88), and phlorizin from apple roots is decomposed to several phenolic compounds that appear to be responsible for the apple replant problem (100). 

It is revealing to consider microbial decomposition of allelopathic compounds in relation to synergism. As discussed above, partial decomposition of one compound may result in the presence of several active compounds, which may exert synergistic allelopathic effects. Thus, partial decomposition could increase allelopathic activity, rather than decrease it. 

There are numerous reports describing the allelopathic (phytotmicrobial products on crop growth, particularly in conjunction with heavy residues from the previous crop (1-5). The cause of the reduced crop growth has been attributed to the production of a variety of toxic compounds such as phenolic acids, short-chain fatty acids, patulin, and many others (6-9). These compounds may be produced directly or indirectly during the microbial decomposition of organic residues under varying environmental conditions, such as when the soil remains wet over an extended period of time. 

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