Microbial Accumulation

Mandelbrot, B.B. (1982) The fractal geometry of nature. Freemarm, San Francisco Mann, H. Tazaki, K. Fyfe,W.S. Kerrich, R. (1992) Microbial accumulation of iron and manganese in different aquatic environments An electron optical study. In Skinner, H.C.W. Fitzpatrick, R.W. (eds.) Biomineralization processes of iron and manganese. Catena Verlag, Cremlingen-Destedt, Catena Suppl. 21 115-132... 

Mann H. et al. (1992) Microbial accumulation of ion and manganese in different aquatic environments, an elecgtron optical smdy. In Biomineralization of Iron and Manganese, Modem and Ancient Environments (eds. H. C. W. Skinner and R. W. Fitzpatrick). Catena-Verlag, Cremlingen-Destadt, Germany, suppl. 21, pp. 115-132. 

A rather more specific mechanism of microbial immobilization of metal ions is represented by the accumulation of uranium as an extracellular precipitate of hydrogen uranyl phosphate by a Citrobacter species (83). Staggering amounts of uranium can be precipitated more than 900% of the bacterial dry weight Recent work has shown that even elements that do not readily form insoluble phosphates, such as nickel and neptunium, may be incorporated into the uranyl phosphate crystallites (84). The precipitation is driven by the production of phosphate ions at the cell surface by an external phosphatase. 

It will also be important to understand the rhizosphere ecology around the roots of metal accumulating plants fully. Maximizing the bioavailabihty of the contaminant metals in this zone may require the optimization of the microbial communities, or perhaps the addition of soil amendments. There are early indications that such intervention may be beneficial (88), but research in this area is at a very early stage. 

Urea and uracil herbicides tend to be persistent in soils and may carry over from one season to the next (299). However, there is significant variation between compounds. Bromacil is debrominated under anaerobic conditions but does not undergo further transformation (423), linuron is degraded in a field soil and does not accumulate or cause carryover problems (424), and terbacd [5902-51-2] is slowly degraded in a Russian soil by microbial means (425). The half-hves for this breakdown range from 76 to 2,475 days and are affected by several factors including moisture and temperature. Finally, tebuthiuron apphed to rangeland has been shown to be phytotoxic after 615 days, and the estimated time for total dissipation of the herbicide is from 2.9 to 7.2 years (426). 

After recovery of L-lysine, the residual dl-(49) is epimerized to a mixture of the DL and meso isomers, and the latter is subjected to the same decarboxylation step. This reaction is a part of a microbial process in which glucose is fermented by a lysine auxotroph of E. coli to meso- which accumulates in the medium. Meso-(49) is quantitatively decarboxylated to L-lysine by cell suspensions oi erobacteraerogenes (93). However, L-lysine and some... 

The addition of therapeutic or cosmetic agents to dentifrices has paralleled advances in knowledge about factors affecting the human dentition. Agents added to dentifrices can act directly on the host tooth stmcture or on specific oral accumulations, for example, the principal action of fluoride is on the tooth enamel. The primary action of an abrasive, however, is on an accumulated stained pellicle. Oral accumulations of interest to preventive dentistry are dental pellicles, dental plaque, dental calculus (tartar), microbial populations responsible for oral malodor, and oral debris (food residues, leukocytes, etc). Plaque is most important because of its potential to do harm. 

Ethanol fermentation is a particularly good example of product accumulation inhibiting the microbial culture. Most strains of yeast have a much slower alcohol production rate when ethanol reaches about ten percent, and the wine or said strains that achieve over 20 percent by volume of ethanol are very, very slow. A system known as the Vacuferm for removal of alcohol by distillation as it is formed is... 

Wastage is caused by biological material accumulating on or near surfaces. Microbial mats such as slime layers and massive accumulations of larger organisms cause most damage. 

From the mechanistic point of view three basic principles of microbial resistance to drugs are known inactivation of the drug, alteration of the target, and reduced drug accumulation at the target site. However, several variations on these themes are known. 

Another contaminant of concern for the Delta is Se. Selenium occurs in high concentrations in the soils of the western San Joaquin Valley associated with salts that have accumulated in this region [10]. Selenium is recycled through agricultural retom flows to the river and transported to the Delta and San Francisco Bay. The Se is transformed into a more bioavailable form by microbial communities and aquatic plants. The Se is passed through the foodweb with particular concern for bottomfeeding migratory waterfowl and predatory fishes. The hydrodynamics of water from the San Joaquin River is an important consideration in the intensity and distribution of Se contamination within the Delta. 

Particulate, as well as microbial, contamination must be guarded against when sterile products are being manufactured. Thus, walls, ceilings and floors should possess smooth, impervious surfaces which will (i) prevent the accumulation of dust or other particulate matter and (ii) allow for easy and repeated cleaning and disinfection. For the same reasons, where walls and floors or ceilings meet, covings should be used. 

Transgenic E. coli accumulate comparatively low levels of carotenoids " compared to microbial algae, yeasts, and bacteria. Many efforts ° have focused on increasing accumulation by manipulation of factors affecting metabolic flux and metabolite accnmnlation (listed and discnssed in Sections 5.3.1.1 and 5.3.1.3 A) and have been reviewed." - " In bacterial systems, approaches to control can be categorized as either infrastructural (plasmids, enzymes, strains) or ultrastructural (media and feeding, enviromnent, precursor pools, substrate flux). 

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