Microbial mechanisms

K. L. Chase, R. S. Bryant, T. E. Burchfield, K. M. Bertus, and A. K. Stepp. Investigations of microbial mechanisms for oil mobilization in porous media. In E. C. Donaldson, editor. Microbial enhancement of oil recovery Recent advances Proceedings of the 1990 International Conference on Microbial Enhancement of Oil Recovery, volume 31 of Developments in Petroleum Science, pages 79-94. Elsevier Science Ltd, 1991. 

Ma K, Qiu Q, Lu Y. Microbial mechanism for rice variety control on methane emission from rice field soil. Global Change Biol. 2010 16 3085-3095. 

Gadd GM (2000) Bioremediation potential of microbial mechanisms of metal mobilization and immobilization. Curr Opinion Biotechnol 11 271-279... 

Murray, H.W. and Nathan, C.F., Macrophage microbial mechanisms in vivo Reactive nitrogen versus oxygen intermediates in the killing of intracellular visceral Leishmania donovani, J. Exp. Med., 189, 741, 1999. 

Coupled with the fact that microbial systems have been conclusively shown to dechlorinate chlorinated. v-triazuics, it is likely that the role of microbial dechlorination was largely underestimated. For example, in a comparison of sterile and nonsterile soils from the vadose and saturated zones of soil profiles, it was concluded that microbial mechanisms, more than any other, contributed to the formation of hydroxyatrazine in the unsaturated surface soil (Kruger et al., 1997). 

The wide array of nomenclature used to describe disease suppression in agricultural soils, is matched by an equally wide variety of individual microbial mechanisms postulated to explain these phenomena. However, it should be noted that these mechanisms are fairly presumptive, and, if they occur in vivo, are likely to operate in parallel with each other (Figure 1). 

Figure 8 Schematic representation of three possible microbial mechanisms for mobilization of arsenic oxyanions adsorbed to ferrihydrite surfaces by respiratory reduction. Bottom left Shewanella alga reduces Fe(lll) to Fe(It), thereby releasing As(V) into solution (41). Lower right bacterially reduced electron shuttle molecules pass electrons to solid-phase As(V) and Fe(III) (48). Top Sulfiirospirillum bamesii directly reduces both As(V) and Fe(III) (43).

Various microorganisms and microbial mechanisms are relevant in these industrial processes. Examples are conversion processes of organie substanees, e.g., by baeterial oxygenases. Normally low-molecular-weight aromatie hydroearbons including solvents are converted in these biotransformation processes. ... 

Sand W (1997) Microbial mechanisms of deterioration of inorgatnc substrates A general mechanistic overview. International Biodeterioration Biodegradation 40(2-4) 183—190... 

W. Sand Microbial mechanisms of deterioration—a general mechanistic overview,... 

W. Sand, Microbial mechanisms of deterioration—A general mechanistic overview, Int. Biodeterior. Biodegrad. 40 183-190 (1998). 

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. 

Two other broad areas of food preservation have been studied with the objective of developing predictive models. En2yme inactivation by heat has been subjected to mathematical modeling in a manner similar to microbial inactivation. Chemical deterioration mechanisms have been studied to allow the prediction of shelf life, particularly the shelf life of foods susceptible to nonen2ymatic browning and Hpid oxidation. 

Reverse osmosis membrane separations are governed by the properties of the membrane used in the process. These properties depend on the chemical nature of the membrane material, which is almost always a polymer, as well as its physical stmcture. Properties for the ideal RO membrane include low cost, resistance to chemical and microbial attack, mechanical and stmctural stabiHty over long operating periods and wide temperature ranges, and the desired separation characteristics for each particular system. However, few membranes satisfy all these criteria and so compromises must be made to select the best RO membrane available for each appHcation. Excellent discussions of RO membrane materials, preparation methods, and stmctures are available (8,13,16-21). 

These organisms have been used frequently in the elucidation of the biosynthetic pathway (37,38). The mechanism of riboflavin biosynthesis has formally been deduced from data derived from several experiments involving a variety of organisms (Fig. 5). Included are conversion of a purine such as guanosine triphosphate (GTP) to 6,7-dimethyl-8-D-ribityUuma2ine (16) (39), and the conversion of (16) to (1). This concept of the biochemical formation of riboflavin was verified in vitro under nonen2ymatic conditions (40) (see Microbial transformations). 

Biofilms can promote corrosion of fouled metal surfaces in a variety of ways. This is referred to as microbiaHy influenced corrosion. Microbes act as biological catalysts promoting conventional corrosion mechanisms the simple, passive presence of the biological deposit prevents corrosion inhibitors from reaching and passivating the fouled surface microbial reactions can accelerate ongoing corrosion reactions and microbial by-products can be directly aggressive to the metal. 

Nonoxidizing Antimicrobials. Nonoxidizing antimicrobials usually control growths by one of two mechanisms. In one, microbes are inhibited or killed as a result of damage to the ceU membrane. In the other, microbial death results from damage to the biochemical machinery involved in energy production or energy utilization. 

J. R. Knowles in E. E. Hahn, Antibiotics FT (Modes and Mechanisms of Microbial Growth Inhibitors] Springer-Vedag, New York, 1983, pp. 90-107. 

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